Monday, February 01, 2010

Half Sigma's flawed post on DTNBP1   posted by ben g @ 2/01/2010 10:33:00 AM

A while back, Mark and I were working on a comprehensive post which would try to tally the results of the various IQ-gene studies to see what they said about racial differences. We began this quest bright-eyed and hopeful that we would help contribute to ending a calamitous debate that has gone on for way too long. However, as we learned more about genetics, and these studies in particular, we came to realize that it's too early to take IQ-genes seriously.

We began with an approach similar to what Half Sigma did 2 years ago with the DTNBP1 gene. However, we soon learned that this approach was incredibly flawed and misleading. I wasn't going to write this post, but recently Half Sigma's DTBP1 post was linked from Reddit and tens of thousands of people are viewing it. When I saw that, I frustratedly criticized HS. He responded that I should give a more diplomatic and reasoned response, so here it is:

  1. You cannot simply add up SNPs from the same gene or chromosome. Half Sigma simply adds the observed effects of the SNPs to one another, ignoring that the alleles are highly correlated with one another, and not independently inherited, which is referred to as linkage disequilibrium (LD). The study that Half Sigma used provides the following table of LD for its SNPs:


    As can be seen in this table, pairwise LD goes as high as 1.0, meaning that two of the alleles are always inherited together. Adding these SNP's together is therefore like counting them twice.

  2. Group comparisons require replication in both groups. Because different populations have systematic genetic and environmental differences, an effect in one group may not occur in another. The study that Half Sigma uses relies primarily on a (small) sample of Dutch people. It is unclear whether these effects would exist in a population of African ancestry, let alone another European one.

  3. Candidate-gene association studies are not reliable. This is the most important point. Candidate gene association studies have largely failed to replicate. In fact, there have been no common IQ polymorphisms which have been replicated. Genome-wide association studies, which don't suffer as severely the various biases of candidate-gene association studies like publication bias or the winner's curse have not shown common SNP-associations with IQ.

    IQ is highly heritable, so the problem is the current methods, not the search for genes. With the development of sequencing technology and huge cohorts, we will be able to see the genes that are really behind normal IQ variation. With replication in multiple ethnicities and races, we will also see to what extent various genes and environments are responsible for group differences. There's no need to make proclamations of victory for hereditarianism or environmentalism in the mean time.

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Tuesday, December 08, 2009

Does the family matter for adult IQ?   posted by ben g @ 12/08/2009 05:57:00 AM

A frequent claim in the IQ debates is that which family you are raised in has no lasting impact on your IQ. Jensen argues in The g Factor that the only causes of IQ similarities between adult identical twins are genetic. Many researchers go so far as to argue that by 12 years of age, the shared environment has no impact.

Based on my limited knowledge of the behavior genetic research, I used to hold this position as well. But thanks to some recent in depth reading, I have come to the conclusion that which family you are raised in matters significantly for your IQ as an adult, especially so for people of lower socioeconomic status. I'll detail the behavior genetic evidence here, and argue that it points to significant shared environmental influences on adult IQ scores.

Twin Studies

The most recent and comprehensive survey of twin studies on IQ comes from Haworth et al (2009). Using pooled twin data from around the world, they modeled genetic and environmental influences as a function of age. Here is what they found regarding the effects of the shared environment:
[S]hared environment shows a decrease from childhood (33%) to adolescence (18%) but remained at that modest level in young adulthood (16%).
In an email exchange with Dr. McGue (one of the co-authors of the paper) he told me that while the latest data may not fit with earlier estimates, it's actually more reliable due to the unprecedented sample size (11,000 pairs of twins).

One failing of this study, though, is that it doesn't go far enough into adulthood. The young adult group ranges from 14 to 34 years of age, with an average age of 17. In contrast, McGue (1993) looked seperately at data on adults over 20 years of age. He found that the shared environment diminished to zero impact at that point. Here's his chart:
Looking at that chart, you might quickly conclude that shared environmental influence evaporates by age 20. However, this conclusion is premature. Twin studies make a great number of assumptions, some of which increase and others of which decrease estimates of the shared environment. A straightforward way of bypassing these assumptions is to compare monozygotic twins reared apart (MZAs) to monozygotic twins reared together (MZTs). The following data comes from a comparison of MZTs and MZAs, of average age 41, in Bouchard (1990):

MeasureMZA correlationMZT correlation
WAIS IQ-Full Scale0.690.88
WAIS IQ-Verbal0.640.88
WAIS IQ-Performance0.710.79

Differences between MZA's and MZT's on Raven's Progressive Matrices follow the same pattern but are even more extreme. Bouchard (1981) reported a median correlation of only 0.58 for adult MZA's on the Raven's. Curiously, though, MZA's are equally if not more correlated than MZT's on the Mill-Hill vocabulary test. Apparently, the pattern is that more g-loaded tests tend to show stronger evidence of lasting shared environmental impact.

It's worth noting that MZT vs. MZA comparisons are actually biased towards an underestimation of shared environmental impact. Bouchard's study of twins reared apart found an environmental correlation of .22 for MZAs on various environmental measures, with some having a small but significant correlation with IQ scores. Also MZA's share the womb. To summarize: when the assumptions of the twin method are effectively controlled for, lasting shared environmental impacts are revealed.

Adoption Studies

To date, most adoption studies of IQ have concluded that being adopted by a new and typically well-off family has no effect on adult IQ scores. Here is a chart of adoption studies from Bouchard (2009):As you can see by clicking it, the IQ correlation between unrelated individuals in the same family decreases (on average) from .26 in childhood to .04 in adulthood (which begins at age 17 for the purposes of this graph).

However, as with the previous chart, the quick conclusion that shared environmental influences don't matter in adulthood shouldn't be so quickly accepted. To begin with, we can see that the adoption data underestimates the shared environment relative to the twin literature. This most likely occurs because of the assumptions that go into adoption studies.

Stoolmiller (1999), for example, highlighted the issue of range restriction-- the idea that the limited range of adoptee and adoptive family environments will lower estimates of the shared environment. This idea is supported by studies which make the extra effort to include individuals of lower SES. The French adoption studies that made such an effort buck the trendline seen above, in finding that nurture matters almost as much as nature for the IQ of 14 year olds. Scarr (1993) is the outlier in the adoption graph above, finding a .19 correlation between unrelated adolescent siblings. Perhaps her results differed from others because her sample was multi-racial and therefore less range restricted. Lastly, there are other lines of evidence supporting the idea of range restriction, such as Turkheimer's work on SES and cognitive ability.

It's worth noting, however, that McGue (2007) looked for evidence of range restriction effects within the "broad middle class" and did not find any. He used statistical methods that are over my head to estimate the effects of range restriction based on a range restricted sample and state census data. Unfortunately there are no studies which have critiqued his as of yet. Any commenters who are familiar with the statistics involved are invited to comment. Even if McGue is right about restriction of range, my point stands that assumptions inherent in the adoption studies deflate c^2 estimates.

Future Directions

Future work will help sort out the still unanswered question of shared environmental influences on adult IQ scores. There are large longitudinal adoption studies currently under way, and I believe that Haworth's twin study will be followed-up on and include data on older twins. There are also interesting (albeit less methodologically agreed upon) studies coming out like this one, which find significant shared effects on IQ in adulthood.

My reading of the available evidence is that there is a significant shared environmental input to adult IQ, and that it is associated with socioeconomic status. To what extent it's the neighborhood or the parents themselves that matters is unclear. Just as the most g-loaded tests show the most shared environmental effects in the MZA-MZT comparison, so too does the Flynn effect occur on the most g-loaded tests, suggesting that whatever is loading onto the "shared environment" within generations is also responsible for differences between them.

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Saturday, November 21, 2009

Models of IQ & wealth   posted by Razib @ 11/21/2009 05:48:00 PM

Steve Hsu has been interesting of late (interesting like Steve, not Malcolm). So, IQ, compression and simple models and If you're so smart, why aren't you rich?. For a theoretical physicist I find Steve to be eminently clear in his exposition of abstract topics (perhaps he has practice from having to talk to experimental physicists?).


Sunday, November 08, 2009

The quest for common variants & cognition   posted by Razib @ 11/08/2009 11:39:00 AM

A genome-wide study of common SNPs and CNVs in cognitive performance in the CANTAB:
Psychiatric disorders such as schizophrenia are commonly accompanied by cognitive impairments that are treatment resistant and crucial to functional outcome. There has been great interest in studying cognitive measures as endophenotypes for psychiatric disorders, with the hope that their genetic basis will be clearer. To investigate this, we performed a genome-wide association study involving 11 cognitive phenotypes from the Cambridge Neuropsychological Test Automated Battery. We showed these measures to be heritable by comparing the correlation in 100 monozygotic and 100 dizygotic twin pairs. The full battery was tested in 750 subjects, and for spatial and verbal recognition memory, we investigated a further 500 individuals to search for smaller genetic effects. We were unable to find any genome-wide significant associations with either SNPs or common copy number variants. Nor could we formally replicate any polymorphism that has been previously associated with cognition, although we found a weak signal of lower than expected P-values for variants in a set of 10 candidate genes. We additionally investigated SNPs in genomic loci that have been shown to harbor rare variants that associate with neuropsychiatric disorders, to see if they showed any suggestion of association when considered as a separate set. Only NRXN1 showed evidence of significant association with cognition. These results suggest that common genetic variation does not strongly influence cognition in healthy subjects and that cognitive measures do not represent a more tractable genetic trait than clinical endpoints such as schizophrenia. We discuss a possible role for rare variation in cognitive genomics.

David Goldstein is one of the authors. I wonder if this influenced his views on the evolution of intelligence.

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Tuesday, July 28, 2009

Genetics in The Atlantic   posted by Razib @ 7/28/2009 03:58:00 PM

A reader points out that David Shenk is blogging genetics & IQ over at The Atlantic. If you have some free time to kill in comment sections, you might be interested. To get a flavor, a post titled The Truth About IQ has a footnote to Stephen Jay Gould's Mismeasure of Man.


Saturday, July 18, 2009

IQ & heart disease   posted by Razib @ 7/18/2009 10:21:00 PM

IQ Explains Some Of The Difference In Heart Disease Between People Of High And Low Socio-economic Status:
Authors of the study published in the European Heart Journal on 15 July...analysed data from a group of 4,289 former soldiers in the USA. They found that IQ explained more than 20% of the difference in mortality between people from socio-economically disadvantaged backgrounds compared to those from more advantaged backgrounds. Importantly, this was in addition to the classical, known risk factors for heart disease, such as smoking and obesity.
"The difference between the second and third analyses showed that IQ alone explained a further 23% of the differences in mortality between the higher and lower ends of the socio-economic spectrum, in addition to the other, known risk factors," said Dr Batty. “IQ wasn’t a magic bullet in this study, but this psychological variable had additional explanatory power on top of the classic variables such as smoking, high blood pressure, high blood glucose and obesity. It has partially explained the differences in death from heart disease and all causes."
...there could be three possible explanations for Dr Batty's findings: "(i) intelligence might lead to greater knowledge about how to pursue healthy behaviours; (ii) intelligence may "cause" socioeconomic position, i.e. more intelligence leads to more education, income, occupational prestige . . .; and (iii) intelligence may be a marker for something else, and it is that something else, early life exposures, for example, that leads to mortality."....

When correlations between socioeconomic status and health outcomes emerge, generally there is an assumption that the differences are due to disparate access to health care, or, more vaguely to the mysterious effect of low social status on someone's health. Matt Ridley actually posited the second explanation in Genome. As noted above intelligence does not explain everything, but its role is unfortunately not considered all too often. If, for example, intelligence has some correlation with time preference, and time preference modulates one's risk calculus, the causal chain which might result in disparate health outcomes is obvious. In The Myth of the Rational Voter Bryan Caplan has a reasonable number of references to the literature which show that the more intelligent may not be particularly rational in any absolute sense, but they are far more rational than the conventionally dull in a relative sense.

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Tuesday, June 09, 2009

A systematic literature review of the average IQ of sub-Saharan Africans   posted by ben g @ 6/09/2009 01:30:00 PM

A study from Wicherts et al published online in the journal Intelligence today:

On the basis of several reviews of the literature, Lynn... concluded that the average IQ of the Black population of sub-Saharan Africa lies below 70. In this paper, the authors systematically review published empirical data on the performance of Africans on the following IQ tests: Draw-A-Man (DAM) test, Kaufman-Assessment Battery for Children (K-ABC), the Wechsler scales (WAIS & WISC), and several other IQ tests (but not the Raven's tests)... Results show that average IQ of Africans on these tests is approximately 82 when compared to UK norms.

UPDATE: Tables and Figures below the fold

Table 4. Results by subsets of samples.

Table 5. Estimates of mean IQs per country on the basis of studies in Table 2 and studies from the Raven's study.

Fig. 1. Scatterplot of data from study by Lynn (2006) and Lynn and Vanhanen (2006).

Fig. 2. Scatterplot of data from study by Rindermann (2007).

Fig. 3. Scatterplot of data from study by Lynn and Mikk (2007).

Fig. 4. Scatterplot of data from study by Lynn et al. (2007).

Fig. 5. Mean of samples that meet our inclusion criteria against the inverse of the standard error.

Fig. 6. Mean of samples from studies published prior to 2006 against the inverse of the standard error.


Tuesday, May 05, 2009

An education bubble? Data from the explosion of AP tests   posted by agnostic @ 5/05/2009 12:38:00 AM

A simple but powerful way to determine whether or not there's a irrational bubble is to look for a lot of people who are participating in a trend who have no business doing so. For instance, a Mexican strawberry-picker making $15,000 a year who gets a $720,000 loan for a home. If these don't-belong-there people make up a larger and larger fraction of all who get loans, that strongly suggests that everyone is trying to get in on a speculative bubble -- and that the gatekeepers of the activity are increasingly debauching their entry standards to accommodate the losers.

One datum that suggests an irrational bubble in education is that a much larger fraction of the population is going to college now, and that not surprisingly the average IQ of college students has declined by about 2/3 s.d. -- admissions boards began to scrape deeper down into the sludgebucket of society.

How about looking even earlier? High school is compulsory, so we can't really use high school enrollment to judge whether there's a bubble or not. But what about the sub-group of high school that ostensibly is there to prepare college-bound students for college? That is up to the choice of students, perhaps being bullied by their parents. There is strong evidence even at this early stage of an irrational bubble.

What got me thinking about this was a recent NYT article on how teachers feel about the Advanced Placement program, which is based on a report from the Thomas B. Fordham Institute. The key item that popped out was the claim that participation in the AP program has exploded in recent years, and that this has made a fair fraction of teachers anxious about whether there are students there who shouldn't be. This sure smells like a bubble.

First, let's make sure that the AP program really is exploding as they say, and then we'll see if there's a rational basis for it or not. To measure participation in the AP program, I simply took the number of AP tests taken and divided it by the high school population size. (The AP data are here, and the high school pop data are here, Table A-1.) The AP data go back to 1988, while the high school pop data end in 2007, so I looked at the period from 1988 to 2007. Here are both the total number of AP tests taken and the per capita rate:

An exponential trend accounts for 99.8% of the year-to-year variation for the total number of tests taken, and 99.2% in the per capita case. So, clearly participation in the AP program has been exploding at least since 1988.

Now, is there a sound basis for this increase -- like, maybe kids these days are just getting exponentially smarter? Without looking at the data, we know this is wrong since the main determinant of doing well in AP classes is IQ, and that is influenced mostly by genes and unpredictable aspects of the environment, which haven't been changing so rapidly from one year to the next.

Turning to data on how well 17 year-olds are doing academically, let's look at some tables from the 2007 version of the Digest of Education Statistics (all under Chapter 2, and then Educational Achievement). Table 112 shows that on the National Assessment of Educational Progress, the average reading score for 17 y.o.s did not change from 1971 to 2004. Table 115 shows that the percent of 17 y.o. students who are at the 300 level or above in reading did not change from 1971 to 2004. Tables 125 and 126 show the same lack of change for math skills tested by the NAEP. Table 135 shows that the average Critical Reading score on the SAT did not change from 1988 onward -- indeed, it was steady back to about 1976, and had been declining before then. There was a modest uptick in Math scores (15 points, or 0.15 s.d.). The Critical Reading or Verbal score is more highly g-loaded than the Math score for the SAT, or is a better measure of IQ, which means the apparent uptick in Math scores may not mean as much as we'd think.

Taken together, these data show that the academic fundamentals of high schoolers has not changed since the 1970s. If there has been no upswing at all in the fundamentals -- let alone an exponential one -- then the explosion of the AP program is accounted for completely by irrational factors. It seems just like the housing bubble -- the size of deserving borrowers didn't explode, so the surge in borrowing must have been due to a bunch of undeserving people pouring into the building, namely low-income people. Here are two graphs showing that this happened in the AP program too:

The first shows the distribution of AP scores, where 5 is greatest. You can check the numbers for yourself in the previous link to the AP data, but there has been no change in the percent of all tests that received a score of 4 or 5 -- there have not been more and more smarties piling into AP classrooms, at least not since 1988. Therefore, everyone who deserved to be there was already there. However, the percent of all tests receiving a score of 1 -- telling the student, "why did you even bother?" -- has doubled from 10% to 21%. Those receiving a 2 shrunk a tiny amount, from about 23% to 21%. But those receiving a 3 declined from about 32% to 24%. This means that, unlike for smarties, more and more dummies have been allowed into the AP program.

This is reflected in the change in the mean and standard deviation of test scores: keeping the smarties fixed while adding a lot more dummies will drag down the mean and increase the heterogeneity or variance. That's analogous to the housing bubble causing a decline in the mean creditworthiness of the population of borrowers, and an increase in their heterogeneity, as both the sound and the unsound begin to rub shoulders in loan offices. And just as lenders increasingly cheapened their standards by not requiring down payments or proof of income, so high school teachers and administrators have allowed increasingly ill-prepared -- stupid -- students into the AP program.

In sum, there is very strong evidence from AP tests for a speculative bubble in education. Most of what I've read on whether or not such a bubble exists has focused on college -- soaring tuition, more and therefore dumber students, and so on. These data, though, show that the mania extends even to high school, not just higher ed. For at least the past five years, there have been many news stories about competitive admission to pre-school, so perhaps someone could dig up some numbers to show an exponential increase there too that can't be rationalized by a change in fundamentals. In any case, it's clear that this bubble is much more general than the college data suggest.

Curiously, the phrase "education bubble" has not appeared at all in the NYT, although it has appeared many times in the blogs that the newspaper hosts. Googling the phrase gets 39,000 hits. Rises and falls in tuition get plenty of coverage, but that doesn't show that the reporters are aware of the irrational bubble -- they just think it's unfair, that college should be cheaper so that more can attend. But just as no one was allowed to say that most low-income borrowers were undeserving of home loans since they were disproportionately black and Hispanic, so we aren't allowed to say that a lot of college students are nowhere near being "college material" -- that would violate the "demotic life and times," as Jacques Barzun has dubbed the zeitgeist from roughly the 1960s until today. We cripple our minds by imbibing political correctness.

The bursting of the education bubble may be decades away -- it sure has been going on for awhile, so its period may be much longer than that of the housing or stock market bubbles. Let's just hope that when it happens, it will turn out that hedge funds and investment banks won't have exposed themselves to all of this silliness, and that we won't be plunged into another multi-year recession.

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Monday, May 04, 2009

IQ matters when it matters   posted by Razib @ 5/04/2009 05:42:00 PM

As many have noted, The New Republic is now publishing perceptions that Sonia Sotomayor is not that intelligent. Granted, even if affirmative action played a role in her acceptance to Princeton and Yale law school, the fact that she graduated and passed the bar suggests a minimum threshold of ability. But that's not good enough, it seems that many liberals would like someone who can go toe-to-toe with the conservatives on the court intellectually, and she doesn't pass the grade on that elevated level. When the stakes are high, and a Supreme Court position is arguably one of the most powerful positions within the American government, the perceived marginal returns on more g become stark for those who would pooh-pooh it in other contexts.

Addendum: As noted in the comments, yes, it doesn't take a genius to know how political confederates want you to rule. I happen to think that most moral & political reasoning is really moral & political rationalization. So the key is simply to find people who can argue in a crisp manner in favor of positions they already hold a priori. More generally I accept there is some systematic tendencies in terms of what the smart, as opposed to the dumb, believe, regardless of their ideology. See The Myth of the Rational Voter for examples. But let's not confuse the signal for the noise.

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Saturday, April 18, 2009

Profile of Greg Cochran in The Los Angeles Times   posted by Razib @ 4/18/2009 02:45:00 PM

Steve points me to a profile of Greg & Henry, with a focus on Jewish genetics & smarts.

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Thursday, April 16, 2009

IQ and "conventional wisdom"   posted by Razib @ 4/16/2009 11:19:00 PM

Several people have emailed me (and emails and forward are appreciated by the way) about two articles in The New York Times about IQ. IQ Harmed by Epilepsy Drug in Utero, which Steve's already commented on. And the most emailed article currently, Nicholas Kristof's How to Raise Our IQ. Some of you who have been reading this blog since the beginning might have noticed that I long ago stopped talking much about psychometrics. Why? I'd rather not waste my time trying to convince smart people that they are actually smarter than stupid people. If I had a penny every time someone with an elite college education in the hard sciences explained that "they don't believe in IQ".... Of course, on the other hand these aren't the huge majority of people. Many who were nerds or of high intelligence know that there's a qualitative difference between themselves and the herd, in particular those from families with several siblings where psychometric variance is rather obvious. How much more "shared" can environment exactly get?

But in any case, many of the intelligent refuse to assent to the position that intelligence actually exists, and that it can be measured. A few conversations aren't going change opinions here, as the opinions aren't based on empirical data. Rather, it's a theory to which one is socialized (and which socialization can reverse, but this requires a great deal of time investment which isn't going to happen with most people). My own experience with the crowd that runs with Robin Hanson and Eliezer Yudkowsky is that 1) they tend toward the retarded end of social intelligence 2) are invariably accepting of, or open to, the reality of g. In other words, my assumption is that most people who "don't believe in intelligence," don't for reasons of socialization, because they know the rewards built into the incentive structure of human groups for conformity. Of course, there is "believe," and then there is believe. The same people who don't believe in intelligence are proud of their GRE scores, convinced that Republicans and religious people have lower IQs, and outraged when the mentally deficient, as measured on IQ tests, are executed. This probably reflects some mental modularity. People might say they don't believe in IQ, but the decisions they make are to some extent informed by the assumption that intelligence exists, and individuals vary. This shouldn't be a surprise, our executive functions have only a loose control over the different subfunctions which define our cognition. Ironically it might reflect the limits of the conscious rationalin enforcing its well on subconsciously operating modules. The long arm of intelligence reaches only so far into the crevasses of one's mind.

So the best way to increase the intelligence of your offspring? Fuse your gametes with someone intelligent! You don't even have to believe in intelligence to do this, as many who do just this don't. The main issue isn't that people won't be a position to fuse their gametes with individuals in the same range as themselves in terms of intelligence. Rather, it's that they won't let the fusion come to fruition!

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Friday, March 27, 2009

Cortical thickness & intelligence   posted by Razib @ 3/27/2009 01:12:00 PM

Follow up to the post below, Jake Young at Pure Pedantry has a thorough review.

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Thursday, March 26, 2009

IQ & neuroscience   posted by Razib @ 3/26/2009 03:21:00 PM

Positive association between cognitive ability and cortical thickness in a representative US sample of healthy 6 to 18 year-olds:
Neuroimaging studies, using various modalities, have evidenced a link between the general intelligence factor (g) and regional brain function and structure in several multimodal association areas. While in the last few years, developments in computational neuroanatomy have made possible the in vivo quantification of cortical thickness, the relationship between cortical thickness and psychometric intelligence has been little studied. Recently, cortical thickness estimations have been improved by the use of an iterative hemisphere-specific template registration algorithm which provides a better between-subject alignment of brain surfaces. Using this improvement, we aimed to further characterize brain regions where cortical thickness was associated with cognitive ability differences and to test the hypothesis that these regions are mostly located in multimodal association areas. We report associations between a general cognitive ability factor (as an estimate of g) derived from the four subtests of the Wechsler Abbreviated Scale of Intelligence and cortical thickness adjusted for age, gender, and scanner in a large sample of healthy children and adolescents (ages 6–18, n = 216) representative of the US population. Significant positive associations were evidenced between the cognitive ability factor and cortical thickness in most multimodal association areas. Results are consistent with a distributed model of intelligence.

See ScienceDaily.


Tuesday, March 17, 2009

Brain & intelligence   posted by Razib @ 3/17/2009 06:55:00 PM

Readers of this weblog from back in 2002 know that we used to point to Paul Thompson's research. So see this, Genetics of Brain Fiber Architecture and Intellectual Performance:
The study is the first to analyze genetic and environmental factors that affect brain fiber architecture and its genetic linkage with cognitive function. We assessed white matter integrity voxelwise using diffusion tensor imaging at high magnetic field (4 Tesla), in 92 identical and fraternal twins. White matter integrity, quantified using fractional anisotropy (FA), was used to fit structural equation models (SEM) at each point in the brain, generating three-dimensional maps of heritability. We visualized the anatomical profile of correlations between white matter integrity and full-scale, verbal, and performance intelligence quotients (FIQ, VIQ, and PIQ). White matter integrity (FA) was under strong genetic control and was highly heritable in bilateral frontal....bilateral parietal...and left occipital...lobes, and was correlated with FIQ and PIQ in the cingulum, optic radiations, superior fronto-occipital fasciculus, internal capsule, callosal isthmus, and the corona radiata...for PIQ, corrected for multiple comparisons). In a cross-trait mapping approach, common genetic factors mediated the correlation between IQ and white matter integrity, suggesting a common physiological mechanism for both, and common genetic determination. These genetic brain maps reveal heritable aspects of white matter integrity and should expedite the discovery of single-nucleotide polymorphisms affecting fiber connectivity and cognition.

Here's the summary at ScienceDaily.

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Tuesday, February 17, 2009

Steven Rose: Wrong on the science of race, gender, and intelligence   posted by ben g @ 2/17/2009 08:13:00 AM

In the latest issue of Nature, competing editorials were written on the proposition that scientists should study race and IQ. Steven Ceci and Wendy Williams argued 'Yes', and Steven Rose argued 'No'. In this article I will detail the scientific errors which underly Rose's argument. The scientific reasons offered by him are largely a veneer meant to justify his "radical science" political views, but I will refrain from commenting on his politics until my next post on this.

Rose argues:
the categories of intelligence, race and gender are not definable within the framework required for natural scientific research, failing my first criterion of being well-founded. They also fail the second criterion of being answerable: we lack the theoretical or technical tools to study them.
Let's begin with his critiques of IQ:

to try to capture the many forms of socially expressed intelligent behaviour in a single coefficient — and to rank an entire population in a linear mode, like soldiers on parade lined up by height — excludes most richly intelligent human activities. Social intelligence, emotional intelligence, the intelligent hands of the craftsman or the intelligent intuition of the scientist all elude the 'g' straightjacket
Modern psychometrics isn't claiming that all of a person's intelligence is measured by IQ or g. IQ is used because of its strong and reliable correlations with educational and economic performance, independent of class and race.

Group comparisons of IQ are even more problematic. Attempts have been made to make 'culture-fair' or 'culture-free' tests, as if such a thing were possible, to allow comparisons of 'g' between people from very different societies.
Rose doesn't understand what is meant by "culture fair." It doesn't mean that the test prevents someone's culture from having an effect on their IQ score. Rather, it means that culture does not effect the test's predictive validity. And that is indeed the case. Worldwide the correlations between IQ and economic/educational success are high.

Rose goes on to critique the concept of biological race:

As for 'race', the problem is whether it is a biologically, as opposed to socially, meaningful category. Among geneticists interested in differences in gene frequencies between populations, there is increasing consensus that the word obscures more than it reveals, and should be replaced by the concept of biogeographic ancestry, which makes possible the study of subpopulations for relevant genetic and phenotypic characteristics... Broad divisions between 'white' or 'Caucasian' and 'black' or 'Asian', the groups generally discussed in the context of the IQ debate, especially in the United States, hide genetically important subpopulation differences within these groups.
To begin with, it is biologically meaningful to talk of the 'white race' or the 'asian race.' These categories encapsulate a great deal of genetic variation, and are not arbitrary; as Steve Sailer has pointed out, Cavalli-Sforza's principal components map corresponds to social categories of race.

Furthermore, discussing higher level categories does nothing to obscure lower level categories. If I know someone is a Christian, this doesn't mean I cease to be interested in their denomination. And in fact, psychometricians do study more specific categories than the big 3 races; see for example Jason Malloy's summary of Lynn's worldwide psychometric work.

As for terminology, it is actually irrelevant whether we refer to population groups by their "race" or their "biogeographic ancestry." The former has more social and historical baggage, and the latter is more long-winded, but they both point to the same empirical fact-- group-based genetic differences.

Lastly, the IQ differences between blacks, whites, and asians interest researchers so much simply because the differences in educational/economic outcomes between these groups interest researchers (and the public) more than other group-based differences.

Rose moves on to gender:

the crucial question is whether it is possible to identify a biological — presumably genetic or neurodevelopmental — cause to any difference in the way men and women think and act. The problem is that from the moment of birth, boys and girls are treated differently, which shapes both their growing bodies and brains and how they are expected to behave... Thus, although there are minor average structural and biochemical variations between Western men's and women's brains (such as the volume of some nuclei and the distribution of hormone receptors), speculations on their implications for how men and women may think or behave lack any empirical basis.
There are plenty of research methods that can be used to sidestep the problems that Rose raises here. To name a few, we can look at: kids raised as the opposite gender because of botched genital operations, how hormones correlate with various behaviors, the differences between girl or boy babies in their first months of life, human universals, etc.

Rose closes up the "scientific" portion of his article by citing many of the difficulties which prevent the resolution of the race and IQ debate:

The standard approach of population biologists to estimating the potential genetic contribution to a trait is to make a heritability estimate. Whatever the strengths and weaknesses of this measure within a population, it is essentially just that: a within-population measure, only valid for a given environment. The nature of the equations means that if the environment changes, the heritability estimate changes too...Even if reliable correlations were found between some intelligence test score and a measure of brain physiology or activity held by a specific group, such a correlation says nothing about the direction of causation.
This is an argument for more research, not less. This is an argument for genome-wide association studies, which will allow us to pinpoint the genes that effect intelligence and how they interact with the enviornment. This is an argument for more research on the neuroscience behind IQ and intelligence. This is an argument for further funding of projects to map out the genetic differences between human populations world-wide. This is not an argument for cutting off an important (albeit, politically inconvenient) avenue of science.

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Monday, December 15, 2008

Low carb diets and cognitive function   posted by Razib @ 12/15/2008 04:19:00 PM

Low-carbohydrate weight-loss diets. Effects on cognition and mood:
To examine how a low-carbohydrate diet affects cognitive performance, women participated in one of two weight-loss diet regimens. Participants self-selected a low-carbohydrate (n = 9) or a reduced-calorie balanced diet similar to that recommended by the American Dietetic Association (ADA diet) (n = 10). Seventy-two hours before beginning their diets and then 48 h, 1, 2, and 3 weeks after starting, participants completed a battery of cognitive tasks assessing visuospatial memory, vigilance attention, memory span, a food-related paired-associates a food Stroop, and the Profile of Moods Scale (POMS) to assess subjective mood. Results showed that during complete withdrawal of dietary carbohydrate, low-carbohydrate dieters performed worse on memory-based tasks than ADA dieters. These impairments were ameliorated after reintroduction of carbohydrates. Low-carbohydrate dieters reported less confusion (POMS) and responded faster during an attention vigilance task (CPT) than ADA dieters. Hunger ratings did not differ between the two diet conditions. The present data show memory impairments during low-carbohydrate diets at a point when available glycogen stores would be at their lowest. A commonly held explanation based on preoccupation with food would not account for these findings. The results also suggest better vigilance attention and reduced self-reported confusion while on the low-carbohydrate diet, although not tied to a specific time point during the diet. Taken together the results suggest that weight-loss diet regimens differentially impact cognitive behavior.

Also at ScienceDaily. Small N's. What were the N's on the Creatine studies???


Friday, November 21, 2008

Sex differences, ideology and IQ   posted by Razib @ 11/21/2008 09:08:00 AM

The Audacious Epigone has two interesting posts up right now. Conservative men more intelligent than conservative women; Liberal women more intelligent than liberal men and Politics and IQ; Conservative Democrats and liberal Republicans least intelligent. The titles are self-evident, but, I would add that with hindsight it might make sense that liberal Republicans aren't too bright. If you're a liberal Republican you are probably just in denial, or, confused and dull. When I think liberal Republican I think Tom Campbell or Chris Shays, but these may simply be elite examples who don't reflect the fact that most ideological outliers in parties are just individuals who don't think deeply. For example, someone who was born into a "Republican family," and doesn't reflect much about ideology and so continues to vote Republican despite being liberal. I don't feel I need to explain conservative Democrats, as it seems to me that political exemplars of this class are generally duller than liberal or moderate Democrats.

Note: I know this is kind of a political post, but I'm going to be strict about not letting the comment thread degenerate immediately. So don't get offended if I don't let you through the mod-queue even if I normally do.


Thursday, November 13, 2008

Why do intelligent people live longer?   posted by p-ter @ 11/13/2008 08:01:00 PM
Share/Bookmark the title of an interesting essay by Ian Deary in this week's Nature. The article is short and quite accessible, and well worth a read.


Monday, November 10, 2008

Smart people play nice   posted by Herrick @ 11/10/2008 10:35:00 PM

That's the result from a new experimental study of 1,000 people attending truck driving school. The authors tested all of them with Raven's Progressive Matrices, a real IQ test. They then put pairs of them through a prisoner's dilemma game, and found:
[M]easures of cognitive skill [CS] predict social awareness and choices in a sequential Prisoner's Dilemma game. Subjects with higher CS's more accurately forecast others' behavior....[S]ubjects with higher CS's also cooperate more as first movers.
This set of genuine experiments improves on this older paper, which found that students at high-SAT schools cooperated more in prisoner's dilemmas than students at low-SAT schools. Now we know it's not just because posh, high-SAT schools facilitate a "culture of cooperation" or something like that. Smart individuals just figure it out on their own.....

Bottom line: More evidence that smarter groups are more likely to think win-win.


Thursday, September 25, 2008

Brian Ferguson and Ashkenazi IQ   posted by Razib @ 9/25/2008 09:51:00 PM

It's up, How Jews Became Smart: Anti-"Natural History of Ashkenazi Intelligence" (big PDF). The long-awaited rebuttal to the Natural History of Ashkenazi Intelligence.

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Monday, September 22, 2008

College is Still the Best Pay-off   posted by Jason Malloy @ 9/22/2008 08:59:00 AM

Recently Charles Murray has promoted the idea that too many people are seeking 4 year degrees: "Let's stop this business of the B.A., this meaningless credential". Last year he wrote in the Wall Street Journal:

If you want to do well [in college], you should have an IQ of 115 or higher. Put another way, it makes sense for only about 15% of the population, 25% if one stretches it, to get a college education. And yet more than ... 40% of all persons in their late teens are trying to go to a four-year college--enough people to absorb everyone down through an IQ of 104.

Several months ago, the Inductivist found this to be a canny estimate: in the 1960s the average college graduate had an IQ very close to 115, and today the average college graduate has an IQ of 105.

But what does this mean for the individual? Murray suggests that college debt, lack of relevant job training, and years of lost workforce wages and experience await those below the 85th percentile:

They are in college to improve their chances of making a good living ... and would do better in vocational training ... two-year colleges ... [are] about right for learning many technical specialties, while four years is unnecessarily long ... Finding a good lawyer or physician is easy. Finding a good carpenter, painter, electrician, plumber, glazier, mason--the list goes on and on--is difficult, and it is a seller's market. Journeymen craftsmen routinely make incomes in the top half of the income distribution while master craftsmen can make six figures.

I find the thinking here plausible, and these seem like testable enough ideas. Luckily, all the relevant variables are included in the General Social Survey.

It's graph day on gnxp. The x axis in the figure below represents the number of correct answers on the 10 question WORDSUM mini IQ test included in the GSS. The y axis represents the respondent's income in constant dollars. The colored lines represent five educational categories, and one occupational category. Moving left to right we see the average income of people in each category as their IQ score increases from 0-10 correct answers. 'Junior college' represents the two-year vocational degree Murray references. And 'Craft and Trade Workers' covers over 50 skilled trade categories like electrician, mason, plumber, carpenter, and mechanic, coded by the survey.

The first observation here is that educational degrees, whether they confer skills or credentials, are more important to income than IQ when minimum thresholds are met. Trade workers, and 2 and 4-year college graduates are not significantly represented in the lowest three IQ categories. Graduate holders have an even higher minimum IQ. Second, income rises within 5 of the 6 categories as IQ increases. Higher IQ generates the biggest pay-off differences between those with advanced degrees, which is consistent with IQ increasing in importance as jobs become more complex. Third, merely earning a Bachelor's degree is a golden ticket. People with average and below average IQs are getting just as much of a financial return out of their 4-year degree as those above the 85th percentile. This suggests many more people of marginal ability should be seeking a Bachelor's degree, not less. Fourth, the two lines for junior college and trade occupations overlap substantially, as we would expect if most people in trade occupations went to trade school. Fifth, and most directly related to Murray's argument, people with 4-year degrees earn much more than people with 2-year degrees and trade jobs at every level of IQ. Average IQ people will get a much, much larger monetary reward from completing a 4 year school than a 2 year school. So the BA is far from being a "meaningless credential" when it comes to "chances of making a good living".

It's possible people with average IQs who complete college are exceptional in other ways. But there is no other empirical evidence that vocational school is better at generating income for those <85th percentile.

Also, secular trends could distort data in the first graph, which combines all survey data from 1972-2006. So the second graph below represents only people who were 35 and older and surveyed between 2000-2006. Fortunately, the results are not too different from the first graph. The IQ categories are condensed and transformed, and we see that 96 is about the minimum to complete 2 and 4 year college, and 111 the minimum for graduate degrees. Again we find that IQ shows no relationship to income for those with a BA, and, in fact, those with lower IQs might profit the most. For those without advanced degrees, people who are moderately above and moderately below average intelligence might earn the most (this balance might be because other socially valued personality traits, like masculinity, are inversely associated with IQ).

So, while I have yet to read Real Education -- which may address these issues -- it would appear that Murray is mistaken in some of his crucial premises.

Still undetermined is if people with 4 year degrees earn a lot more money because they actually acquire important skills, or if inefficient laws/taboos against employee IQ testing, sustain a comically messy and tragically expensive employment screening method. If the latter was true Murray could still be partially correct: 4 year college could be worthless for the <85th percentile, if employers began to use 20 minutes of psychometric testing, instead of 4 year degrees, as their screening filter.

But, ceteris paribus, college is still the best pay-off.

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Wednesday, September 10, 2008

Effects of Prenatal Cocaine Exposure on IQ   posted by ben g @ 9/10/2008 07:13:00 PM

In Obama's unexciting review of the Bell Curve, he remarked:

no one disputes that children whose mothers smoke crack when they're pregnant are going to have developmental problems.

The relevant studies reveal a more complex picture, though. The effects of prenatal cocaine exposure on IQ remain heavily contested to this day. However, recent evidence from Bennett et al points to a 3 to 5 IQ point drop, on average. This is the most recent study on this subject that I'm aware of.

Interestingly, in following with a few previous studies, it was found that boys suffer a greater cognitive loss from prenatal cocaine exposure than girls. Also, the study found that 9 year olds had equally fewer IQ points as their 4 year old counterparts, countering to a certain extent the idea that the IQ loss goes away as development progresses.

If Bennett's numbers are correct, they have small-- but significant-- implications for the Black-White IQ gap. Unlike tobacco and alcohol, which are used by pregnant white and black women at about equal rates and intensities on average*[1], black women are much more[2] likely than white women to use cocaine or crack while pregnant. This is relevant to behavioral genetic studies-- both past and present-- which have aimed to understand the relative contributions of genetics and environment to the IQ gaps. There is no way, as far as I know, to extract prenatal factors like cocaine use from measures of heritability without explicitly measuring such inputs. As far as adoption studies in particular, it stands to reason that women who place their babies up for adoption exceed the rest of the US population in pregnant cocaine use. An interesting thing about the Scarr adoption study is that all of the mothers of the half-black kids were white.

[1] Today, that is. 1989 was the earliest year I could find data for, and in that year the pattern is starkly different from today-- the black-white ratio in fetal alcohol syndrom for this year has way more alcohol use by pregnant black women than pregnant white women, and also much higher rates of fetal alcohol syndrome among black babies. I'm not sure if the rates were comparable in say the 70's, when the Scarr adoption study was performed. That would be interesting data if anyone happens to have it.

[2]~12 times more in the second link, from 1994

*Source for the alcohol/tobacco/fetal alcohol syndrome rates is the CDC.


Tuesday, September 09, 2008

Barack Obama on The Bell Curve   posted by Razib @ 9/09/2008 09:09:00 PM

Related: Wayne Allyn Root smarter that Barack Obama?.

Jason's comment deserves promotion so that Google picks it up:

October 28, 1994
SHOW: All Things Considered (NPR 4:30 pm ET)

Charles Murray's Political Expediency Denounced
SECTION: News; Domestic
LENGTH: 635 words

HIGHLIGHT: Commentator Barack Obama finds that Charles Murray, author of the controversial "The Bell Curve," demonstrates not scientific expertise but spurious political motivation in his conclusions about race and IQ.

BARACK OBAMA, Commentator: Charles Murray is inviting American down a dangerous path.

NOAH ADAMS, Host: Civil rights lawyer, Barack Obama.

Mr. OBAMA: The idea that inferior genes account for the problems of the poor in general, and blacks in particular, isn't new, of course. Racial supremacists have been using IQ tests to support their theories since the turn of the century. The arguments against such dubious science aren't new either. Scientists have repeatedly told us that genes don't vary much from one race to another, and psychologists have pointed out the role that language and other cultural barriers can play in depressing minority test scores, and no one disputes that children whose mothers smoke crack when they're pregnant are going to have developmental problems.

Now, it shouldn't take a genius to figure out that with early intervention such problems can be prevented. But Mr. Murray isn't interested in prevention. He's interested in pushing a very particular policy agenda, specifically, the elimination of affirmative action and welfare programs aimed at the poor. With one finger out to the political wind, Mr. Murray has apparently decided that white America is ready for a return to good old-fashioned racism so long as it's artfully packaged and can admit for exceptions like Colin Powell. It's easy to see the basis for Mr. Murray's calculations. After watching their income stagnate or decline over the past decade, the majority of Americans are in an ugly mood and deeply resent any advantages, realor perceived, that minorities may enjoy.

I happen to think Mr. Murray's wrong, not just in his estimation of black people, but in his estimation of the broader American public. But I do think Mr. Murray's right about the growing distance between the races. The violence and despair of the inner city are real. So's the problem of street crime. The longer we allow these problems to fester, the easier it becomes for white America to see all blacks as menacing and for black America to see all whites as racist. To close that gap, we're going to have to do more than denounce Mr. Murray's book. We're going to have to take concrete and deliberate action. For blacks, that means taking greater responsibility for the state of our own communities. Too many of us use white racism as an excuse for self-defeating behavior. Too many of our young people think education is a white thing and that the values of hard work and discipline andself-respect are somehow outdated.

That being said, it's time for all of us, and now I'm talking about the larger American community, to acknowledge that we've never even come close to providing equal opportunity to the majority of black children. Real opportunity would mean quality prenatal care for all women and well-funded and innovative public schools for all children. Real opportunity would mean a job at a living wage for everyone who was willing to work, jobs that can return some structure and dignity to people's lives and give inner-city children something more than a basketball rim to shoot for. In the short run, such ladders of opportunity are going to cost more, not less, than either welfare or affirmative action. But, in the long run, our investment should payoff handsomely. That we fail to make this investment is just plain stupid. It's not the result of an intellectual deficit. It's theresult of a moral deficit.

ADAMS: Barack Obama is a civil rights lawyer and writer. He lives in Chicago.


Friday, July 18, 2008

The Inheritance of Inequality: Big Insight, Small Error   posted by Herrick @ 7/18/2008 03:58:00 PM

Gintis and Bowles have done great work cleaning up a lot of the discussion about cooperation, evolution, and economic outcomes. A Google Scholaring of their names turns up 14 items with over 100 citations, most of which would be well worth reading for GNXP regulars.

But that said, in their 2002 Journal of Economic Perspectives piece "The Inheritance of Inequality," they appear to make a small error. It's an error that's all-too-easy for even good folks to make: They apparently squared the h-squared.

Their big insight and their small error are all part of answering a simple question: How much of the correlation of income between parent and child can be explained by the heritability of IQ? You might think it's straightforward: IQ is highly heritable, so if there's some channel linking IQ to income, then it's all over but the shouting.

But numbers matter. And Gintis/Bowles work out the numbers, finding that there's a weak link in that causal chain: The low correlation (0.27 according to Gintis and Bowles) between IQ and wages. The causal chain goes like this:

1. Parental earnings have a 0.27 correlation with parent's IQ.
2. Heritability of IQ between parent and child is a bit more than 1/2 of h-squared (why a bit more? assortive mating). They take an h-squared of 0.5 for IQ.
3. Child's earnings have a 0.27 correlation with child's IQ.

So the net result is 0.27*0.3*0.27 = 0.022 (page 10). A very small number, especially since the raw parent-child income correlation in U.S. data is about 0.4. So yes, knowing a parent's income helps you predict their adult (especially male) child's income. But only 5% (or 0.022/0.4) of the total correlation can be explained by IQ's impact on wages. Small potatoes.

(Oh, but where's the small error? It's where Gintis and Bowles report that the net result is 0.01 instead of 0.022--a difference that I can most easily attribute to a mistaken squaring of the h-squared.)

If I really wanted to get that net result up from a measly 5%--if I knew in my heart that IQ really was a driving force in intergenerational income inequality--then how would I do it? Well, I might use a higher heritability of IQ, I might assume more assortive mating, or I might assume a bigger correlation between wages and IQ.

Hard to do much to budge that IQ/wage link: Zax and Rees's paper only has a 0.3 correlation between teenage IQ and middle-aged wages, and when Cawley, Heckman et al. regress NLSY wages on the first 10 principal components of the AFQT, they get a similar result.

So you think maybe a higher heritability of IQ will save you? Well, let's just go all the way to perfect heritability of IQ and perfect assortive mating on IQ. In other words, let's see if "IQ clones" will be have enough similarity in wages to match the 0.4 intergenerational correlation of income.

Will the IQ clones have similar incomes? Not so much. (0.3^2)*1 still equals something small: 0.09. Less than 1/4 of the intergeneration correlation in income. Medium-sized potatoes, but we had to make a ton of ridiculous assumptions to get there.

It's that doggone low correlation between IQ and wages, a correlation that has to be squared because we're comparing parent to child. So a high heritability of IQ doesn't imply a high heritability of IQ-caused-income. Another reminder that lots of things impact your wages: Not just how smart you are.

Gintis and Bowles work through some finger exercises to argue for big environmental effects, and that's all well and good. But to my mind, the interesting fact is that income is still highly heritable!

G/B report that MZT (identical twin) earnings correlation is 0.56, and DZT (fraternal twin) earnings correlation is 0.36, so using the crudest of approximations, the heritability of earnings is still (0.56-0.36)*2=0.4. So income apparently has a modestly high heritability, but most of it can't be explained by the IQ-wage channel. Looks like the genetic heritability of income is being driven mostly by non-IQ channels.

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Tuesday, July 15, 2008

Regional differences in intelligence?   posted by Razib @ 7/15/2008 10:32:00 PM

In the post below, Colder climates favor civilization even among Whites alone, I made a few comments about possible differences between Germans in Illinois and Germans in Texas, based on nothing much more than a hunch. I trust my hunches, but there's no reason you should, so I decided to see if there was anything here in regards to my assumption about interregional differences in intelligence and how they might track across ethnic groups. So of course I went to the GSS website, and checked the mean WORDSUM scores of various white ethnic groups broken down by region. I specifically focused on whites who stated that their ancestors were from England & Wales, Germany and Ireland. My reasoning is that these are three groups with very large N's within the GSS sample and they are well represented across the regions in absolute numbers. My main motivation was see if the differences across regions were similar for all three groups. Here are the states for each region (the Census made up these categories):

New England - Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut
Middle Atlantic - New York, New Jersey, Pennsylvania
East North Central - Ohio, Indiana, Illinois, Michigan, Wisconsin
West North Central - Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas
South Atlantic - Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida
East South Central - Kentucky, Tennessee, Alabama, Mississippi
West South Central - Arkansas, Louisiana, Oklahoma, Texas
Mountain - Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada
Pacific - Washington, Imbler, California, Alaska, Hawaii

Obviously the breakdown isn't ideal. I think Delaware and Maryland arguably should be Mid-Atlantic. I also believe that Wisconsin is more plausibly in the West North Central than Missouri or Kansas is. But those are the regional breakdowns and I can't do anything about them.

So, WORDSUM is a vocabulary test on a 0-10 scale. For the whole GSS sample the mean was 6.00, with 1 standard deviation being 2.16. Below is a chart which shows the relationship between WORDSUM scores (Y axis) for various regions (X axis) for each of the three ethnic groups:

The tables below are pretty self-explanatory. At the top you see the mean WORDSUM scores for each ethnic group for each region. I put the N's in there as well so you can see that the sample sizes were pretty big. Note that there is more interregional variation within an ethnic group than there is interethnic variation within a region (the standard deviation across the columns is 50% bigger than across the rows). Just to be clear, I also included some tables which show the differences in WORDSUM mean scores between the regions like so: (row - column) = value.

New England

Middle Atlantic

East North Central

West North Central

South Atlantic

East South Central

West South Central




England & Wales

































England & Wales

New England

Middle Atlantic

East North Central

West North Central

South Atlantic

East South Central

West South Central



New England










Middle Atlantic










East North Central










West North Central










South Atlantic










East South Central










West South Central































New England

Middle Atlantic

East North Central

West North Central

South Atlantic

East South Central

West South Central



New England










Middle Atlantic










East North Central










West North Central










South Atlantic










East South Central










West South Central































New England

Middle Atlantic

East North Central

West North Central

South Atlantic

East South Central

West South Central



New England










Middle Atlantic










East North Central










West North Central










South Atlantic










East South Central










West South Central






























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Colder climates favor civilization even among Whites alone   posted by agnostic @ 7/15/2008 02:12:00 AM

Last year I had a crazy idea about how winged insects might influence civilization. I only pointed to winged insects as an exemplar, not to suggest a "Mosquito Theory of History" or something stupid and sexy like that. The reasoning is simple: insects are more likely to be winged in certain climates, and that means more effective vectors of disease in such environments; and a greater disease burden makes you dumber, more tired, and more irritable, which stunts the growth of civilization. [1] A qualitative follow-up post looked at where civilizations have ever appeared, and in what climate types they existed.

Well, now I've done some quantitative work, and it turns out that I was right. One critique against an international study is that natural selection may have adapted people to be more or less civilized in different environments, so that the only influence of climate is as a selection pressure for genetic change. There are at least two such studies already out there: one by Templer & Arikawa (2006) and another by Vanhanen (2004). I'm arguing that it matters even when people start out pretty much the same genetically, so I will look just at the US. It varies enough in climate and degree of civilization that any correlation should jump out.


In particular, I will look at the correlation, on the level of states, between average annual temperature and the average IQ of Whites, post-secondary degrees awarded to Whites per capita, and the percent of the White population that's imprisoned. I only look at Whites in order to avoid the confound of climate with racial composition (for example, the cold Mountain states are heavily White, while Blacks make up a larger fraction in the hot Southeast).

The reason I look at basic measures like IQ or being in jail, as opposed to the loftier things we associate with civilization, is that smarts is the key determinant of propelling the institutions of civilization forward, while crime gives us a good rough idea of how barbaric we are on a personal level. I'm sure that governments can improve or screw things up too, but it's the raw cognitive and behavioral materials that matter most, as Lynn and Varhanen show in IQ and the Wealth of Nations (see all GNXP posts on this topic). Moreover, studies of representative samples of the population always show a strong influence of IQ on how cultured a person is. See, for example, a National Endowment for the Arts report on the demographics of arts attendees (PDF p. 19), which shows that attendance increases nearly monotonically by education level.

The results

As you can see, hotter average temperature is associated with lower White IQs, fewer degrees being awarded to Whites per capita, and a higher percentage of the White population being imprisoned. The relationship looks pretty linear in each case, and the data are on an interval scale, so we check the Pearson correlation coefficient: between White IQ and temperature, it is -0.48 (p = 0.0005, two-tailed); between degrees to Whites and temperature, it is -0.57 (p = 0.00002, two-tailed); and between percent of Whites in jail and temperature, it is +.40 (p = 0.005, two-tailed). Even conservatively correcting for three independent hypotheses still leaves all results significant (and IQ and getting a college degree are not even independent). At any rate, average temperature accounts for 23%, 32%, and 16% of the variance in White IQ, degrees to Whites, and percent of Whites in jail, respectively -- pretty damn good for social science. [2]


I took the average annual temperature for each of the 48 continental states (Alaska and Hawaii were not included in the source, so I left them out). Next, I used Audacious Epigone's estimates of White IQ by state, which are based on NAEP data from 8th grade math and science test scores (read about his methods here). I turned to for the per capita number of post-secondary degrees awarded to Whites. For the number of Whites in prison per 100K Whites in the state's population, I used the data from 1997 in a study by the National Center on Institutions and Alternatives (PDF here), which separates non-Hispanic Whites from Hispanics, unlike most crime data from government agencies. [3]


Here, correlation probably is causation, as climate precedes the other three variables in causality, and again because these are unlikely to be genetic differences that reflect adaptation to different environments -- one of the few cases where natural selection "has not had enough time."

An objection is that the differences could reflect a "brain drain," whereby smart people flock to colder states, and their smart children boost the state's NAEP scores. Even in this case, where climate does not cause group differences in IQ, it still confirms the hypothesis that colder climates favor civilization -- why else would smarties flock there? But I doubt this anyway, since Montana, Wyoming, and North and South Dakota are not exactly fonts of civilization that smarties pour into, yet they have White IQs on par with the highly developed New York City metro area.

If it is causation, as seems likely, the mechanism could be anything. Pathogen load is surely part of it, hence the fields of study called "tropical disease" and "tropical medicine." Also, you might sweat too much in hotter environments, bringing you closer to dehydration. As mild as these effects may seem, when accumulated over the course of development, they could result in your body spending more resources on bodily maintenance than on luxury items like IQ and toil. Heat could also just make you more fatigued -- that wouldn't affect IQ, but it would affect your work ethic, making you less likely to complete college and more likely to pursue quick fixes like crime to get what you want.

The correlation is stronger for getting a college degree than performance on 8th grade math and science tests, and that could be because college work is more g-loaded, because it also taps into work ethic aside from IQ, and because out-of-staters show up in the college figures but not the 8th grade figures. As tough as the environment may seem to natives, it must seem unbearable to college students raised in a different climate.

To the best of my knowledge, as the saying goes, this is the first demonstration of an association between climate type and IQ, civilization-related achievement, and crime, even among a population that's pretty homogenous genetically (for the traits of interest, at least). Even what genetic diversity there is among Whites would underestimate the effect -- Whites adapted to hotter environments, such as Italians and Greeks, are far more concentrated in the colder states within the US. To put the final nail in the coffin, though, you'd want to look at babies of Whites who are adopted into White families in a state of noticeably different temperature than that of the biological parents.

Still, it seems pretty unavoidable: hotter environments are less conducive to civilization, at least for Whites, and not just in extreme cases like the failed attempt to colonize sub-Saharan Africa. Civilization may have started in hot areas, but that was then. It apparently flourishes much more in colder climates. Just as we provide iodine in table salt to prevent a nutrient deficiency from lowering IQ, it might be just as well to encourage people to settle colder areas.

It's not like they'd be abandoning civilization -- just the opposite. They could take their accents, music, and whatever else with them, but they would not suffer the environmental insults that lower their group's IQ, lower their ability to get a college degree, and make them more likely to commit crime. Fortunately for them -- and unfortunately for current residents -- the Mountain states have incredibly low population densities and could absorb some Whites from hotter states. That would certainly burden the locals for a generation, but again since lower White IQ in the Southeast is probably due to largely treatable environmental causes, it won't take long for them to contribute as citizens on the same level as the locals.


[1] Underlying this is likely a tendency for all sorts of things to be more migratory in such environments -- winged insects were chosen because there's lots of solid data to illustrate the point. Basically, environments that are highly unstable favor migratory features since your environment may go from good to bad from one day to the next, or from one spot to the next -- and being able to quickly move on to greener pastures will be well worth it. When environmental quality does not change much in space or time, then the expensive wings (or whatever) will not pay off.

[2] If you don't have statistical software, you can do a lot for free on, including correlation.

[3] Although I didn't run a test of normality on the distributions for temperature, iq, degrees, or crime, I did check the skewness of all, and only crime was significantly skewed: for crime, skewness is +2.1 standard errors of skewness (SES); for temperature, +1.24 SES; for degrees, +0.35 SES; and for IQ, -1.51 SES.

Addendum from Razib: I put up a related post at my other weblog.

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Wednesday, June 18, 2008

East Asian psychometric variance   posted by Razib @ 6/18/2008 11:42:00 AM

Asian-White IQ variance from PISA results:
The NE Asians performed about .5 SD better on average (consistent with IQ test results), and exhibited similar (slightly higher) variance.

Interestingly, the Finns performed quite well on the exam, posting a very high average, but their SD is slightly smaller. The usual arguments about a (slightly) "narrow bell curve" might apply to the Finns, but apparently not to the NE Asians.

Read the whole post to see if you follow the logic of the inferences; I've done some digging on this before to spot check the Europeans-higher-variance meme and didn't find much to support it, and some data to disprove it (though you could explain away that data because of clumping of distinct populations, etc.). That's the main reason I get irritable whenever this meme pops up in the comments, it's one of those "facts" which exhibits circular citation dynamics and spreads like wildfire. Of course, it isn't as if the meme is totally emerging out of a vacuum: if East Asians are so smart why aren't they as scientifically creative??? It seems to me that the most plausible explanation has to be that individual intelligence isn't sufficient for intellectual creativity, though it is likely a necessary precondition. Some of the other variables might be rooted in individual psychology (personality), but I suspect others manifest on a larger scale (e.g., the top-down paternalism and emphasis on conformity which is the norm in most East Asia societies).

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Sunday, June 08, 2008

IQ and Higher Education   posted by DavidB @ 6/08/2008 04:25:00 AM

Readers in the UK may have seen recent press reports about a controversial article by Bruce Charlton, an evolutionary psychologist at the University of Newcastle. Charlton points out that average IQ differs in different social or occupational classes (e.g. doctors or lawyers have higher IQ than casual labourers), and that in consequence, if IQ is relevant to higher education, we would expect participation in higher education also to vary according to class. Predictably, ritual curses and denunciations have rained down on Charlton's head.

I wanted to read Charlton's article, but found it more difficult to find than I expected. The press reports suggested that it appeared in Times Higher Education (the former Times Higher Educational Supplement), but on tracking down the relevant issue I found a report about Charlton's article, but not the article itself. The article is however available as a Word document on the THE website. (See the right margin of the webpage here). I make a few comments of my own below the fold.

Probably most readers will agree with the broad thrust of Charlton's article, but there may be a confusion between the IQ of parents and that of their offspring. Charlton seems (as far as I can see) to assume that the mean IQ of applicants to higher education is the same as that of adults in their parental social class. This is not generally the case. The correlation between the IQ of parents and offspring is only about .5, which implies considerable regression towards the mean. The IQ of the offspring of parents with IQ of, say, 130 will on average be lower than 130, while that of parents with IQ of, say, 85 will be higher than 85. There is a difference of up to 40 IQ points between adults in the highest and lowest occupational classes (depending on the classification used), but only about 15 to 20 points between children from those classes. (For some data see Anastasi, chapter 15.) The difference in average IQ between social classes is kept roughly constant by social mobility, as the dimmer children of the higher classes tend to fall in the social scale and the brighter children of the lower classes tend to rise. (See Mackintosh, pp. 144-8). This does not invalidate the main point of Charlton's article, but it may affect some of his specific quantitative comparisons.

I think it may also be unfortunate that Charlton describes the present system of entry to higher education as 'meritocratic'. Entry to publicly funded higher education should not be seen (primarily) as a reward for past achievement, or a badge of 'merit'. The proper criterion for entry decisions is how far an individual can benefit from the course of study concerned. In general, individuals who have struggled at school are unlikely to benefit from higher education at all. If applications for a particular course of study exceed the number of places available, those applicants should be chosen who will benefit most from the use of scarce resources. It is the scarcity of high quality resources that justifies the selectivity of the 'elite' universities. One would not expect an haute couture seamstress to stitch potato sacks, and one should not expect a Fellow of Trinity College Cambridge to teach mediocre students. Such students would not derive the greatest benefit from the teaching, and indeed the teaching would probably not be the best available for such students.

I am assuming in all this that higher education is by definition at a more advanced and demanding level than that of ordinary school education. It is not to be confused with post-school education at a similar level to that of schools, such as is provided by Further Education Colleges in Britain. This may be admirable in its own way, but it is not higher education.

Anne Anastasi: Differential Psychology, 3rd edn., 1958
N. J. Mackintosh: IQ and Human Intelligence, 1998

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Wednesday, May 14, 2008

IL1RAPL1 and human cognitive ability   posted by Razib @ 5/14/2008 10:06:00 PM

A study on the correlation between IL1RAPL1 and human cognitive ability:
This study aimed to investigate the effects of IL1RAPL1 on the human cognitive ability...Results indicated that genotypes of DXS1218, DXS9896 and rs12847959 were associated with memory/concentration factor intelligence quotient (IQ)...DXS1218 also associated with full IQ, verbal IQ, and performance IQ...rs12847959 were related to verbal comprehension factor and perceptual organization factor IQ...Further study on rat brain revealed that Il1rapl was mainly expressed in memory/concentration-associated encephalic regions, such as hippocampus, dentate fascia, osmesis perithelium, and piriform cortex. mRNA expression levels of Il1rapl in brains of rats with different learning and memory abilities showed significant difference. Combined data suggested that IL1RAPL1 affected human cognitive ability to some extent, especially the memory and concentration capability.

Check out the HapMap on that SNP. Remember to wait up on reproducibility here. Sandy has a longer post addressing the radioactivity of such research (obviously he is lying when he says he's an anthropologist; doesn't pass the smell test).

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Tuesday, April 01, 2008

Massive QTL for IQ discovered....   posted by Razib @ 4/01/2008 12:06:00 AM

Just got a note from someone I trust that a massive QTL for IQ has been discovered, on the order of 10 points in effect for a substitution of the the major allele for the minor (it's additive and independent, so homozygote minor allele ~ 20 points greater than homozygote major allele). The novel variant is found in an ethnic-religious minority population and no other phenotypic effects are discernble for those who carry the IQ boosting polymorphism. Everything is very preliminary at this point...but they've checked and re-checked and this seems to be real. There are two genes previous implicated in neurological pathologies in this region of the genome, so a molecular genetic & physiological story should be easy to extract.

I'm being a little vague on the details for obvious reasons; no one wants to be scooped. But word is spreading through the labs though, so my friend thought it might be good to prep the public and those at GNXP who are interested in this topic. Expect a Nick Wade article as soon as possible. Exciting times....

Update: Yes, April Fool's. Obviously I wasn't going to do something like taking down the site and pretending someone was going to sue us; you might recall that several GNXP readers sent the befuddled sysop of the Gene Expression Omnibus some irate emails....

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Tuesday, November 27, 2007

Jim Manzi on IQ differences   posted by Razib @ 11/27/2007 10:07:00 PM

Over at The American Scene Jim Manzi has an interesting post.


Sunday, November 25, 2007

Linguist: I can use R, you can't. Thus, your motives are questionable. QED.   posted by p-ter @ 11/25/2007 09:18:00 AM

Mark Liberman at Language Log (a blog which I very much enjoy, I should point out) approvingly links to Cosma Shalizi's rant against Slate for publishing a series of articles on race and IQ. His conclusion:
So to start with, you should ask yourself whether you can define and calculate the variance of a set of numbers, or the correlation between two sequenccs of numbers. If not, then read the (linked) wikipedia articles -- and spend a little time playing with the concepts in the context of an interactive program like R. Once you've paid that entry fee, read Cosma's posts. (It's more fun that you might think -- I especially recommend the discussion of the heritability of zip codes, and you could go back and read the prequel about the heritability of accent.) And then go through William Saletan's articles, and decide for yourself what they mean about the abilities and motivations of the writer and his editors.
It's amazing how quickly people go from simple disagreement to armchair psychologist mode; a little perspective is in order here.

Dr. Liberman assumes that Cosma concludes that heritability estimates are worthless. This is not the case. Cosma points out that estimating heritability involves making assumptions that are often incorrect, but (I feel like I've said this many times before) all models are wrong, but some are useful. And buried in his prose (which contains many important, ill-understood points about the estimation of heritability), he cites a nice paper on the heritability of IQ, which concludes for a narrow-sense heritability of ~0.34 (that is, additive genetic factors account for ~34% of the variance in IQ, see the linked post). Cosma wants to add additional parameters to this model before he makes any definitive statements, but he can't bring himself to treat IQ differently than other traits:
If you put a gun to my head and asked me to guess [whether there are genetic variants that contribute to IQ], and I couldn't tell what answer you wanted to hear, I'd say that my suspicion is that there are, mostly on the strength of analogy to other areas of biology where we know much more. I would then - cautiously, because you have a gun to my head - suggest that you read, say, Dobzhansky on the distinction between "human equality" and "genetic identity", and ask why it is so important to you that IQ be heritable and unchangeable.
So if he had to guess, there is probably a genetic component to IQ, environment also plays a role, and human equality is not dependent on genetic identity. Seriously, read Saletan's column--these are exactly his points!

Referring back to my point about the utility of incorrect models, it's worth noting that, if you don't accept any of the heritability estimates proposed in humans, you're rejecting that any trait could be determined to have a genetic component before, oh, 2001. I don't think that's a good idea, and here's why: the heritability of type II diabetes was estimated at a "mere" 0.25 (using all those horribly flawed methods, and including, since it is a dichotomous trait, even more assumptions); now molecular studies have identified at least 9 loci involved in the disease. The heritability of Type I diabetes was estimated at about 0.88; now, there are 10 loci undoubtably associated with the disease. There are other examples, and more sure to come, but suffice it to say that heritability studies, with all their seemingly ridiculous assumptions, are not worthless.

Now look to Cosma's post on g. Again, this time in the footnotes, we see something in line with Saletan's article. Referring to the observation by economist Tyler Cowen that some people he knew in a village in Mexico were smart in ways not measureable by IQ tests, he writes:
Cowen points out behaviors which call for intelligence, in the ordinary meaning of the word, and that these intelligent people would score badly on IQ tests. A reasonable counter-argument would be something like: "It's true that 'intelligence', in the ordinary sense, is a very broad and imprecise concept, and it's not surprising the tests don't capture it perfectly. But the aspects of 'intelligence' they do capture are ones which are vastly more important for economic development than the ones displayed by Cowen's friends in San Agustin Oapan, however amiable or even admirable those traits might be in their own right." This would be a position about which one could have a rational argument. (Indeed, I might even agree with that statement, as far as it goes, as might A. R. Luria.)
So Cosma "might" agree that intelligence, as operationally defined by psychologists, is important for economic development and differs in distribution between groups. Interesting.

Cosma's posts seem to follow any discussion of IQ around in the "blogosphere". They're well-written, include legitimate discussion of many important issues in quantitative genetics and IQ testing (ok, I don't know much about IQ testing, but I'm assured this is the case by people who do), and come from an authority. But for whatever reason (I'm tempted to think that people don't actually read what he writes. I mean, it has, like, math and stuff), he's interpreted as saying that intelligence tests and the concept of heritability are entirely meaningless. That is not the case.

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Saturday, November 17, 2007

Questioning the breastfeeding-IQ-FADS2 connection, again   posted by p-ter @ 11/17/2007 08:21:00 AM

Razib noted, in his post on the IQ-breastfeeding-FADS2 story, that it reminded him of research on MAOA. There's a reason: it's by the same group. In fact, the IQ study is the third in a "trifecta" of gene-environment interactions postulated by Avshalom Caspi and colleagues. Curious about whether their statistical methods were similar in all these studies, I went back to them.

1. In 2002, the authors reported an interaction between variation in MAOA and childhood maltreatment on the probability of developing "antisocial problems". The relevant graph is on the right. It's important to keep in mind, from a statistical standpoint, what an interaction is: in a regression of variable Y on variable X, if the slope of the line significantly differs depending on another variable Z, one concludes for an interaction between Z and X. In this, the slopes do appear to be different, and the authors find this is indeed statistically supported. They don't include parental "antisocial behavior" as a covariate in their regression, either because they don't have that data or didn't think to include it.

2. In 2003, the authors then genotyped another locus in the cohort studied above, this time the serotonin transporter. They reported a significant interaction between polymorphism in this gene and stressful life events on risk of depression. Again the relevant graphs are on the right. Across several measures of depression, there does appear to be an interaction. Again, no inclusion of parental phenotype in the regression.

3. Now let's consider the IQ-FADS2 story. Again, they use the same cohort (as well as a replication cohort). This time, instead of genotyping known functional variants in a gene thought to be involved in the phenotype, they genotype a couple tagging SNPs in a gene picked through some spectacular logical leaps (1. there is a link between breastfeeding and IQ. 2. That link is modulted through fatty acid metabolism. 3. Of all the genes involved in fatty acid metabolism, the one of interest is FADS2). This has to change your priors on whether anything they find is real. Again, check the graph on the right: this time, they don't have the nice dose-response curve that they had in the others, so they go for a bar chart. And it does indeed look a little noiser. The replication, though, is something that wasn't present in the other studies.

The fact that they have a measure of maternal IQ but don't directly include it in the published multiple regression suggests that they tried it, but didn't like the results. They didn't include parental phenotype in any of their previous studies, but there, at least, there was some functional evidence linking the polymorphism and the phenotype. Here, there's nothing. Considering the fact mentioned in a previous post that other researchers find absolutely no evidence for link between IQ and breastfeeding (the entire basis for this study), this has to be classified as highly questionable. And regardless of the veracity of any gene-environment interactions here, the huge effects of breastfeeding on IQ shown by the authors are clearly artefacts of the heritability of IQ, and it's unfortunate that they are being propogated.

Half Sigma is apoplectic about this; I'm not so much-- this is a case of researchers having a hammer (their cohort and a desire to find gene-environment interactions), and seeing every problem as a nail, not some ode to breast-feeding.

Anyways, on a completely unrelated note, here's small nugget from their Supplementary Table 2, where they break down IQ by social class. I suppose I'd seen figures like this before (ie. in The Bell Curve), but it still gave me a start:

Low class: 93.5 (11.6)
Middle class: 100.5 (13.7)
High class: 111.4 (12.8)

In parentheses are standard deviations.

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Monday, November 12, 2007

Breast-feeding and IQ   posted by p-ter @ 11/12/2007 09:22:00 PM

In an interesting story on the relationship between teen delinquency and sex (long story short: people who concluded early sex caused delinquency unsurprisingly failed to control for genetics and were led astray) I saw this little bit:
A recent study by Scottish researchers asked whether the higher IQs seen in breast-fed children are the result of the breast milk they got or some other factor. By comparing the IQs of sibling pairs in which one was breast-fed and the other not, it found that breast milk is irrelevant to IQ and that the mother's IQ explains both the decision to breast-feed and her children's IQ.
Now, this is interesting in light of the recent study claiming to find a gene-environment interaction between breast-feeding and a particular gene. The source for the claim that breast-feeding has no effect on IQ is here. I went back and looked at the recent paper's attempts at controlling for maternal IQ. Statstically, this is not a difficult thing to do-- a linear regression of child IQ on maternal IQ, breast feeding status and genotype can easily be compared with a model that includes a breast feeding staus X genotype interaction.

The authors don't do this standard analysis, however--they only include a cryptic note explaining that there is no significant "interaction" between the SNP in question and maternal IQ. It's not the interaction term that's interesting, of course; it's whether the marginal effect of maternal IQ removes their already tenuous claims of an interaction between breast feeding and genotype. One gets the distinct feeling that some unfavorable results are being swept under the rug. Combine this, plus the study above, then add your prior probability that by genotyping two (2!) SNPs in the entire genome you'll find a real gene-environment interaction, and, well, it's not a stretch to say the authors haven't quite demonstrated what they think they have.

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Monday, November 05, 2007

IQ @ CATO Unbound   posted by Razib @ 11/05/2007 10:41:00 PM

The current issue of CATO Unbound is about IQ. James Flynn has already put something up, Linda Gottfredson, Stephen Ceci and Eric Turkheimer on deck.

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Breastfeeding & IQ & norm of reaction   posted by Razib @ 11/05/2007 06:07:00 PM

Read it here.

Update: Eye on DNA has much more.

Jason M. adds: In the comments HapMap Jockey Marc again applies the wisdom from p-ter's HapMap How-2 to the latest IQ genes:
In the study itself, there were two cohorts: a British cohort and a New Zealand cohort. In both cohorts, presence of the C allele (as either CC or CG) was associated with a hike in IQ by 6.4 and 7.0 points (from around 99-100 to around 106) in the two samples. But those without the C allele (GG) had mean IQs of 99.5 in Britain and 100.3 in New Zealand.

Incidentally, I plugged rs174575 into the ol' Hapmap, and it seems that the C allele has a frequency rate of 72% among Utah whites, 73% among Yorubans, 89% among the Chinese, and 90% among the Japanese.

Assuming these numbers are representative, universal breastfeeding alone would lead to a gap of 1.12 to 1.225 in IQs between East Asians and whites, favoring East Asians.

On the other hand, since whites and blacks have nearly the same C allele frequency (assuming, again that these numbers are representative of white and black populations), but whites breastfeed their babies at higher rates than blacks (60% vs. 30%, according to Steve), this is pretty solid evidence that increasing the percentage of black women who breastfeed their children will have a diminishing effect on the black white IQ gap.

Since I'm already blowing off work (damn you, Gene Expression!) I might as well do the calculations. Let's see... The 30% difference in breastfeeding is responsible for between 1.4 and 1.53 points in the black-white IQ gap! (I got these figures by multiplying the frequency rate of the C allele in Yorubans with the percentage difference in breastfeeding between blacks and whites with the effects of breastfeeding on the IQs of C allele carriers.)

Steve Sailer is vindicated!

Additional props to Rob in the comments at FuturePundit.

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Thursday, September 27, 2007

Cosma on IQ & heritability   posted by Razib @ 9/27/2007 09:20:00 PM

Cosma Shalizi has put up a gigantic post on IQ & heritability; he originally titled it "Duet for Leo and Razib," implying that I, and the audience here @ Gene Expression, are the targets of his eloquence (at least in part). Now, I have to admit something, I'm not really interested in psychometrics that much anymore. It has been a while since I have been, stupid people are obviously stupid and I am not interesting in debating that fact. I take my own opinions in this area as background assumptions, so I'm not going to respond to Cosma. In fact, I won't read the post right now, there's some interesting stuff on HLA & heterozygosity that I want to check out! But, I do invite readers to digest what Cosma is saying, because I guarantee you that you'll see it replicated by lesser minds elsewhere.

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Saturday, September 22, 2007

Heterosis and the Flynn Effect   posted by DavidB @ 9/22/2007 06:21:00 AM

I posted recently on the Flynn Effect, and some interesting papers on the subject came to my attention afterwards.

First, there is a review of Flynn's recent book by Richard Lynn in Intelligence, 2007, (35), 515-16. Lynn defends his own nutritional explanation of the Flynn Effect against various criticisms. He points out that it is one of the few theories that can explain an increase in IQ among young children.

A more substantial piece was mentioned in comments on my post. For several years M. Mingroni has been arguing that heterosis ('hybrid vigor') has played a major part in the Flynn Effect. This makes him unusual in proposing a mainly genetic, rather than environmental, explanation. His latest paper is in Psychological Review, 2007, 114(3), 806-29. An abstract is available here.

The first part of the paper criticises existing explanations such as nutrition, schooling, etc. Mingroni makes some good points, but I think that he and some others make the mistake of assuming that there has to be a single, or at least a main, explanation of the Flynn Effect. If the Flynn Effect were substantially uniform across all tests, all age groups, all countries, etc, this would be a reasonable assumption, but it isn't that uniform. There is no more reason to expect to find a single explanation of rising IQ scores than of rising life expectancy. The Flynn Effect might be due to a bit of nutrition, a bit of schooling, a bit of heterosis, a bit of audiovisual stimulation, and other factors, in various proportions in different times, places, and age groups. I'm all in favour of simple explanations where they work, but we should not always expect them to.

[Added on 24 September: Of course, all the various suggested factors - nutrition, schooling, heterosis, etc - are ultimately due to economic growth, but it would not be helpful to identify 'economic growth' as the 'cause' of the Flynn Effect, any more than of increasing life expectancy. We want something more specific. ]

The second part of Mingroni's paper is more constructive, and sets out a model for examining the effects of heterosis. I discuss it further below the fold, but I should stress now that Mingroni does not prove (or even claim to prove) that heterosis accounts for a large part of the Flynn Effect. Using plausible parameters his model only accounts for an increase of 2 to 5 points in mean IQ, which is less than a quarter of the cumulative Flynn Effect.

The possibility of heterosis increasing IQ scores is not controversial. Close inbreeding (e.g. cousin marriage) usually reduces the IQ of the offspring. This suggests that some genes for low IQ are recessive. Conversely, genes for higher IQ are probably often dominant. If so, then for any given set of underlying gene frequencies in the population, the mean IQ will be higher when the proportion of heterozygotes is higher. Random mating will therefore produce higher mean IQ than inbreeding, which for this purpose includes not only inbreeding in the traditional sense, but also breeding confined within subpopulations. If gene frequencies within such subpopulations vary, then the proportion of homozygotes will on average be higher than if the subpopulations were merged together in a random-mating total population.

If subpopulations are geographically or otherwise isolated from each other, they will evolve differing gene frequencies as a result of genetic drift or differential selective pressures. Over the last few centuries the population structure in many countries has changed in such a way as to break down such isolation. Small communities have been absorbed into larger towns, much of the rural population has migrated into cities, and improved transport has mixed up populations within the same countries and even internationally.

It is therefore reasonable to hypothesise that heterosis has made some contribution to the Flynn Effect. The question is how much. Mingroni's paper develops a model to explore this question. I can only give a rough outline here. It is assumed that a large number of loci affect IQ, with two alleles at each locus. The population is assumed to be initially subdivided and then merged into a single random-mating population. The variable quantities are the number of loci, the degree of dominance, the frequency of each allele in the total population, and the amount of increase in heterozygosity assumed to take place as a result of changing population structure. Values are assigned to genotypes in accordance with the degree of dominance, and gene frequencies for each allele are assigned stochastically to each locus within the subpopulations. The initial mean and standard deviation of IQ in the population resulting from the model is calculated and scaled to have a mean of 100 and s.d. of 15. The effect of the postulated change in heterozygosity on the mean and s.d. of IQ is then derived for a range of values for the key variables.

The choice of values is determined in part by plausibility and in part by empirical data. It is assumed that the number of relevant loci is either 50, 75 or 100. The dominant homozygote has the value 1, the recessive homozygote has the value 0, and the heterozygote has the value .6, .8 or 1 according to the degree of dominance. The population frequency of the recessive allele at each locus is either .4, .5, or .6. The increase in heterozygosity resulting from merging the subpopulations is either .02, .03, or .04; that is, between 2 and 4 percent. (These figures are based largely on Cavalli-Sforza's classic studies on isolated Italian villages in the late 1950s.)

With these assumptions Mingroni obtains increases in mean IQ ranging between 1.2 and 5.1 IQ points, with most results falling between 2 and 4 points. These changes are much smaller than the observed cumulative Flynn Effect, but Mingroni argues that the total change in heterozygosity at a national level might be much larger than those suggested by the Italian data. Opinions will differ on the plausibility of this. Personally, I would be sceptical. Cavalli-Sforza chose his Italian villages to represent a relatively isolated pattern of settlement and marriage, in order to give genetic drift a chance to show itself. I doubt that the traditional degree of isolation would be as large as this in many parts of Europe. (The degree of inbreeding might be higher in some non-European societies, especially where cousin-marriage is common.)

It is possible to calculate the initial difference in allele frequencies needed to produce a given increase in heterozygosity when the subpopulations are merged. For two equal subpopulations, and two alleles at a locus, the increase in heterozygosity produced by merging the subpopulations, as a percentage of the population, is (D^2)/2, where D is the difference in allele frequencies between the subpopulations. [Note] To produce an increase greater than Mingroni's upper figure of 4 percent the differences between subpopulations have to be quite large, e.g. a difference of around 30 percent in allele frequencies. This is larger than the usual differences between European nations, let alone different parts of the same nation. If there are more than two alleles the differences in allele frequencies have to be even larger. For example, if the subpopulations have 3 alleles at a locus, with frequencies of .2, .4, .4 in one subpopulation, and .1, .6, and .3 in the other (an aggregate difference of 40 percent), the effect of merging the subpopulations would only be to increase heterozygosity at the locus from .59 to .605. (If there are more than two subpopulations, a multi-allele system would have more scope, as each allele might be concentrated in a different subpopulation, but the differences in frequency between subpopulations would still have to be large to make much impact.)

In Mingroni's simulations an increase of 1 percent in heterozygosity produces an increase of about 1.1 points in the mean IQ of the population. The increase seems to be linear, as it should be, since each substitution of heterozygotes for homozygotes adds a fixed amount to the total IQ 'score' of the population. A cumulative IQ increase of around 20 points therefore requires an increase in heterozygosity equivalent to around 18 percent of the population. This requires a huge initial difference in allele frequencies - around 60 percent - larger than the usual difference between continents.

I also see a problem with the timing of the changes. In the first countries to industrialise, much of the breakdown in traditional population structure occurred in the 18th and 19th centuries. To take the most obvious example, in Britain some 90% of the population already lived in large towns and cities by the end of the 19th century. The scope for further increases in heterozygosity during the 20th century (excluding interracial mating) must have been quite small. Yet the Flynn Effect has been much the same in Britain as elsewhere.

Then there are those populations founded by immigrants. The best example is perhaps Australia. From the beginning of white settlement around 1800, the population of Australia was drawn from all over the British Isles (and contrary to myth, only a small proportion were convicts). If Mingroni is right in believing that heterosis can account for the bulk of the Flynn Effect, we would expect Australia to have had a spectacular one-off increase in IQ compared with the parent population. I mean no disrespect to Australia if I say that this has not been observed. Much the same argument can be applied to New Zealand and Anglophone Canada. The United States is a more complex case, as settlement extended over a longer period, and involved a variety of European groups who settled to some extent in different areas (Germans in Pennsylvania, Scandinavians in Minnesota, etc.) There could be parts of the United States where populations were quite inbred and the scope for heterosis was correspondingly large. But there must also have been areas (e.g. California and other west coast states) where the white population was well-mixed from the beginning of settlement. This would leave little scope for further IQ gains from heterosis. These are fairly obvious difficulties, but I cannot see that Mingroni addresses them

Note: Suppose the frequency of one allele in the total population is M. The frequency of the other allele is therefore (1 - M). Under random mating in the total population the proportion of heterozygotes will be 1 - M^2 - (1 - M)^2 = 2(M - M^2). Now suppose the population is divided into two equal subpopulations, A and B. If the frequency of one allele in A is (M - d), the frequency of the other allele must be (1 - M + d), while the corresponding frequencies in B are (M + d) and (1 - M - d). Under random mating within each subpopulation the average proportion of heterozygotes will be [1 - (M - d)^2 - (1 - M + d)^2 + 1 - (M + d)^2 - (1 - M -d)^2]/2 = 2(M - M^2 - d^2). This is 2d^2 less than under random mating in the total population. The amount 'd' is here the difference between the frequencies of each allele in the subpopulations and the mean for the total population. The difference in frequency of the same allele between the two subpopulations is 2d. If we set D = 2d, then 2d^2 = (D^2)/2. So it is easy to calculate the increase of heterozygosity (measured as a proportion of the population) resulting from the merger of the subpopulations for a given difference in allele frequencies, and the associated increase of IQ e.g.:

D...........(D^2)/2..........IQ points gain

These figures are independent of the value of M, but there are constraints on the possible values of D. E.g. if M is .8, D cannot be greater than .4, since M + D/2 cannot be greater than 1. There are of course many simplifying assumptions, so the figures should not be taken too seriously.


Friday, September 14, 2007

The Progression of IQ - a response to David Brooks   posted by Alex B. @ 9/14/2007 09:18:00 PM

In his September 14, 2007 op-ed piece in the New York Times, David Brooks tells his impression of the latest research in cognitive ability. Unfortunately, he not only misses the forest, but he bungles a few trees as well. Article and comments below.

A nice phenomenon of the past few years is the diminishing influence of I.Q.

Right out of the block he is off. In what domain was there once a non-zero IQ-outcome relation, but now, X number of years later, the relation has shown a systematic decrease? From the generality of the statement, one would expect this to hold across most, if not all, pertinent domains (e.g., occupation, academic success, etc.). However, that is not the case. Not only do the IQ-achievement, and IQ-occupation relationships still hold, but now there is a burgeoning new field in the area: cognitive epidemiology, that looks to see how health outcomes are related to cognitive ability. Deary et al give a terse summary here, and Gottfredson gives a conceptual overview here. But, perhaps more interesting, researchers who have no interest in intelligence per se are finding similar results: a case-in-point is Yakov Stern's cognitive reserve research that shows people with higher IQ scores tend to have have less severe symptoms of Alzheimer's symptoms. As this is a new area of inquiry, the exact nature of the relationship has not been identified, but one thing we can say for sure is that there is no diminishing influence of cognitive ability.

For a time, I.Q. was the most reliable method we had to capture mental aptitude. People had the impression that we are born with these information-processing engines in our heads and that smart people have more horsepower than dumb people.

These two statements have little to do with each other. IQ (at least as derived from a Full Scale score) has been, and still is, very reliable for most age groups and subpopulations, no matter how you measure reliability. For example, the Woodcock-Johnson, one of the more theoretically sound measures of cognitive ability, reports in their new normative update that the coefficient alpha values (which are a lower bound of reliability) above .90 for all ages ranging from 3 to over 80. Given that the maximum value alpha can take is 1 (under almost all circumstances), this is pretty good evidence. If you look at the technical manual for the Wechsler, Stanford-Binet, or Reynolds Intellectual Assessment Scales, you'll find very similar values (I refer to these only because their norms span a very large age group, and the full scale score is derived from multiple subtests). I challenge Mr. Brooks to find a more reliably-measured psychological construct in psychology, nay, in the social sciences.

The second statement, while perhaps overstated, is true. People are born with brains, these brains process information, and smarter people (as measured by IQ scores) tend to process information faster (see, for example, here and here). What impression should people have instead? People are born with a blank slate and all of life is little more that the acquisition of stimulus-response patterns? Skinner died in the 1990s, and strict adherence to this view died long before that (a great book about this).

And in fact, there's something to that. There is such a thing as general intelligence; people who are good at one mental skill tend to be good at others. This intelligence is partly hereditary. A meta-analysis by Bernie Devlin of the University of Pittsburgh found that genes account for about 48 percent of the differences in I.Q. scores. There's even evidence that people with bigger brains tend to
have higher intelligence.

No disagreement here.

But there has always been something opaque about I.Q. In the first place, there's no consensus about what intelligence is. Some people think intelligence is the ability to adapt to an environment, others that capacity to think abstractly, and so on.

Ah, the slippery slope begins. These arguments are so old, and well-answered in the literature that it is almost painful to repeat them. I refer the interested (and Mr. Brooks) to Seligman's phenomenal, non-technical introduction, as well as Deary's brilliant literary corpuscle. First, IQ and intelligence are two different things. One is a measuring instrument's scale and the other is a psychological construct that is measured, to one degree or another, by an IQ test. We don't confuse inches and paper, so why do we confuse IQ and intelligence? Second, few scholars actually study intelligence. While the word might be used in common parlance, there is no common definition. Instead, most serious scholars study general intelligence (g) or one of its sub-constructs (e..g, fluid abilities, crystallized abilities; see here or here or here). Once you make the jump to g, the definition becomes much more consensual. There are technical debates (as there are in any branch of science), but it's measurement (by factor analysis of one flavor or another) is virtually undebated. For most purposes in daily life, it is OK to quasi-equate intelligence and g, as well as IQ scores and
intelligence, but they really are quite different concepts.

Then there are weird patterns. For example, over the past century, average I.Q. scores have risen at a rate of about 3 to 6 points per decade. This phenomenon, known as the Flynn effect, has been measured in many countries and across all age groups. Nobody seems to understand why this happens or why it seems to be petering out in some places, like Scandinavia.

IQ scores, across generations, need re-calibrated for valid comparisons. We have ways that do this very well (latent trait models), that have very sound theory behind them. You have to periodically re-calibrate your bathroom scale, and you have no question about what it is measuring; why should IQ be any different? As a side note, this phenomenon is not at all confined to IQ tests, and it has been known about in the psychometric literature for decades, although it is called item parameter drift there. Moreover, just because there is no consensus as to why cross-generational scores tended to rise in the mid-twentieth century, this does nothing to invalidate the validity of interpreting IQ scores within a generation.

I.Q. can also be powerfully affected by environment. As Eric Turkheimer of the University of Virginia and others have shown, growing up in poverty can affect your intelligence for the worse. Growing up in an emotionally strangled household also affects I.Q. One of the classic findings of this was made by H.M. Skeels back in the 1930s. He studied mentally retarded orphans who were put in foster homes. After four years, their I.Q.'s diverged an amazing 50 points from orphans who were not moved. And the remarkable thing is the mothers who adopted the orphans were themselves mentally retarded and living in a different institution. It wasn't tutoring that produced the I.Q. spike; it was love.

Brooks is telling all parents of children who have Mental Retardation or Borderline Intelligence that their children's low cognitive ability is a direct result of parental inadequacy. If these parents would love their children more, the Mental Retardation would go away. If I were king, I would mandate that any person with the gumption to make asinine statements like this do two things (a) read Spitz's chef d'oeuvre, and (b) spend a week with a family who have a child diagnosed with Mental Retardation. Not just a daily visit, but an in vivo experience. Then get back to me about how easy it is raise the cognitive ability of people with mental retardation.

By the way, Turkheimer's studies look at the ability of the environmental variance to modify heritabilty estimates. Specifically, people who grow up in more impoverished environment have a more variable environments, which, almost by definition, decreases heritability estimates. This is a very long cry from showing "growing up in poverty can affect your intelligence for the worse".

Then, finally, there are the various theories of multiple intelligences. We don't just have one thing called intelligence. We have a lot of distinct mental capacities. These theories thrive, despite resistance from the statisticians, because they explain everyday experience. I'm decent at processing words, but when it comes to calculating the caroms on a pool table, I have the aptitude of a sea slug.

What? A few paragraphs ago general intelligence existed, now it doesn't? Anyway, it is an awful shame when everyday experience does not map onto what data tell us: Beth Visser recently (gasp!) gathered data to test Gardner's theory. What did she find? Basically what John Carrol said she would find a decade ago: these multiple intelligence all positively correlate (sans kinesthetic intelligence) and a strong g factor can be extracted when the measures are factor analyzed.

I.Q., in other words, is a black box. It measures something, but it's not clear what it is or whether it's good at predicting how people will do in life. Over the past few years, scientists have opened the black box to investigate the brain itself, not a statistical artifact.

I wish I had the luxury of being able to write blatantly false statements in a national paper. There is over 100 years of empirical literature investigating the construct validity of IQ. There is also 100 years of literature examining what, and how well, IQ scores predict life outcomes. A simple perusing of Jensen's g factor or Brand's g factor (this one is even available for free!) would have sufficed here; but who wants data to interfere with a good opinion?

Now you can read books about mental capacities in which the subject of I.Q. and intelligence barely comes up. The authors are concerned instead with, say, the parallel processes that compete for attention in the brain, and how they integrate. They're discovering that far from being a cold engine for processing information, neural connections are shaped by emotion.

...and you can read books about journalism in which the subject of sophism barely comes up. Namely because the books are concerned about journalism, not logical arguments. Why would a cognitive scientist who is writing a book about attention necessarily include a chapter about intelligence? As a rule, cognitive scientists tend to be concerned with general processes, not individual differences. The field can learn much from each other, but they are concerned about very different areas of investigation.

Antonio Damasio of the University of Southern California had a patient rendered emotionless by damage to his frontal lobes. When asked what day he could come back for an appointment, he stood there for nearly half an hour describing the pros and cons of different dates, but was incapable of making a decision. This is not the Spock-like brain engine suggested by the I.Q.

By all means, lets infer from one person with severe brain damage to the entire population. But if we want to play this game, I had a patient once who had just started Kindergarten, but could do addition, subtraction, multiplication and long division (the latter of which he deduced how to do pretty much on his own). He did not need a school to teach him any of this, so lets get rid of elementary schools for everyone. After all, if my patient could figure out long division, so should every other 5 year old.

Today, the research that dominates public conversation is not about raw brain power but about the strengths and consequences of specific processes. Daniel Schacter of Harvard writes about the vices that flow from the way memory works. Daniel Gilbert, also of Harvard, describes the mistakes people make in perceiving the future. If people at Harvard are moving beyond general intelligence, you know something big is happening.

Harvard never was a bastion for the study of general intelligence. It was the University of London. In fact, except for Yerkes, Herrnstein, and, to some extent, Pinker, I can't think of too many profs. there who contributed much to the study of general intelligence. And since when did Harvard's Psychology department become the measuring stick by which the importance of a research agenda was measured? I'm sure much of the work they do there furthers the general field of psychology, but what makes their research more special than, say, Berkeley, Stanford, UT-Austin, etc.?

The cultural consequence is that judging intelligence is less like measuring horsepower in an engine and more like watching ballet. Speed and strength are part of intelligence, and these things can be measured numerically, but the essence of the activity is found in the rhythm and grace and personality — traits that are the products of an idiosyncratic blend of emotions, experiences, motivations and inheritances.

This paragraph is quite confusing, perhaps due to the mixing of automotive and ballet metaphors. I think Brooks is trying to tell his readers he thinks personality is important for modern culture. I agree. And that has absolutely no bearing on the importance (or lack thereof) of cognitive ability in the same culture.

Recent brain research, rather than reducing everything to electrical impulses and quantifiable pulses, actually enhances our appreciation of human complexity and richness. While psychometrics offered the false allure of objective fact, the new science brings us back into contact with literature, history and the humanities, and, ultimately, to the uniqueness of the individual.

What? First, psychometrics (and specifically, the study of cognitive ability) has always held as paramount the uniqueness of the individual. Second, how has the study of cognitive ability NOT shown the complexity of humanity? Sir Cyril Burt, one of the pioneers in the field, was enamored with the complexity of students he encountered while a school psychologist in London. In fact, he was such an ardent supporter of psychological measurement so that he could begin to quantify, and, ultimately, understand and predict, this variability(see a bibliography here). More modern techniques, such as fMRIs, extend the work of psychometrics, in that they add to our ability to quantify individual variability at a much more precise level. However the two are quite complementary. From here:

Despite the sometimes contentious controversy about whether intelligence can or should be measured, the array of neuroimaging studies reviewed here demonstrates that scores on many psychometrically-based measures of intellectual ability have robust correlates in brain structure and function. Moreover, the consistencies demonstrated among studies further undermine claims that intelligence testing has no empirical basis.

In the world of academia, to have your ideas printed in a reputable journal, you have to go through the peer-review process. While there are arguments for the pros and cons of this process, at least it frequently squashes ill-informed, blatantly false propaganda from reaching the masses. After reading op-ed like this, one wishes the NYT had a similar mechanism in place.

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Sunday, August 05, 2007

Climate and civilization follow-up   posted by agnostic @ 8/05/2007 07:12:00 PM

Recently I suggested that civilization flourishes in some areas of the world more than others, in part, because winged insects thrive more in environments that are lower in elevation and latitude. These insects are a key source of chronic infectious disease in humans, and having to deal with the recurring symptoms must sap some of your body's resources that could be used for "luxury" processes involved in societal innovation. I neglected to mention that what likely makes wingedness more common in such environments -- a higher degree of environmental heterogeneity -- likely selects for an increase in migratory features more broadly, not just in insects. So some small animal may be more migratory, and it could be carrying parasites or pathogens itself, or be harboring insects that carry pathogens. It's just a lot easier for disease vectors to make their way to you in such environments. And of course, it may be that the fatigue caused by hot, humid weather makes you less productive.

Since then, I looked again at Inductivist's analyses on White IQ in various regions of the US, based on GSS data. In the first two posts (here and here), he showed that adults in the Mountain (MTN) region score better than average on mean IQ and percentage of holders of college degrees. More interesting, though, is the post on IQ and geographical mobility. Although New England and the Mid-Atlantic far and away attract the smartest Whites, the smartest of all are the NE transplants who were raised in MTN. Moreover, none of the bottom 10 pairs consisted of a group that was raised in MTN. By contrast, even though 2nd place goes to those raised in East South Central and who moved to NE, those raised in ESC also occupy 4 of the bottom 10 spots.

Why does growing up in MTN appear to boost your IQ? Probably because the climate is less favorable to the spread of pathogens by vectors that are migratory. And that, again, is probably due to less environmental heterogeneity in that area -- the Rockies are cold, dry, and very high in elevation, all tied to greater environmental stability. That's surely one reason why Colorado in particular performs so well, and its state government should publicize the hell out of Inductivist's findings to draw in wealthy parents who want the best environment for their kids. "Baby Einstein" pre-schools won't accomplish squat, but being raised in the salubrious climate of the Rockies sure will. Even the hot areas in the southern part of MTN, which are less impressive than the northern areas, are not humid or sub-tropical but desert, which is characterized by little environmental change over time or across space.

You might think that the lower population density is also a factor, and that could be, but people raised in regions with high density make a good showing in Inductivist's ranking. Population density is more critical in influencing acute, contagious diseases like the flu or perhaps rarer and wilder stuff like schizophrenia. But it could be that adult IQ is more influenced by the presence of chronic infections that continually disturb the development process. As before, knowledge of which pathogens and which vectors are the culprit is not necessary to believe this idea: just knowing that the local ecology in region X favors such things far more so than in region Y is enough to suspect that diminished IQ in region X is at least partly due to infection.

Moving on to larger concerns, one puzzle that I admitted in the original post was South Asian civilization -- isn't that one of the nastiest places to be climate-wise? I should've investigated further, because the answer is "yes and no." The climates in the Subcontinent vary a lot more than I thought, as you can see in this climate map of India and this climate map of the world. But does climate correlate with degree of civilization in South Asia? Beats me, since I couldn't say which areas over the long-haul show more development than which others. However, I have catalogued below a list of the climates for the capitals of South Asian civilizations beginning in the Neolithic. I used the chronology of Wikipedia's History of India article for convenience, and looked up the capitals there as well.

I'll leave it up to the more historically informed to say whether the hypothesis is supported or not My rough impression is that the North has shown greater development over the past several thousand years, even though the civilizations of the South and Bengal have been no slouches, but that may be wrong in general or perhaps correct broadly but wrong in finer detail. One interesting exception to the rule of Southern climates being more tropical, though, is that of Bangalore -- the "Silicon Valley of India" -- which enjoys a semi-arid climate, lies higher above sea level than Madrid (920 m vs. 667 m), and is known as a "Garden City."

And yes, I know that the current climates where the earliest civilizations flourished might not be identical to what they were at the time, but Iran and the modern countries occupying the Fertile Crescent also have mostly arid or semi-arid climates nowadays. The point is that they didn't consist of tropical wet & dry climates like you find in Sub-Saharan Africa or the Amazonian rainforests.

Civilization (:capital) -- climate

Mehrgarh -- arid

Indus Valley -- arid, semi-arid

Mahajanapadas -- arid, semi-arid, humid sub-trop

Magadha: Rajgir -- humid sub-trop

Maurya: Patna -- humid sub-trop

Satavahana: Pune, Paithan, Amaravati -- humid sub-trop

Kushan: Charikar -- highland, semi-arid; Taxila -- semi-arid; Mathura -- semi-arid

Gupta: Ujjain -- semi-arid; Patna -- humid sub-trop

Pala: Varendra / Rajshahi area -- humid sub-trop; also trop wet & dry

Chola: Tiruchirappalli -- semi-arid, trop wet & dry; Poomphuhar -- trop wet & dry; Gangaikonda Cholapuram -- trop wet & dry

Delhi Sultanate -- semi-arid

Deccan Sultanates -- semi-arid, trop wet & dry

Hoysala: Belur, Halebidu -- trop wet & dry

Kakatiya: Warangal -- trop wet & dry

Vijayanagara -- semi-arid

Mughal: Agra, Delhi -- semi-arid

Sikh Confederacy -- semi-arid, humid sub-trop

Maratha: Pune -- trop wet & dry

Post-Independence: New Delhi -- semi-arid; Islamabad -- semi-arid; Dhaka -- humid sub-trop, trop wet & dry

NB: I left out the period of colonial India for a few reasons that you might object to. First, Europeans certainly cope differently with non-European climates than do the locals, and I want to see whether climate affects degree of civilization even for those who are most adapted to life there. And second, it's my understanding that Europeans were more concerned with establishing superior trading posts and practicing mercantilism than they were with encourgaging civilization per se in South Asia.

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Tuesday, July 17, 2007

The Elf vs. Cosma   posted by Razib @ 7/17/2007 09:47:00 PM

I just got an email that The Elf has decided to take aim at Cosma Shalizi's posts dismissing g & the heritability of IQ. Now, Cosma is an acquaintance of mine and we share some common interests, but here I hope the Elf and her kindred give him hell! Any GNXP readers with knowledge and spare time cycles should left the Elvenkind a helping hand.

Related: Tyler Cowen & Arnold Kling on IQ. And Michael Stansty too.


Sunday, May 13, 2007

Behavioral Economics and IQ   posted by Herrick @ 5/13/2007 06:13:00 PM

We all know that homo economicus fails as a complete description of human behavior, as the new field of behavioral economics makes abundantly clear. So while the homo economicus model does a good job explaining things like the interaction of supply and demand, the random walk nature of stock prices, and photo #16, it misses quite a lot of important facts about human behavior. By now, there's a rich literature on this, and any book you can find on the subject by Bowles, Camerer, or Thaler would give a good overview.

But of course, both h. economicus and h. behavioralis are ideal types--and so the question arises: Are some people more behavioral than others? Are some people more economistic that others? And is there any simple way to predict who will fit into which part of the spectrum?

Economists have started working on this question over the last few years, and right now I'll just stick to one small issue: Patience. The behavioralists have done a good job proving that people are generally much less patient than economic models predict. And recent work seems to show that smarter people are quite a bit more patient, a fact that may have important social implications.

In a recent study, Benjamin and Shapiro found that among Harvard undergrads, "A one-standard-deviation increase in mathematical performance raises the propensity to be patient by 18 percentage points, relative to a base of 28%." So if math scores rise by two standard deviations, patience more than doubles. Their summary:

In two laboratory studies [with Harvard students and Chilean high school students], we show directly that cognitive ability is associated with more standard time and risk preferences.

And what does "standard" mean to Benjamin and Shapiro? More like h. economicus.

Shane Fredrick of MIT showed much the same in this quite readable paper. He has a nice review of the earlier literature and in his own experiments found that "[t]hose who scored higher on the [cognitive reflection test] were generally more 'patient.'"

Both of those papers involve experiments with students playing for small sums of cash. This paper, published in what is arguably the top journal in economics, showed that when people were making decisions involving thousands of dollars, people with higher AFQT scores were much more patient.

The military drawdown program of the early 1990s provides an opportunity to obtain estimates of personal discount rates based on large numbers of people making real choices involving large sums. The program offered over 65,000 separatees the choice between an annuity and a lump-sum payment. Despite break-even discount rates exceeding 17 percent, most of the separatees selected the lump sum--saving taxpayers $1.7 billion in separation costs. Estimates of discount rates range from 0 to over 30 percent and vary with education, age, race, sex, number of dependents, ability test score, and the size of payment.

And when officers were broken down by careers, who were the most patient?


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Friday, April 27, 2007

Intercourse and Intelligence   posted by Jason Malloy @ 4/27/2007 05:19:00 PM

Tyler Cowen quotes from a new study testing the relationship between grades and delayed sexual activity.

Last December I passed a paper along to Razib showing that high-school age adolescents with higher IQs and extremely low IQs were less likely to have had first intercourse than those with average to below average intelligence. (i.e. for males with IQs under 70, 63.3% were still virgins, for those with IQs between 70-90 only 50.2% were virgin, 58.6% were virgins with IQs between 90-110, and 70.3% with IQs over 110 were virgins)

In fact, a more detailed study from 2000 is devoted strictly to this topic, and finds the same thing: Smart Teens Don't Have Sex (or Kiss Much Either).

The team looked at 1000s of representative teens grades 7-12 in the National Longitudinal Study of Adolescent Health and The Biosocial Factors in Adolescent Development datasets, both of which include an IQ test, and include detailed sexual experience questions ranging from hand-holding to intercourse. As with the other study there was a curvilinear relationship: students with IQs above 100 and below 70 were significantly less likely to have had intercourse than those in between. Also like the other study, they found teens with IQs ranging from 75 to 90 had the lowest probability of virginity (the authors note this is also the same IQ range where propensity towards crime peaks).

Depending on the specific age and gender, an adolescent with an IQ of 100 was 1.5 to 5 times more likely to have had intercourse than a teen with a score of 120 or 130. Each additional point of IQ increased the odds of virginity by 2.7% for males and 1.7% for females. But higher IQ had a similar relationship across the entire range of romantic/sexual interactions, decreasing the odds that teens had ever kissed or even held hands with a member of the opposite sex at each age.

While these authors leave off at grade 12th, it would seem plausible to expect that this relationship extends beyond high school. To explore this, plenty of interesting facts come from a 2001 campus sex survey by the joint MIT/Wellesley college magazine Counterpoint (PDF). Looking within and between colleges, IQ appears to delay sexual activity on into young adulthood.

By the age of 19, 80% of US males and 75% of women have lost their virginity, and 87% of college students have had sex. But this number appears to be much lower at elite (i.e. more intelligent) colleges. According to the article, only 56% of Princeton undergraduates have had intercourse. At Harvard 59% of the undergraduates are non-virgins, and at MIT, only a slight majority, 51%, have had intercourse. Further, only 65% of MIT graduate students have had sex.

The student surveys at MIT and Wellesley also compared virginity by academic major. The chart for Wellesley displayed below shows that 0% of studio art majors were virgins, but 72% of biology majors were virgins, and 83% of biochem and math majors were virgins! Similarly, at MIT 20% of 'humanities' majors were virgins, but 73% of biology majors. (Apparently those most likely to read Darwin are also the least Darwinian!)

Looking at this chart it would strongly appear that higher complexity majors contain more virgins than majors with lower cognitive demand. This paper provides me with GRE scores by academic discipline, and, in fact, the correlation between the percentage of virgins in each Wellesley major and the average 'Analytical' GRE score associated with the discipline is 0.60.

One reason we might guess that smarter people in high school, or in more challenging colleges or majors, delay their sexual debuts is because they are delaying gratification in expectation of future reward. Sexual behavior (or at least the investment needed to procure a partner or sustain one) may compete with time/resources required for other goals, and intelligent people may have more demanding goals. James Watson even hinted at this in a recent Esquire magazine piece:

If I had been married earlier in life, I wouldn't have seen the double helix. I would have been taking care of the kids on Saturday. On the other hand, I was lonely a lot of the time.

While sex may not be marriage, it may still require effort that intelligent people prefer to invest elsewhere. This would fit Aldus Huxley's alleged definition of an intellectual as a person who's found one thing that's more interesting than sex.

Another idea is that smarter people are more risk averse, and delaying these activities is a byproduct of enhanced concerns about unwanted pregnancy and disease. While not avoiding sexual behaviors, per se, they are just less likely to seek it out or consent to it for fear of the potential consequences.

Another idea is that smarter people are more religious or more ethically conservative, and are trying harder to wait for marriage to have sex.

Another idea, consistent with popular media portrayals of geeks and nerds (males at least), is that intelligent people actually want to have sex, but are simply less likely or unable to obtain willing partners because they are disproportionately viewed as unattractive or undesirable as partners.

Another idea is that intelligent people have lower general sex drives. This shouldn't be confused with the first theory, where their sex drives would be normal and they have greater self-restraint.

Some insightful digging by blogger Half Sigma into the General Social Survey, which also includes an abbreviated intelligence test, has turned up a number of associations that speak to these theories. The relationship between sexual activity and intelligence found across adolescence and young adulthood appears to continue on into adulthood proper.

Not only do intelligent people have a delayed onset of sexual behavior, Half Sigma found that they also have a lower number of premarital sex partners throughout adulthood (18-39). While this is consistent with the above theory that high IQ people are more religious and conservative, this is, of course, not true. Religiousness correlates with lower IQ, and as HS shows in the same post, intelligent people were also more likely to say that premarital sex was not immoral. (Leaving those who did think it was immoral to participate in the bulk of it!) Most of the other theories are still consistent with this finding though.

Perhaps more revealing, HS, also showed that intelligence correlates with less sex within marriage for the same age range. While still consistent with pregnancy fears and competing interests, lower sex drive seems like a better fit. In fact another revealing finding from the Counterpoint survey was that while 95% of US men and 70% of women masturbate, this number is only 68% of men and 20% of women at MIT!

Also the idea that more intelligent people are too busy for the opposite sex not just in 7th grade to college, but throughout adulthood and for their own spouse, seems unrealistic. In fact the GSS also shows (PDF) that smarter people spend more time socializing with their friends, indicating their hours aren't spent as uniquely isolated and narrowly channeled as the theory would require.

But lower sex drive and anxiety about sex's consequences can't be the whole story either. Half Sigma also showed that the smartest men in the GSS (approx. IQ >120) were also more likely to visit a prostitute. (Hardly indicative of cautiousness) This may suggest intelligent men are less able to find willing sex partners. Are smart men less attractive to women? Perhaps in some ways. For instance HS found that smart men were less likely to be athletic, and this paper shows, unathletic men and women have fewer sex partners. Athletic men, with more willing sexual partners are also less likely to visit a prostitute. Athletic activity gives men more masculine bodies, which are more attractive to women. A more masculine physique correlates with (PDF) an increased number of sex partners.

So intelligent people have lower libidos and less masculine physiques. What hormone is responsible for both sex drive and masculine builds? That's right: testosterone.

And two new papers suggest that testosterone may depress IQ. One team found that salivary testosterone levels were lower for preadolescent boys with IQs above 130 and below 70. (the same two groups most likely to be virgins in adolescence)

Another paper suggests that a gene responsible for androgen sensitivity and higher sperm counts may also create a tradeoff for intelligence.

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Saturday, April 14, 2007

IQ, height & Crooked Timber   posted by Razib @ 4/14/2007 08:08:00 PM

John Quiggin @ Crooked Timber has a post where he moots ideas re: IQ & height. If you're inclined to give dkane a helping hand, swing on over! Just remember, the gang @ CT are much, much, smarter than you, so tread lightly....

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Wednesday, April 04, 2007

New GRE cancelled - the cost of attempted gap-reduction?   posted by agnostic @ 4/04/2007 11:38:00 PM

The NYT reports that a completely revised GRE has been deep sixed, not merely delayed (read the ETS press release here). The official story is that there is some insurmountable problem with providing access to all test-takers, an issue apparently too complicated for ETS to bother trying to explain it to us. You figure, since this was such a huge project that was suddenly halted, they'd want to clearly spell out why they dumped it -- unless that's the point. Although I'm no mind-reader, the true reason is pretty obvious: the made-over test was designed to narrow the male-female gap at the elite score level, but this diluted its g-loadedness such that it couldn't reliably distinguish between someone with, say, a 125 IQ and a 145+ IQ, which is what graduate departments who rely on super-smart students worry about. Rather than admit that this psychometric magic trick went awry and lopped off a few limbs of g-loadedness, they spun a yarn about access to the test. [1]

To put this in perspective, for those who took the SAT before spring 2005 -- which is everyone here, I assume -- the New SAT now includes a Writing test with both multiple choice grammar questions and a 25-minute persuasive essay. No admissions committee is paying serious attention to this silly addition, although high schoolers obsess over it. The real changes are that the Math test no longer includes the "quantitative comparison" questions (column A, B, equal, can't tell?), and the flavor of the questions is a bit more "book smarts"-based than before. Also, the Verbal test (now called Critical Reading) has zero analogies, fewer sentence completions, and much more passage-based reading. The gutted portions are those that are more highly g-loaded, for sure in the Verbal test, and most likely in the Math test as well. [2]

We now ask why ETS intentionally stripped the SAT of some of its g-loadedness? Certainly not because they discovered IQ had little value in predicting academic performance, or that some items tap g more directly than others -- so why re-invent the wheel? Since scores on various verbal tasks highly correlate, this change cannot have affected much the mean of any group of test-takers. But if getting a perfect score required scoring correctly on, say, 10 easy questions, 5 medium, and 5 difficult (across 3 sections), a greater number of above-average students can come within striking distance of a perfect score if the new requirement were 10 easy, 9 medium, and 1 hard. I don't know exactly how they screwed around with the numbers, but that's what they pay their psychometricians big bucks to do. Now, reducing the difficulty of attaining elite scores, without also raising mean scores (as with the 1994 recentering), can only have had the goal of reducing a gap that exists at the level of variance, not a gap between means. This, then, cannot be a racial gap but the male-female gap, since here the difference in means is probably 0-2 IQ points, although male variance is consistently greater.

Certainly this reduces the power of the SAT to detect very brainy people -- those with an IQ of 145 or 160 or whatever big number you want -- but I can easily imagine that both ETS and elite universities such as Harvard were willing to trade off a bit of g-loadedness in order to close the male-female gap at the elite level. Harvard students wouldn't look stupider, of course: their prestige is based on their mean SAT score compared to those of others. And they probably have other ways of figuring out who is very brainy vs. fairly smart. (As an aside, this also explains why lots more high-scoring applicants will be rejected by top schools, another paradox that is easily, even if only partially, resolved by clear thinking.) Moreover, attending Harvard isn't all about having a 145 IQ -- a non-trivial number of their graduates will join professions that don't require eigth-grade algebra or sophisticated analysis (say, political office). So that, too, may lessen their concern over the SAT becoming somewhat less g-loaded.

Not so with the GRE -- those who score at the elite level here are hardcore nerds who are planning to do serious intellectual work, and elite graduate departments pay attention mostly to the applicant's intellectual promise. MIT's math department probably doesn't care that an applicant scored 650 on the Math portion but showed singular potential for leadership roles. So, I imagine something similar to the SAT make-over happened, only this time the professors and/or ETS' psychometricians discovered that it would make a joke of a test used to detect the very brainy in search of elite graduate work.

To make this concrete, let's assume that, among applicants to graduate school in the arts and sciences (i.e., future scholars, not professionals), males enjoy only a 0.1 SD advantage in mean IQ (or 1.5 IQ points), as well as a 0.05 SD advantage in their standard deviation. Then a test that is reliable up to 3 SD above the female mean will have 30% of those above this threshold being female. (For comparison with the real world, grad students at CalTech are 30% female.) Almost 10 percentage points can be gained by dumbing the test down so that it's only reliable up to about 2 SD, in which case 39% at the top will be female. Dumbing it down further so that it can only detect those 1 SD above the female mean just adds about 5 further percentage points; females will make up 45%. My guess is that they weren't foolish enough to toy around with a GRE that only tested up to an IQ of 115, but that they took a risk on some version that tested up to about an IQ of 130. Though that's just about enough to get you into MENSA, the real hullabaloo over sex disparities has raged within the halls of the uber-elite: Harvard (Larry Summers), MIT (Nancy Hopkins), Stanford (Ben Barres), and so on. At such an elite level, an applicant with an IQ of 130 would be like a 6'3 guy trying out for the NBA (whose mean height is 6'7). Although the NBA doesn't automatically weed out those 6'3 and under, surely the recruiters would protest to the manufacturers if their new-fangled measuring sticks only measured up to 6'3!

Pursuing this hunch, I picked up my Kaplan GRE self-study book and found out that they knew at least roughly what the new GRE was going to look like. Here were the proposed new question types for Verbal and Math:

Reading Comprehension (4 types)
Sentence Completion (2 types)

Word Problems (4 types)
Data Interpretation (2 types)
Quantitative Comparison (1 type, as before)

Notice the huge change in the Verbal test, which parallels the change in the SAT Verbal test: analogies are gone, and most of the test is reading comprehension. As for Math, they did keep the Quant Comps, but most of the new question types thereof sound too touchy-feely to be of good use: Word Problems include old-fashioned ones, plus "Free Response," "All That Apply," and "Conditional Table" (Kaplan admits they didn't know the exact names -- maybe the last was a contingency table type?). "Free Response" sounds like it would be more g-loaded since you can't rely on answer choices, but it definitely isn't, at least not if this type was to resemble its counterpart on the SAT. Here, you grid in your own answer, but only non-negative rational numbers can be gridded, precluding the use of any questions whose answer had a root or exponent or absolute value, whose trick hinged on the properties of positives vs negatives vs 0, whose answer was an equation or inequality, and most importantly whose point was abstract symbol manipulation (such as "solve for V in terms of p, q, and r"). Since females are better than males at calculation, and worse than males on more abstract math problems, "Free Response" is an easy way to obscure the male advantage at "thinking" math.

Not knowing much about what the other two new types of Word Problems are, I think it's still safe to say they were just as vacuous. In fact, the Data Interpretation problems were to come in 2 types: the old-fashioned one, and a new one called -- don't laugh -- "Sentence Completion"! For christ's sake, why not just turn some of the harder ones into Writing problems in disguise, where the test-taker corrects the grammar of a word problem rather than actually solve it! This psychometric flimflam is ultimately what all would-be gap-reducers must reduce themselves to, at least when the concern is the sex gap at uber-elite levels where those who matter will brook no nonsense over the basic tests being dumbed down.

[1] Since I'm pretty tired by now of writing about the "women in science" topic, for background info I'll just link to a very lengthy post of mine on point, plus Steven Pinker's debate with Elizabeth Spelke.

[2] See p.2 of the full PDF linked to in this post from the GNXP archives. It contains a graphic showing the g-loadedness of various cognitive tasks. Analogies are the most highly g-loaded verbal tasks, reading comprehension one of the least so (though still enough to validate its use on tests).

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Tuesday, March 13, 2007

Sleep Affects IQ   posted by Fly @ 3/13/2007 12:13:00 PM

Sleep Disorders Can Impair Children's IQs As Much As Lead Exposure

UVa researchers have been studying sleep disturbances in children with enlarged tonsils and adenoids for the past seven years. In a recent study, they discovered that youngsters who snore nightly scored significantly lower on vocabulary tests than those who snore less often.
According to Dr. Suratt, the vocabulary differences associated with nightly snoring are equivalent to the IQ dissimilarities attributed to lead exposure. "Studies show that, even at nontoxic levels, lead exposure can reduce a child's IQ by more than seven points," he notes.
In a series of studies involving six to twelve-year-olds, researchers have been piecing together a list of risk indicators. So far, snoring frequency combined with sleep lab results have proven to be the most reliable predictors of intellectual impairment and behavioral problems. Sleep duration and race appear to be important risk factors, too.

This study only shows correlation but when combined with research showing the importance of sleep for consolidating memories the story becomes interesting. Perhaps treatments that improve sleep quality will increase IQ?

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Wednesday, March 07, 2007

African IQs   posted by DavidB @ 3/07/2007 11:14:00 AM

lwka's excellent post below mentions (among other things) the low reported IQ in African countries.

When this came up on a previous occasion the question was raised whether mean IQ's of 70 or even lower for Africans were compatible with a 'black' mean IQ of 85 in the United States, after taking account of the mixed African and European ancestry of American blacks.

At that time I did a few sums and started writing a post, but never quite finished it. But I have dusted it off and posted it below the fold, as it still seems relevant.

First, some assumptions:

- for the sake of this discussion, I assume that all group differences are wholly genetic in origin. Of course, I don't believe this, and I'm not sure that anyone does.

- I assume that the observed mean IQ of white Americans, on current (2000-ish) norms, is 100, and that of 'black' Americans is 85

- I started by assuming that, on average, 'black' Americans have 20% white ancestry. However, having done all the calculations on this basis and written up the results, I found that a figure of 25% is also sometimes used (e.g. by Jensen). This seems rather high, (see the figures in Sandra Scarr's Race, Social Class and Individual Differences in IQ), but I have repeated the calculations on this basis as an alternative. Rather than present two sets of workings, I have just inserted the key alternative results in square brackets. Whether on the 20% or 25% basis, I assume that the white ancestry of 'blacks' is genetically representative of the white American population.

Needless to say, all of these assumptions could be discussed at length.

With these assumptions, if all genetic effects are strictly additive, with no dominance or epistasis, then the mean IQ of an unmixed 'black' population would be X, where .8X + .2(100) = 85, which gives the value X = 81.25 [or 80 on the alternative 25% basis]. This is the easy bit!

But it is unlikely that all the genes affecting IQ are purely additive. To consider the possible effects of dominance, let us assume that all genes affecting IQ have two alleles, H (High) and L (Low), with H dominant. To take the most extreme assumption for gene frequencies, maximising the effect of dominance in differentiating a 'pure' black population from a black-white mixture, let us assume that the white population is entirely homozygous for the dominant H, while the ancestral black population is entirely homozygous for the recessive L. The US mixed 'black' population would therefore have a gene frequency at each locus of 80% L and 20% H. In Hardy-Weinberg equilibrium this gives genotype frequencies of .64LL, .32HL, and .04HH. The phenotypic value of each locus in the US 'black' population would therefore be .64X + (.32 + .04)100 = 85, where X is the unknown phenotypic value of the 'pure' black population. This gives X = 76.56 [or 73.2 on the 25% basis].

This is not a realistic assumption for gene frequencies, since if it applied to all loci the 'pure' populations would be genetically uniform, which is obviously not the case. To consider a more plausible model for gene frequencies, suppose the frequency of H is 60% in the white population and 30% in a pure black population, so that the frequency of L is 40% in the white population and 70% in a pure black population (since the frequency of H + L must be 100% for each population.) For the US 'black' population the frequencies are therefore (.8 x 30%) + (.2 x 60%) = 36% for H, and 64% for L. The Hardy-Weinberg genotype frequencies for the white population are 36%HH, 48%HL, and 16%LL and for the US 'black' population (approx) 13%HH, 46%HL, and 41%LL. If we designate the phenotypic value of HH and HL as X (not to be confused with the previous X!) and of LL as Y, we get two equations as follows:

(.36 + .48)X + .16Y = 100
(.13 + .46)X + .41Y = 85

Solving these equations gives (approx) X = 109.6 and Y = 49.6 [or 110.4 and 45.4 on the 25% basis].

In a 'pure' black population with gene frequencies of 30% H and 70% L, and Hardy-Weinberg genotype frequencies, these results give a mean phenotypic value for the population of almost exactly 80 [78.5 on the 25% basis], as compared with 81.25 [80 on the 25% basis] if there is no dominance. It will be seen that in this model the effect of dominance in differentiating 'pure' from 'mixed' black population is not very great.

These are in principle the values for a single locus. In the absence of epistasis, the mean value for the genome as a whole is simply the mean value of all relevant loci.

Epistasis, by definition, means that the phenotypic value of the genome varies according to the particular combination of genes at different loci. Essentially the only limit on possible epistatic effects is the ingenuity of the model-maker. As a general rule, epistasis is less important than dominance, so my gut feeling is that epistasis, on any plausible model, is unlikely to make much difference to the conclusions above. If anyone disagrees, let them set out a plausible model in which it does make a difference. Note that if high white IQ is due to favourable epistatic gene combinations, these are very likely to be broken up in a 'black' population with only 20% or 25% white ancestry, so that in this respect the difference between a 'pure' black population and the US 'black' population would probably be small.

Departures from Hardy-Weinberg equilibrium would also be a complication. Assortative mating within the US 'black' community for traits deriving from white ancestry, such as skin colour or IQ (assuming that this is genetic), would tend to increase the proportion of homozygotes above the Hardy-Weinberg expected levels. This would reduce the overall phenotypic contribution of white ancestry, since the same number of dominant H genes would be distributed among fewer individuals than in Hardy-Weinberg equilibrium. In effect, one of the dominant genes is 'wasted' in a homozygote. On the other hand, first generation black-white hybrids would have a higher proportion of heterozygotes than the rest of the 'black' population. One prediction of a purely genetic model assuming dominance for high-IQ genes is that the IQ of first-generation mixed-race individuals would be closer to the white mean IQ. But this would presumably affect only a small proportion of the 'black' population as a whole.

I haven't bothered calculating the effects on the assumption that the genes for low IQ are dominant. Obviously in that case the 'mixed' black population would be closer to the 'pure' black population.

The general conclusion is, I think, that on hereditarian assumptions about the nature of the black-white IQ difference in the US, the genetic IQ of a 'pure' black population cannot be much below 75 and is more likely around 80. (Note that this is by present-day norms. Due to the Flynn Effect, a present-day score of 80 would have corresponded to about 100 when IQ tests were first established.) This is higher than the mean IQ (often below 70) sometimes reported for black African countries from which the black ancestry of 'black' Americans is derived. Of course, one could in principle argue that the Africans who were taken to the US were above average in genetic IQ (relative to other Africans), but this is hardly likely. Alternatively, one could argue that 'black' Americans have improved their genetic IQ, and/or that African genetic IQ has deteriorated, in the 250 years or so since the slaves arrived in America. Neither hypothesis seems plausible.

It would therefore be difficult to consistently maintain a purely hereditarian view of both the black-white difference in the US and the low measured IQ of black Africans. I am not sure that anyone has actually take this position, but it may still be worth pointing out the difficulties.


Tuesday, March 06, 2007

Validity of national IQ   posted by the @ 3/06/2007 08:11:00 PM

In IQ and the Wealth of Nations (2002; IQatWoN) and IQ and Global Inequality (2006; IQGI), Richard Lynn and Tatu Vanhanen (L&V) present measurements and estimates of average national IQ (national IQ). In IQatWoN, L&V argue that national IQ predicts per-capita GDP (sup Fig 1). In IQGI, L&V argue that national IQ predicts quality of life measures (sup Fig 2). A common criticism of both works is to question the validity of national IQ. This criticism is motivated in part by the very low scores reported for countries in sub-Saharan African. A look at the distribution of national IQ is instructive (Fig 1).

Figure 1. The distribution of national IQ values (192 countries from IQGI).

L&V address the issue of validity by comparison of national IQ values with international test scores in math and science such as TIMSS and PISA. IQGI presents data from 10 different tests, with different scoring scales, in the form of 3 tables. To get a better grasp on the question of the validity of national IQ, I reanalyzed the test score data from IQGI. For better comparison, I renormalized each set of test scores relative to the maximum test score for each assessment. This is an imperfect but sufficient technique. An unweighted average of the available test score data was used to calculate a composite national test score for the set of 62 countries for which at least 1 test score was available (Fig 2).

Figure 2. The association between national test scores and national IQ for 62 nations.

National test scores are available for a limited range of national IQ scores, with few test scores available for countries with national IQs below the mid 80s. I interpret this to mean that for countries with national IQs below ~85, the test score data is insufficient to inform the question of validity. However, for the available scores (i.e., mostly above ~85), the relationship between national IQ and national test scores is very strong (see Sup Table 1).

The validity of sub-80 national IQs is addressed in part by the finding that IQ correlates with GDP and QHC (Sup Figs 1,2) throughout the observed range of IQ.

Update: Although there are only four values, the sub-80 national IQs are outliers, all with positive residuals. While this is hardly informative, it trends in the direction of casting doubt on the validity of sub-80 national IQ values.

Supplemental Figure 1. National IQ correlates with GDP per-capita (192 countries from IQGI).

Supplemental Figure 2. National IQ correlates with a L&V's quality-of-life index (QHC; 192 countries from IQGI).

Supplemental Table 1. Correlation matrix for national IQ (IQ), national test score (Test), L&V's quality of life index (QHC) and log per-capita GDP (logGPD) for 62 countries.
r QHC logGDP IQ Test
QHC 1 0.898936 0.7933265 0.7803476
logGDP 0.898936 1 0.760138 0.7565582
IQ 0.7933265 0.760138 1 0.9008035
Test 0.7803476 0.7565582 0.9008035 1

Related papers:
* Earl Hunt and Werner Wittmann, National intelligence and national prosperity, Intelligence, In Press --examines PISA scores
* Richard Lynn and Jaan Mikk, National differences in intelligence and educational attainment, Intelligence, Volume 35, Issue 2, March-April 2007, Pages 115-121. --examines TIMSS scores

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Thursday, February 22, 2007

Race IQ and SES   posted by the @ 2/22/2007 12:31:00 AM

Jensen (1998) makes a point that is worth repeating:
The pernicious notion that IQ discriminates mainly along racial lines, however, is utterly false.

Jensen presents what should be a predictable pattern for a highly heritable trait:
Source % of Variance Average IQ Difference
Between races (within social classes)
14 30 12
Between social classes (within races)
8 6
Interaction of race and social class
Between families (within race and social class)
26 65 9
Within families (siblings)
39 11
Measurement error
5 4
100 17

This can be demonstrated most clearly in terms of a statistical method known as the analysis of variance. Table 11.1 shows this kind of analysis for IQ data obtained from equal-sized random samples of black and white children in California schools. Their parents' social class (based on education and occupation) was rated on a ten-point scale. In the first column in Table 11.1 the total variance of the entire data set is of course 100 percent and the percentage of total variance attributable to each of the sources6 is then listed in the first column. We see that only 30 percent of the total variance is associated with differences between race and social class, whereas 65 percent of the true-score variance is completely unrelated to IQ differences between the races and social classes, and exists entirely within each racial and social class group. The single largest source of IQ variance in the whole population exists within families, that is, between full siblings reared together in the same family. The second largest source of variance exists between families of the same race and the same social class. The last column of Table 11.1 shows what happens when each of the variances in the first column is transformed into the average IQ difference among members of the given classification. For example, the average difference between blacks and whites of the same social class is 12 IQ points. The average difference between full siblings (reared together) is 11 IQ points. Measurement error (i.e., the average difference between the same person tested on two occasions) is 4 IQ points. (By comparison, the average difference between persons picked at random from the total population is 17 IQ points.) Persons of different social class but of the same race differ, on average, only 6 points, more or less, depending on how far apart they are on the scale of socioeconomic status (SES). What is termed the interaction of race and social class (8 percent of the variance) results from the unequal IQ differences between blacks and whites across the Spectrum of SES, as shown in Figure 11.2. This interaction is a general finding in other studies as well. Typically, IQ in the black population is not as differentiated by SES as in the white population, and the size of the mean W-B difference increases with the level of SES.

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Sunday, February 11, 2007

Horizontal g   posted by Alex B. @ 2/11/2007 01:54:00 AM

Wherever the abilities involved are sufficiently distinct--and that is in the great majority of cases--our tetrad equation is satisfied with surprising exactitude, so that here each ability must be divisible into g and s. The letter g becomes, in this manner, a name for the factor--whatever it may be--that is common to mental tests of such a description. This is the very definition of g. (Spearman, 2005, p. 161)

General intelligence (g) has been one of the most, if not the most, aggressively studied constructs in psychology. Type the search string "general intelligence" in PsycInfo and you will return over 2000 entries, and a similar search in Pubmed pulls up over 400. If you broaden the term to just "intelligence", the respective number of entries are 65405 and 37166. While not all of the results focus on g , (e.g., AI, "social intelligence"), a large portion of them do, and the prospect of meandering your way through can be intimidating. Fortunately, the overall literature is consistent and, at least for me, highly engaging.

The study of g can be bifurcated into two distinct areas: vertical and horizontal g . Vertical g is the domain that studies g's biological relationships. It is the area that is going to eventually assimilate enough data and literature to elucidate, unquestionably, the causal mechanisms of g . From this field of study, we know that g is correlated with a variety of neural mechanisms, such at glucose metabolism (Haier, 2003), cortical development (Shaw et al., 2006), and biochemical activity (Jung et al., 2005). We know that g is highly heritable, both when measured psychometrically (Plomin & Spinath, 2002) or chronometrically (Beaujean, 2005). We know that g decreases with inbreeding (Jensen, 1983) and increases with hybrid vigor (Nagoshi & Johnson, 1986). As genome scanning becomingmore popular, we are now even beginning to see some specific genes that are implicated g.

As interesting as vertical g is, however, this entry is going to instead focus in the horizontal aspects of g . That is, how does g play out into "everyday life." Specifically, we will look three different, although related, areas: education, occupation, and general life outcomes. The reasons for doing so are twofold: (a) the more the science of horizontal g is positively promulgated, then, perhaps, the more likely people are to support the needed research into vertical g and (b) even though this area of research has been around for over a century (e.g., Galton, 1869), there are still new, important findings.

Before delving into horizontal g, however, it would behoove us to delineate a mechanism by which g could influence education, occupation, and general life outcomes.For our purposes, that mechanism is information processing. Generally defined, information processing is the pathway and mechanisms by which stimuli are perceived, attended to, retrieved, and/or used to solve problems and/or cope with exigencies in the environment (Jensen, 1998a). The cognitive psychology literature is chalked full of the nuances of the various information-processing theorists, the specifics are which cannot be delineated here (an easy-to-read intro: Ormrod, 2004). Yet, within all these theories lies the idea that people respond to stimuli in a way that involves many mechanisms (e.g., sensory register, primary memory)and a variety of neurological regions (e.g., hippocampus, amygdala, mammillary bodies). The consequence? There is ample room for individual differences in the speed and efficiency in which information is processed.

From another perspective (e.g., Kline, 1998), information is processed in irreducibly small pieces (often called bits) and the time it takes to process those bits is the BIP, the Basic period of Information Processing. Now, the time it takes Johnny to process the fact that the only integer between 2 and 4 is 3 is going to be different than the time it takes Jane. Multiply those differences by the number of people processing the fact, and voila! individual differences.

Educational Outcomes

This is probably the area most replete with data and, unsurprisingly, the g-educational achievement relationship is strong. In fact, although it differs by grade level (with it decreasing as grade level increases), most of the non-random variance in scholastic performance is accounted for by g (Thorndike, 1984). Jensen (1989, 1998b) writes that this is so due to the fact that "school learning" is, itself, quite g -loaded. Of course, there are those who write that g is just a product of education (e.g., Ceci, 1991; for a review of others, see Gottfredson, 1986), or, perhaps more egregious, that g and educational achievement are just products of the tests designed to measure them (for review and rebuttal, see Jensen, 1984). But these arguments quickly dissipate when looking at the evidence.

For example, in the latest issue of Intelligence, there were two longitudinal studies (Deary, Strand, Smith, & Fernandes, 2007; Watkins, Lei, & Canivez, 2007) that showed a strong IQ --> Educational Achievement relationship (approx. 70 from Deary), but reverse (i.e., EA --> IQ) was not there (from the Watkins study). Further evidence comes from the two major "We can improve you Education by improving your IQ" projects: Head Start and the Abecedarian Study. With regard to the former, Head Start just does not produce long-term IQ gains and, hence, does not produce long-term academic gains (Caruso, Taylor, & Detterman, 1982; Holden, 1990; Kreisman, 2003). With regard to the latter, while there has been acrimonious debate, the overall conclusion is that, like Head Start, the initial IQ gains do not last, giving even more evidence that educational achievement cannot be raised independently of g (Spitz, 1986, 1992, 1993b, 1993a).

Yet another line for arguing against the prominence of g in education is the idea that there are other traits that are just as necessary for academic success, such as motivation, personality, etc. To risk sounding like to broken record, the data shows that these traits are not nearly as potent predictors as g in predicting academic outcomes. For example, Gagne and St. Pere (2002) gives us reason to believe that motivation might just be an impotent variable in predicting academic achievement. Likewise, Laidra, Pullmann, and Allik (2007) have shown that while personality factors contribute some to the variance in educational achievement, they are dwarfed in comparison to the contribution of g.

Occupational Outcomes

There are many theories as to how g and occupational outcomes relate (see Gottfredson, 1986), but the one that is most supported by data is best explicated by Frank Schmidt and John Hunter

[g] predicts both the occupational level attained by individual and their performance within their chosen occupation. [g] correlates above .50 with later occupational level, performance in job training programs, and performance on the job. Relationships this large are rare in psychological literature and are considered "large" . . . weighted combinations of specific aptitudes (e.g., verbal, spatial, or quantitative aptitude) tailored to individual jobs do not predict job performance better than [g] measures alone, thus disconfirming the specific aptitude theory. It has been proposed that job experience is a better predictor of job performance than [g], but the research findings . . . support the opposite conclusion. . . . Nearly 100 years ago Spearman (1904) proposed that the construct of [g] is central to human affairs. The research . . . supports his proposal in the world of work, an area of life critical to individuals, organizations, and the economy as a whole.(Schmidt & Hunter, 2004, p.171; cf.Schmidt & Hunter, 1998)

One could argue that, given the high g -education relationship, that the g-occupation relationship is just a natural outgrowth.That is, once education is controlled, the g-occupation relationship significantly shrinks. But to make that argument, one would have to have a Sternberg-like approach to intelligence (Sternberg & Wagner, 1993). That is, that the cognitive skills needed for a successful education are somehow vastly different than those needed for everyday life. The data, however, indicate that the same generative process that tends to makes one successful in the educational arena is also the mechanism that tends to make one successful in the occupational arena: g (Kuncel, Hezlett, & Ones, 2004). This is not to say that other things are not important in occupational or educational outcomes; but, as with education, they are not nearly as potent predictors (Gottfredson, 2002).

Life Outcomes

Over the last decade or so, an area that has become of more interest to the intelligence community is the influence of g on general life outcomes. That is, beyond educational and occupational outcomes, does g contribute to life success? The answer here, too, seems to be a resounding yes.

IQ scores [a proxy for g] predict a wider range of important social outcomes and they correlate with more personal attributes than perhaps any other psychological trait. The ubiquity and often-considerable size of g's correlations across life's various domains suggest g truly is important in negotiating the corridors of daily life. (Gottfredson, 2003, p. 326)

But how does g relate to general life outcomes? Believe it or not, it appears that the same information-processing mechanisms that are so potent for educational and occupational outcomes also play a role in day-to-day life (Gottfredson & Deary, 2004). Gottfredson (2003, 2004b) elaborates this mechanism as follows: Life is is made up of many tasks with a wide array of complexity (Gordon, 1997). In the US and most Western nations, society is "free enough" for competence (read: g ) to make a substantial difference in who succeeds in life. As those who have "higher g" are more able to tackle the day-to-day activities of life successfully with less exerted effort, they are able to progress in life with fewer impediments (e.g., untreated illness, accidents; Gottfredson, 2004a), thus allowing them to (a) have more resources to successfully compete and (b) be able to use their resources more efficiently. This then not only allows for a higher probability of achieving satisfying life outcomes (e.g., adequate income, occupational autonomy), but also allows for a lower probability of being involved with unsatisfying life outcomes (e.g., having children without means to support them, crime/delinquency) (cf. Ellis & Walsh, 2003; Herrnstein & Murray, 1996)


Given the ubiquity of g in fostering success in many life outcomes from education achievement to occupational success, from health outcomes to criminal recidivism, social science in general and psychological science in particular would be remiss to "pretend it doesn't matter" (Gottfredson, 2000). Rather, if these fields want to strengthen their scientific integrity and acumen, they should do exact opposite. That is, bring the large, cumulative database on g and its influence on life outcomes to the forefront of a wide array of research agendas so that this corpus of data can serve as the strong underlying foundation of a generation of new investigations on g's life implications. While this line of investigation may never get to the underlying (vertical) mechanisms by which g operates, it can help foster the acceptance of doing such research and pave the way for its societal implications, whatever they may be.


Beaujean, A. A. (2005). Heritability of mental processing speed as measured by mental chronometric tasks: A review and meta-analysis. Intelligence, 33, 187-201.

Caruso, D. R., Taylor, J. J., & Detterman, D. K. (1982). Intelligence research and intelligent policy. In D. K. Detterman & R. J. Sternberg (Eds.), How and how much can intelligence be increased? (pp. 45-65). Norwood, NJ: Ablex.

Ceci, S. J. (1991). How much does schooling influence general intelligence and its cognitive components? A reassessment of the evidence. Developmental Psychology, 27, 703-722.

Deary, I. J., Strand, S., Smith, P., & Fernandes, C. (2007). Intelligence and educational achievement. Intelligence, 35, 13-21.

Ellis, L., & Walsh, A. (2003). Crime, deliquency, and intelligence: A review of the worldwide literature. In H. Nyborg (Ed.), The scientific study of general intelligence: Tribute to Arthur R. Jensen (pp. 343-365). New York: Pergamon.

Gagne, F., & St. Pere, F. (2002). When IQ is controlled, does motivation still predict achievement? Intelligence, 30, 71-100.

Galton, F. (1869). Hereditary genius: An inquiry into its laws and consequences. London: MacMillan.

Gordon, R. A. (1997). Everyday Life as an Intelligence Test: Effects of Intelligence
and Intelligence Context. Intelligence, 24, 203-320.

Gottfredson, L. S. (1986). Societal consequences ofthe g factor in employment. Journal of vocational behavior, 29, 379-410.

Gottfredson, L. S. (2000). Pretending that intelligence doesn't matter. Cerebrum, 2, 75-96.

Gottfredson, L. S. (2002). g: Highly general and highly practical. In R. J. Sternberg & E. L. Grigorenko (Eds.), The general factor of intelligence: How general is it? (pp. 331-380). Mahwah, NJ: Erlbaum.

Gottfredson, L. S. (2003). g, jobs, and life. In H. Nyborg (Ed.), The scientific study of general intelligence: Tribute to Arthur R. Jensen (pp. 293-342). New York: Pergamon.

Gottfredson, L. S. (2004a). Intelligence: Is it the epidemiologists' elusive "fundamental cause" of social class inequalities in health? Journal of Personality and Social Psychology, 86, 174-199.

Gottfredson, L. S. (2004b). Life, death, and intelligence. Journal of Cognitive Education and Psychology, 4, 23-46.

Gottfredson, L. S., & Deary, I. J. (2004). Intelligence predicts health and longevity, but why? Current Directions in Psychological Science, 13, 1-4.

Haier, R. J. (2003). Brain imaging studies of intelligence: Individual differences
and neurobiology. In R. J. Sternberg, J. Lautrey, & T. I. Lubart (Eds.), Models of intelligence: International perspectives (pp. 185-193). Washington, DC: American Psychological Association.

Herrnstein, R. J., & Murray, C. (1996). Bell curve: Intelligence and class structure in American life. New York: Free Press.

Holden, C. (1990, March 23). Head Start enters adulthood. Science, 247, 1402.

Jensen, A. R. (1983). The effects of inbreeding on mental ability factors. Personality and Individual Differences, 4, 71-87.

Jensen, A. R. (1984). Test validity: g versus the specificity doctrine. Journal of Social and Biological Structures, 7, 93-118.

Jensen, A. R. (1989). The relationship between learning and intelligence. Learning
and Individual Differences, 1, 37-62.

Jensen, A. R. (1998a). The g factor and the design of education. In R. J. Sternberg & W. M. Williams (Eds.), Intelligence, instruction, and assessment: Theory into practice (pp. 111-131). Mahwah, NJ: Lawrence Erlbaum.

Jensen, A. R.(1998b). The g factor: The science of mental ability. Westport, CN: Praeger.

Jung, R. E., Haier, R. J., Yeo, R. A., Rowland, L. M., Petropoulos, H., Levine, A. S., et al. (2005). Sex differences in N-acetylaspartate correlates of general
intelligence: An 1H-MRS study of normal human brain. Neuroimage, 1, 965-972.

Kline, P. (1998). The new psychometrics: Science, psychology and measurement. London: Routledge.

Kreisman, M. B. (2003). Evaluating academic outcomes of Head Start: An application of general growthmixture modeling. Early Childhood Research Quarterly, 18, 238-254.

Kuncel, N. R., Hezlett, S. A., & Ones, D. S. (2004). Academic performance, career
potential, creativity, and job performance: Can one construct predict them all? Journal of Personality and Social Psychology, 86, 148-161.

Laidra, K., Pullmann, H., & Allik, J. (2007). Personality and intelligence as predictors of academic achievement: A cross-sectional study from elementary to secondary school. Personality and Individual Differences, 42, 441-451.

Nagoshi, C. T., & Johnson, R. C. (1986). The ubiquity of g. Personality and Individual Differences, 7, 201-207.

Ormrod, J. E. (2004). Human learning (4th ed.). Upper Saddle River, NJ: Pearson.

Plomin, R., & Spinath, F. M. (2002). Genetics and general cognitive ability (g). Trends in Cognitive Science, 6, 169-176.

Schmidt, F. L., & Hunter, J. (1998). The validity and utility of selection methods in personnel psychology practical and theoretical implications of 85 years of research findings. Psychological Bulletin, 124, 262-274.

Schmidt, F. L., & Hunter, J. (2004). General mental ability in the world of work: Occupational attainment and job performance. Journal of Personality and Social Psychology, 86, 162-173.

Shaw, P., Greenstein, D., Lerch, J., Clasen, L., Lenroot, R., Gogtay, N., et al. (2006, Mar 30). Intellectual ability and cortical development in children and adolescents. Nature, 440, 676-679.

Spearman, C. E.(1904). "General intelligence": Objectively defined and measured.
American Journal of Psychology, 15, 201-292.

Spearman, C. E.(2005). The abilities of man: Their nature and measurement. New York: Blackburn Press (Original work published 1927).

Spitz, H. H. (1986). The raising of intelligence: A selected history of attempts to raise retarded intelligence. Hillsdale, NJ: Lawrence Erlbaum Associates.

Spitz, H. H.(1992). Does the Carolina Abecedarian Early Intervention Project prevent sociocultural mental retardation? Intelligence, 16, 225-237.

Spitz, H. H. (1993a). Spitzs reply to Ramey's response to Spitz's first reply to Ramey's first response to Spitz's critique of the Abecedarian Project. Intelligence, 17, 31-35.

Spitz, H. H. (1993b). When prophecy fails: On Ramey's response to Spitz's critique of the Abecedarian Project. Intelligence, 17, 17-23.

Sternberg, R. J., & Wagner, R. K. (1993). The g-ocentric view of intelligence and job performance is wrong. Current Directions in Psychological Science, 2, 1-5.

Thorndike, R. L.(1984). Intelligence as information processing: The mind and the computer. Bloomington, IL: Center on Evaluation, Development, and Research.

Watkins, M., Lei, P. W., & Canivez, G. L. (2007). Psychometric intelligence and achievement: A cross-lagged panel analysis. Intelligence, 35, 59-68.

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Thursday, January 18, 2007

Murray on education and intelligence   posted by the @ 1/18/2007 02:31:00 PM

Charles Murray has a three-piece series of op-eds in the WSJ. They describe education policy recommendations for three levels of the IQ distribution:
  1. Intelligence in the Classroom: Half of all children are below average, and teachers can do only so much for them.
  2. What's Wrong With Vocational School? Too many Americans are going to college. 
  3. Aztecs vs. Greeks: Those with superior intelligence need to learn to be wise. 

The only criticism I can offer is the lack of citations/footnotes to support the many empirical claims made, especially in the first article, but I understand the venue does not permit it.

You can find plenty of criticisms on the web. At the Corner, Jonah Golderg criticizes Murray for being "dismissive of alternative or competing definitions of intelligence". Golberg's criticism is somewhat missing the mark by his framing in terms of "competing definitions of intelligence", but the IQ's corner blog offers a critique (and follow up) that appears to capture the spirit of Jonah's remark in more precise language. Jonah also confuses intelligence with wisdom -- a mistake worth pointing out. Hopefully Murray will find time to address his critics and publish a response in a venue where the underlying data can be examined more fully.

Another aspect of this worth pointing out: it is generally agreed that it is distinctly impolite to discuss differences in intelligence in public. However, this doesn't stop intelligence from being discussed in private, and is an unfortunate hamper to an important debate. In the comment threads of several recent posts we've discussed the issue of public discussion of non-PC topics. I would suggest that the intersection of intelligence and education falls into the class where the benefits of open debate far out weight the costs. As for getting over our discomfort with intelligence differences, I note that pharmaceutical companies have made major strides by getting commercials for embarrassing medical conditions onto prime time TV.


Tuesday, January 16, 2007

ASPM, Microcephalin, and intelligence   posted by p-ter @ 1/16/2007 04:05:00 PM

One of the papers mentioned before on the lack of association between the derived haplotypes at ASPM and Microcephalin and intelligence is now out. Here's the abstract:
Recent studies have made great strides towards identifying putative genetic events underlying the evolution of the human brain and its emergent cognitive capacities. One of the most intriguing findings is the recurrent identification of adaptive evolution in genes associated with primary microcephaly, a developmental disorder characterized by severe reduction in brain size and intelligence, reminiscent of the early hominid condition. This has led to the hypothesis that the adaptive evolution of these genes has contributed to the emergence of modern human cognition. As with other candidate loci, however, this hypothesis remains speculative due to the current lack of methodologies for characterizing the evolutionary function of these genes in humans. Two primary microcephaly genes, ASPM and Microcephalin, have been implicated not only in the adaptive evolution of the lineage leading to humans, but in ongoing selective sweeps in modern humans as well. The presence of both the putatively adaptive and neutral alleles at these loci provides a unique opportunity for using normal trait variation within humans to test the hypothesis that the recent selective sweeps are driven by an advantage in cognitive abilities. Here, we report a large-scale association study between the adaptive alleles of these genes and normal variation in several measures of IQ. Five independent samples were used, totaling 2,393 subjects, including both family-based and population-based datasets. Our overall findings do not support a detectable association between the recent adaptive evolution of either ASPM or Microcephalin and changes in IQ. As we enter the post-genomic era, with the number of candidate loci underlying human evolution growing rapidly, our findings highlight the importance of direct experimental validation in elucidating their evolutionary role in shaping the human phenotype.


Thursday, January 04, 2007

Sex difference in g   posted by the @ 1/04/2007 09:25:00 PM

A new La Griffe is up: Intelligence, Gender and Race.

Inspired by Jackson and Rushton (Intelligence 34 (2006) 479-486), La Griffe (Prodigy?) seeks to use a version of the "method of thresholds" to estimate the female distribution of g relative to males. The details are well spelled out in the article. Combining a variety of data sources, the article arrives at a least-squares estimate of the parameters defining the distribution of g first for blacks and then for women.

A white-black mean difference in g of 1.09 SD exists in favor of whites, equivalent to 16 IQ points. The black g distribution is narrower than the white, with a variance ratio (B/W) of 0.888.

A male-female mean difference in g of 0.164 SD exists in favor of men, equivalent to 2.46 IQ points. The female g distribution is narrower than the male, with a variance ratio (F/M) of 0.916.

Contrast the sex-difference estimate with Jackson and Rushton's estimate of 3.63 IQ points. At the time of publication of the Jackson and Rushton paper, I noted that no attempt was made to take into account the very well documented difference in variability of IQ between men and women. We can now compare Jackson and Rushton's estimate with La Griffe's. Above a +1 sd threshold, women would make up only 40% of the population using Jackson and Rushton's estimate and assuming equal variance. Notably, using La Griffe's estimates of mean and variance, women would make up 39% of the population above a +1 SD threshold.

Even small differences in mean and variance can have large effects at the tails. To give an idea of the effects, I've generated a table listing the percentage of women in a population above +1 SD for values of female mean in standard units (listed in the first column) and the ratio of female to male SDs (listed in the first row).

1 0.975 0.95 0.925 0.916 0.9 0.875 0.85
0 50% 49% 48% 47% 46% 46% 44% 43%
-0.025 49% 48% 47% 46% 45% 45% 43% 42%
-0.05 48% 47% 46% 45% 44% 43% 42% 41%
-0.075 47% 46% 45% 44% 43% 42% 41% 39%
-0.1 46% 45% 44% 42% 42% 41% 40% 38%
-0.125 45% 44% 43% 41% 41% 40% 38% 37%
-0.15 44% 43% 42% 40% 40% 39% 37% 36%
-0.164 44% 42% 41% 40% 39% 38% 37% 35%
-0.175 43% 42% 41% 39% 39% 38% 36% 34%
-0.2 42% 41% 39% 38% 37% 37% 35% 33%
-0.225 41% 40% 38% 37% 36% 35% 34% 32%
-0.242 40% 39% 38% 36% 36% 35% 33% 31%
-0.25 40% 39% 37% 36% 35% 34% 33% 31%
-0.275 39% 38% 36% 35% 34% 33% 31% 30%
-0.3 38% 37% 35% 34% 33% 32% 30% 28%


Tuesday, January 02, 2007

IQ → Academic Achievement   posted by Alex B. @ 1/02/2007 03:30:00 AM

Count 'em: one, two, three new studies on the relationship between IQ and academic achievement in the latest issue of Intelligence (volume 35, issue 1)

Before the studies' precis, a little background on why such studies are necessary. More than anything, such studies are needed because folks such as S. Ceci and R. Sternberg (very prominent and oft-cited) advocate that (traditional) IQ tests are just measuring little more than school related achievement. So, IQ and academic achievement are only related because, for reasons X, Y, and Z (pick your own environmental variables), some folks get more out of school, and it just so happens that the same folks do well on IQ tests due largely (if not entirely) because school achievement and IQ tests are measuring the same thing. Consequently, g is an irrelevant artifact of those damned psychometricians.

An alternative hypothesis (explicated nicely in Jensen1,2), however, is that due largely to genetic factors (which influence both individual differences and environmental influences), people enter school with wide variability in cognitive ability and "readiness to learn." This initial variability then heavily influences (although not completely determines) the amount a given student will pick up as he/she matriculates. As a student gains more information, his/her initial ability and the new information acquired then interact so he/she is able to expand his/her knowledge further, and so on and so forth. Therefore, while one needs access to "information," the child's general cognitive ability is the engine driving his/her educational achievement.

Don't miss the point here. These are two separate, testable, hypotheses. (A) IQ and academic achievement are synonymous. That is, people are smart (or not so smart) almost solely because they had (or did not have) a good education. (B) IQ is independent of academic achievement, although the former significantly influences the latter. That is, you can come from a good school, but not be so bright, and do poorly on achievement tests; likewise, you can come from a school that is not so good, (but meets some very minimum standard), but be bright, and do very well on academic achievement tests.

Now, the studies.......

1) Treena Eileen Rohde and Lee Anne Thompson: Predicting academic achievement with cognitive ability

This study is likely the weakest only because they used a group of college students from an elite university. Not that there is anything wrong with this, but when you see the samples in the studies below, it is a noticeable concern.

Their major contribution was that in predicting (standardized) academic achievement, speed of information processing and spatial ability can explain small, but significant, amounts of variance unexplained by general vocabulary (Mill Hill) and perceptual organization (Raven's Matrices), although the latter two tests, hands down, did the best in predicting academic achievement across various indicators.

In their own words:
General cognitive ability measures (Raven's, Vocabulary) and specific cognitive abilities (working memory, processing speed, spatial ability) collectively accounted for between 16% [GPA] and 54% [SAT] of the variance in academic achievement.

2) Marley W. Watkins, Pui-Wa Lei and Gary L. Canivez: Psychometric intelligence and achievement: A cross-lagged panel analysis

This study had 3 advantages over the former: (1) it is longitudinal, (2) the data is from a much wider scope of IQs, and (3) the data comes from all over the US. The drawback, and major caveat, is that the data is all from special education (broadly defined) testing, so the applicability to the entire population is in question. Still, the mean Full Scale IQ score from the WISC-III (the IQ instrument used) is 90 with a SD of 15 (in the general population it is 100 and 15), and the subtest scores hover around 8 with SDs that hover around 3 (in the general population it is 10 and 3).

Because they have longitudinal data on both standardized IQ and standardized achievement tests, they can specifically test the IQ--->Achievement hypothesis (see preamble). What do they find?

This notion of intelligence estimating a student's ability to succeed in school assumes the temporal precedence of intelligence to achievement. . . Regardless, the present study supports the view that intelligence, as measured by the VC [Verbal Comprehension] and PO [Perceptual Organization] dimensions of the WISC-III, influences or is related to future achievement whereas reading and math achievement do not appear to influence or are not related to future psychometric intelligence.

Stated more bluntly:

. . . the present study provides evidence that psychometric intelligence is predictive of future achievement whereas achievement is not predictive of future psychometric intelligence. This temporal precedence is consistent with the theoretical position of Jensen (2000)[1] that intelligence bears a causal relationship to achievement and not the other way around.

3) Ian J. Deary, Steve Strand, Pauline Smith and Cres Fernandes: Intelligence and educational achievement

Before getting on to the study, a brief word about Dr. Deary. He is the current badass of differential psychology. Because of his background (degrees in medicine and psychology), he is able to investigate psychometric, chronometric, genetic, and neurological aspects (often concurrently) of both intelligence and personality (look at the range on his vita). As if that were not enough, he has challenged the whole field of differential psychology by obtaining multiple population level, longitudinal data sets. So instead of trying to infer from a sample a few hundred to the target population, he is gathering population level samples of thousands of individuals. Case in point:

Deary's study looked at how cognitive ability measured at age 11 predicted academic achievement at age 16. Unsurprisingly, the IQ-Achievement correlations for the Sciences are around .6 (math highest, chemistry lowest), with similar coefficients form Arts/Humanities and Social Studies. Surprisingly, for practical fields (e.g., P.E., Art) the coefficients are a little lower, but not that much, averaging around .5. Here is a pic of the correlation table: (the n is in parentheses; it obviously changes as not every student took every class)

Deary took the analysis a step further however and did a little latent variable modeling. As the IQ test had three components/subtests (verbal, nonverbal, quantitative), he correlated a latent g factor with a latent academic factor using the following subtests: English, English Literature, Math, Science, Geography, French (n=12519). The correlation between the latent factors was .81. That is: 66% of the variance in latent (general) academic achievement can be explained by latent cognitive ability---measured 5 years previously. While he hypothesizes that such things as "school ethos" and "parental support" are good areas to search for the other 34%, based on Rohode's work, it is likely going to be found in residual, first order factors (see Carroll or McGrew).

Take home message: While general cognitive ability and academic achievement are not isomorphic, the former is necessary for the latter, while the converse is not necessarily true. Spearman suggested this more than a century ago, and, to quote the last sentence in Deary's work,
These data establish the validity of g for this important life outcome.

1. Jensen, A. R. (2000, August). The g factor and the design of education. Paper presented at the annual meeting of the American Psychological Association, Washington, DC.

2. Jensen, A. R. (1989). The relationship between learning and intelligence. Learning and Individual Differences, 1, 37-62.


Tuesday, December 19, 2006

IQ vs. hotness   posted by Razib @ 12/19/2006 11:07:00 PM

Here is my general model. Ignore the magnitude of the slope, I suspect the covariance between IQ & hotitude is rather modest indeed. Nevertheless, the graph illustrates my general model, a linear increase between 85 and 115, about 75% of the population. Then, a slight linear decrease up the IQ ladder (though beyond 140 you don't have too many people). Finally, below 85, and definitely below 75, a much sharper drop in attractiveness, and increase in phenotypic variance due to macroscale developmental instability.


Wednesday, November 29, 2006

Schizophrenia and IQ   posted by p-ter @ 11/29/2006 02:17:00 PM

Low IQ is a risk factor for developing schizophrenia, though the mechanism behind this association is somewhat unclear. A new study sheds a little light on this subject, and suggests the link might be genetic. The gene in questions is neuregulin 1, about which little is known. They find, first, that a regulatory SNP is associated with the development of psychotic symptoms in a particularly at-risk population (see part a above-- each bar is the percentage of subjects developing symptoms for a given genotype). They also find lower levels of activity in certain part of the brain in the patients with the TT genotype (see parts b and c above).

Further, here are the means and standard deviations of the IQ distributions of the different genotypes:

CC: 101.9 (8.4)
CT: 100.4 (9.4)
TT: 94.3 (6.9)

So this regulatory polymorphism could explain some of the natural variation in IQ.

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Friday, September 29, 2006

Skin color and IQ in the GSS   posted by the @ 9/29/2006 11:42:00 AM

A question from Jason Malloy prompted a quick search of the GSS for data on the cause of the Black-White IQ gap. In 1982, the GSS characterized the skin color of Black participants on a 5-point scale (1:very dark brown to 5:very light brown). The very dark/light categories consist of only 50 and 14 individuals, respectively, and so in the following analysis I merged them with the dark/light brown categories, to give three COLOR levels: dark, medium, and light. In the web application, use COLOR(r:1-2;3;4-5) instead of COLOR. The WORDSUM variable is a 10 question vocabulary test, which I'm treating as a proxy for IQ. It is correlated with educational attainment (~.4), and also correlates (~.4-.5) with tests of reasoning and basic knowledge that were given in some years. These other tests are not available for 1982. In the all-subject all-year GSS data set, WORDSUM varies by SEX, and in 1982 COLOR also varies by SEX. Thus, SEX is controlled for in each analysis. WORDSUM is lower in the youngest and oldest age groups, so an AGE(25-65) filter was used.

Table 1. Mean WORDSUM score by COLOR and SEX with ANOVA

Main Statistics
Cells contain:
-Std Devs
-N of cases
COLOR1: Dark4.15
2: Medium5.39
3: Light6.04

color indicates T-statistic, and thus p-value
Color coding:<-2.0<-1.0<0.0>0.0>1.0>2.0T
Mean in each cell:Smaller than averageLarger than average

Analysis of Variance

Main effects89.443.061329.8146.956.0002


We can quantify the effect size of each skin color class using Cohen's d statistic, which measures the mean difference in standard deviation units. In the 1982 dataset, the overall d for the Black-White gap on WORDSUM is -0.63 (among males d=-0.51, among d=-0.74). For comparison, the 1982 male-female gap among Whites is d=-.12, favoring females.

Table 2. Effect size (d) of COLOR on WORDSUM using "light" as a control group


We can also use Whites as the control group.

Table 3. Effect size (d) of COLOR on WORDSUM using Whites as a control group


Thus, there are substantial (moderate to large effect size) differences in WORDSUM scores between the darkest and lightest Blacks in 1982.

As reported by Rushton and Jensen (2005), Shuey (1966) reviewed 18 studies which used skin color as a measure of racial admixture to compare with IQ. Of those 18, 16 found a significant effect of the kind found here, but the overall correlation with IQ was low (r=.1). In this data, the COLOR WORDSUM correlation is r=.31 among males and r=.18 among females, with an overall correlation of r=.23. Off the top of my head, I'm not certain what the expected correlation would be between IQ and skin color among Blacks for a given measure of "between-group heritability" (BGH) as described by Jensen (1998). I'll leave it as an exercise for our mathematically skilled commentators to derive a formula for this relationship and to evaluate the signficance of this finding in explaining the cause of the Black-White IQ gap.

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Sunday, August 13, 2006

Narrowing of the white-black IQ gap?   posted by Darth Quixote @ 8/13/2006 03:07:00 AM

Some of you may have read the recent news report of a paper by William Flynn and James Flynn arguing that the white-black IQ gap has steadily narrowed over the last 30 years. I believe that this paper, as well as a rebuttal by Phillipe Rushton and Arthur Jensen, will be published in an upcoming issue of Psychological Science.

Our own resident educational psychologist Alex Beajuean is analyzing these and other relevant data using a model-based approach that is more sophisticated than the techniques used by Dickens and Flynn. We may deliver a report here at GNXP when this analysis is done. In the meantime, we have made a little graph showing the results of the studies conducted during the period covered by Dickens and Flynn, including those studies that Dickens and Flynn omitted from their analysis (and that Rushton and Jensen argue should have been included):

As you can see, the gap between white and black children does indeed seem to be decreasing over time. The gap between adults, however, does not show any noticeable trend. Perhaps the adults are lagging behind a true gain by blacks as a whole, but remember also that the correlation between genotypic and phenotypic IQ increases with age. Without further analysis, I suggest simply keeping this graph in mind as we go forward.


Tuesday, June 20, 2006

Fun with the GSS: Ghosts and IQ   posted by Jason Malloy @ 6/20/2006 10:47:00 PM

Bloggers Half Sigma and Inductivist are having ongoing fun with the General Social Survey data set: ethnic, gender, and religious comparisons galore! Half Sigma looks at the relationship between the GSS mini-IQ test and religious belief, and finds what we already knew.


Friday, June 16, 2006

Bruce Lahn moving on to non-IQ projects?   posted by agnostic @ 6/16/2006 11:35:00 AM

We'll have to wait and see, but it seems his interest in intelligence is wavering at present, so suggests a recent WSJ profile of his situation post-ASPM-MCPH1 (available below the fold).

Head Examined: Scientist's Study Of Brain Genes Sparks a Backlash
Dr. Lahn Connects Evolution In Some Groups to IQ Debate on Race and DNA 'Speculating Is Dangerous'
Antonio Regalado.
Wall Street Journal. (Eastern edition).
New York, N.Y.
Jun 16, 2006. pg. A.1

CHICAGO -- Last September, Bruce Lahn, a professor of human genetics at the University of Chicago, stood before a packed lecture hall and reported the results of a new DNA analysis: He had found signs of recent evolution in the brains of some people, but not of others.

It was a triumphant moment for the young scientist. He was up for tenure and his research was being featured in back-to-back articles in the country's most prestigious science journal. Yet today, Dr. Lahn says he is moving away from the research. "It's getting too controversial," he says.

Dr. Lahn had touched a raw nerve in science: race and intelligence.

What Dr. Lahn told his audience was that genetic changes over the past several thousand years might be linked to brain size and intelligence. He flashed maps that showed the changes had taken hold and spread widely in Europe, Asia and the Americas, but weren't common in sub-Saharan Africa.

Web sites and magazines promoting white "racialism" quickly seized on Dr. Lahn's suggestive scientific snapshot. One magazine that blames black and Hispanic people for social ills hailed his discovery as "the moment the antiracists and egalitarians have dreaded."

Dr. Lahn has drawn sharp fire from other leading genetics researchers. They say the genetic differences he found may not signify any recent evolution -- and even if they do, it is too big a leap to suggest any link to intelligence. "This is not the place you want to report a weak association that might or might not stand up," says Francis Collins, director of the genome program at the National Institutes of Health.

Several scientific groups have set out to disprove or challenge Dr. Lahn's discoveries. His own university now says it is abandoning a patent application it filed to cover a DNA-based intelligence test that drew on his work.

As scientific tools for probing genes become increasingly powerful, research into human differences has exploded. Most of the time, scientists are looking for clues about the causes of disease. But some research is raising tensions as scientists such as Dr. Lahn venture into studies of genetic differences in behavior or intelligence.

Pilar Ossorio, a professor of law and medical ethics at the University of Wisconsin, criticizes Dr. Lahn for implying a conclusion similar to "The Bell Curve," a controversial 1994 bestseller by Richard J. Herrnstein and Charles Murray. The book argued that the lower average performance by African-Americans on IQ tests had a genetic component and wasn't solely the result of social factors. Referring to Dr. Lahn and his co-authors, Prof. Ossorio says: "It's exactly what they were getting at. There was a lot of hallway talk. People said he's doing damage to the whole field of genetics."

The 37-year-old Dr. Lahn says his research papers, published in Science last September, offered no view on race and intelligence. He personally believes it is possible that some populations will have more advantageous intelligence genes than others. And he thinks that "society will have to grapple with some very difficult facts" as scientific data accumulate. Yet Dr. Lahn, who left China after participating in prodemocracy protests, says intellectual "police" in the U.S. make such questions difficult to pursue.

Scientists believe that a small group of anatomically modern humans struck out from Africa probably less than 100,000 years ago. After arriving on the Eurasian land mass, they continued to split up and eventually humans populated nearly every corner of the globe. One use of genetic research is to probe how each group evolved differently after becoming isolated from the others. Recently created genetic maps of people of African, Asian and European ancestry make that research easier.

For instance, researchers have found that most Europeans have a genetic variant that lets them fully digest milk as adults. The variant is much less common in Africa and Asia, where lactose
intolerance is widespread. Scientists theorize that it spread quickly among Europeans because drinking milk from domesticated dairy animals conferred a nutritional advantage. Similar evolutionary reasoning may explain why many people in malaria-prone parts of Africa carry gene variants linked to malaria resistance.

Other research is starting to explain variations in human skin color and hair texture. But scientists tense up when it comes to doing the same sort of research on the brain. Sociologist Troy Duster, who studies the use of racial categories by geneticists, worries that scientists will interpret data in ways that fit their prejudices. He cites the sorry history of phrenology, a study of skull shapes popular in the 19th century, and other pseudoscientific techniques used to
categorize people as inferior. "Science doesn't transcend the social milieu," says Dr. Duster, of New York University.

Dr. Lahn traces his interest in human differences back to his youth in China. Foreigners there used to have a special currency that they could use at stores closed to ordinary Chinese. "I wondered why people were different, and why Chinese were at the bottom," he says.

By the time violence struck Tiananmen Square in 1989, Dr. Lahn, the son of two physicists, was an undergraduate at Harvard University. He channeled his curiosity into genetics and built his reputation with a groundbreaking study of the Y chromosome. After taking a post at the University of Chicago in 2000, Dr. Lahn won a prestigious fellowship from the Howard Hughes Medical Institute.

The fellowship pays most of his research bills and has allowed him to pursue creative projects, often on attention-grabbing subjects. One study looked at how promiscuity among female chimpanzees, gorillas and humans affected the evolution of a gene that makes sperm sticky. "Bruce is in a hurry to be famous," says Martin Kreitman, a Chicago colleague who is friendly with him.

Henry Harpending, a University of Utah anthropology professor who recently published a theory for why Ashkenazi Jews tend to have high IQ's, says Dr. Lahn once suggested they co-author an article for Scientific American about the genetics of behavior, in which they could explain why "Chinese are boring."

"I think that Bruce doesn't understand political correctness," Dr. Harpending says. Dr. Lahn says he only vaguely recalls the conversation but confirms that he wonders whether during China's imperial times there was "some selection" against rebellious individuals.

In recent years, Dr. Lahn has become interested in why the human brain is so large and complex. Although humans and chimpanzees share about 96% of their DNA, human brains are about four times larger. Even today, researchers can find a correlation, on average, between
people's brain size and their IQ.

Dr. Lahn's group zeroed in on the role of two genes, called ASPM and microcephalin, that are known to have a role in brain size. Humans with defective copies of either gene are born with brains only about one-third the normal size.

Studying DNA from several species, the Chicago team found that, over millions of years, the genes had undergone more rapid change in monkeys, apes and humans than in other animals. Their next step was to determine if evolution had continued in modern humans. Dr. Lahn's graduate students began decoding DNA from 1,184 people belonging to 59 groups from around the world, including Bedouins, Pima Indians and French-speaking Basques.

The data showed that evolution had continued in recent millennia. A statistical analysis of DNA patterns suggested that new mutations in each of the two brain-related genes had spread quickly through some human populations. Evidently, these mutations were advantageous among
those populations -- just as the genetic variant promoting milk digestion was advantageous to early Europeans. Dr. Lahn and his team further observed that the new mutations are found most frequently outside of Africa.

What the data didn't say was how the mutations were advantageous. Perhaps the genes play a role outside of the brain or affect a brain function that has nothing to do with intelligence.

While acknowledging that the evidence doesn't permit a firm conclusion, Dr. Lahn favors the idea that the advantage conferred by the mutations was a bigger and smarter brain. He found ways to suggest that in his papers. One mutation, which according to his estimates arose some 40,000 years ago, coincided with the first art found in caves, the paper observed. The other mutation, present mostly in people from the Middle East and Europe, and estimated to be 5,800 years old, coincided with the "development of cities and written language."

That suggested brain evolution might have occurred in tandem with important cultural changes. Yet because neither variant is common in sub-Saharan Africa, there was another potential implication: Some groups had been left out.

The dean of the University of Chicago's medical school, James L. Madara, says he approached Dr. Lahn before the papers were published. They discussed whether the report could be taken out of context. "Let the chips lie where they may," Dr. Madara says he told Dr. Lahn. As long as
the ideas and data are clear, "don't worry about the implications," the dean said.

John Easton, head of media relations at the medical school, says his office was worried the work could be misinterpreted and abused by racist groups. Mr. Easton borrowed a copy of "The Mismeasure of Man," the famous attack on IQ tests and brain-volume measurements by the late paleontologist Stephen Jay Gould. Mr. Easton helped Dr. Lahn with talking points about his research. "We said, 'Don't be shy about telling people what it doesn't mean,' " Mr. Easton recalls.

Mr. Easton says Dr. Lahn "makes us nervous" but "with Bruce we know it's not driven by personal bias." That is because Asians "don't score at the top" in the frequency of the brain-gene mutations, Mr. Easton says.

Dr. Lahn's paper and talk at his university -- in which he also claimed the gene variants were probably linked to higher IQ -- provoked a strong reaction both on and off campus. Dr. Collins, head of the federal genome program, obtained advance copies of the papers and circulated them to top population geneticists. He wasn't persuaded by the statistical evidence for evolution and criticized Dr. Lahn's work in media interviews.

The papers won wide attention among researchers, and several responded by setting out to test Dr. Lahn's findings. Scientists at the Broad Institute, a top genetics center in Cambridge, Mass., have been reanalyzing some of the data and say they may challenge Dr. Lahn's finding that evolution acted on ASPM, one of the genes. Broad's influential chief, Eric Lander, says scientists probing recent evolution run the risk of "seeing a difference, and saying there is a story to fit

A team at the University of California, Los Angeles, recently tested whether the gene variants actually affect brain size. They studied DNA from 120 people whose brain volumes they had already measured using magnetic-resonance imaging. They didn't find any difference. "It
certainly makes you want to look at other explanations" of what the variations mean, says Roger P. Woods, a UCLA brain-mapping expert who reported the results in May.

Some of Dr. Lahn's co-authors are also uncomfortable with the work. Sarah Tishkoff, a geneticist at the University of Maryland who provided DNA from remote African groups, says she is bothered how one paper drew a link between the genetic changes and the rise of civilization. She
thinks it is too early to reach any conclusions about why the changes spread and says it is "very simplistic" to imagine that a single gene could have a major effect on complex cultural traits.

Several groups of scientists have sent letters to Science criticizing the papers. Dr. Lahn prepared responses, sending one earlier this month, but Dr. Tishkoff wasn't willing to add her name to them.

"You have to follow the data wherever it leads, but speculating in this field is dangerous," says Spencer Wells, head of the National Geographic Society's Genographic Project, a five-year, $40 million effort to collect DNA samples from 100,000 indigenous people. Dr. Wells says the project team might try to find evolutionary reasons for physical differences such as why Danes are taller than pygmies. But Dr. Wells says National Geographic won't study the brain. "I think there is very little evidence of IQ differences between races," he says.

The accuracy of Dr. Lahn's work and his views on race came up in his tenure review last fall, says a person familiar with it. After debate, his department voted unanimously in his favor, according to another faculty member. A more senior committee agreed and awarded Dr. Lahn the post of full professor, although it wasn't unanimous, this person says.

Dr. Lahn stands by his work but says that because of the controversy he is moving into other projects. Earlier this year, Mr. Easton of the university's media department forwarded Dr. Lahn a paper by two economists looking at the IQ of infants of different races. Dr. Lahn wasn't interested. "I'm surprised anyone studies this," he replied in an email.

Dr. Lahn says he isn't as eager as he once was to continue studying brain differences. P. Thomas Schoenemann, a professor of anthropology at the University of Michigan-Dearborn, says that at Dr. Lahn's request he collected DNA from 25 people whose brain sizes he had studied previously. But the two scientists haven't been in touch recently.

The university's patent office is also having second thoughts. Its director, Alan Thomas, says his office is dropping a patent application filed last year that would cover using Dr. Lahn's work as a DNA-based intelligence test. "We really don't want to end up on the front page . . . for doing eugenics," Mr. Thomas says.

More recently, Dr. Lahn says he was moved when a student asked him whether some knowledge might not be worth having. It is a notion to which he has been warming. Dr. Lahn says he once tried testing himself for which version of the brain genes he has. The experiment's outcome was blurry "but it wasn't looking good," he says. He hasn't tried testing himself again.


Tuesday, May 23, 2006

g and Creativity   posted by agnostic @ 5/23/2006 02:29:00 PM

I've been meaning to write this up for awhile now, so here goes. It's more of a pointer to what books & articles to read, so it may not cover every question you have about g and creativity. [1]

In Carroll's (1993) encyclopedia of cognitive abilities, Ch. 10 surveys psychometric data on the ability of "idea production" -- basically, creative thinking. It's a 2nd-stratum factor (called Gr for "general retrieval" ability), dominated by the 3rd-stratum general factor (g), thus a sister of the more well known visuospatial and verbal factors. Two of the 1st-stratum daughter factors that compose Gr are called FA (Associational Fluency) and FO (Originality/Creativity), which respectively measure how well you can draw associations between items in long-term memory (e.g., how interconnected your idea-web is), and how well you can devise novel solutions to problems (e.g., take ordinary objects & fashion new uses for them). Real-life tasks will also tap into Gc, or "crystallized" intelligence (the knowledge acquired as a result of applying g in academic / intellectual domains, e.g., vocabulary items, scientific ideas, etc.). So, given two individuals whose Gr is the same, the one with a larger store of ideas will have a richer web of associations.

Simonton (1999 Ch. 2 & 3; 2004 Ch. 3 & 5) argues convincingly that at root the creative process is like Darwinian selection: ideas are combined in blind variation, largely unconsciously; most of these combinations are useless, but a few show promise. These are then selected and elaborated on consciously, putting flesh on the inspiration. Simonton says that aside from the usual suspects of high intelligence (g) and a healthy store of ideas & facts to draw on (unspecified, but must mean Gc), another part of creativity is having a "flat" associative hierarchy -- connections between ideas criss-cross a lot, rather than respect a "steep" hierarchy like Linnaean classification schemes. This trait is essentially Gr, though he does not recognize Carroll's terminology nor that it is dominated by g.

This idea is originally due to Mednick (1962), whose Remote Associates Test measures how fluent one is in making remote associations. Ex: given the words "rat," "cottage", and "blue," they are all remotely related to "cheese" (the answer). French, Price, & Ekstrom's (1963) test has a subsection for idea production, one of whose tasks requires the subjects to fill in blanks to complete similes: e.g., "She was as pale as..." This test is a measure of diverse cognitive abilities, not just creativity, reflecting the consensus that there is no cognitive ability that is not influenced by g, and that all 2nd-stratum abilities correlate with each other. See Gottfredson (2003), where she tears Robert Sternberg a new orifice for lazily trying to argue that "practical intelligence" is different from and not correlated with g, one prong of his Triarchic theory of intelligence.

Now, a skeptic like Michael from 2blowhards could say: OK, sure, if you restrict "creative products" to those endeavors that demand braininess, by definition creative people will be brainy, whereas if you took a more liberal & inclusive view in which "creative products" included more popular forms where the cut-offs for g are more forgiving, this effect would shrink or vanish. So, is it possible to avoid this tautology? Yes: define "creative products" roughly as "forms which inspire a sense of awe or marvel in the beholder, as if such products were not thought possible to come from mere mortals." If that sounds too reverential, you can use more folksy language, but you get the idea. Call this the "Wow!" definition. It avoids any mention of cognitive ability, favoring only the ability of the work to inspire, rather than to provoke the beholder to complain, "Meh, my 3rd grade son coulda done that." It also cuts across disciplines: it captures why we find the Michelangelos & Beethovens more creative than illustrators & composers of advertising jingles, and the Newtons & Gausses more creative than "lab men" & those who report another example of a phenomenon with thousands of attested examples.

It may just so happen that humans are more wowed by feats of cognitive difficulty, but we didn't build this in -- it's just a quirk of human psychology. Martians might well be wowed by similes such as "The printer paper was as white as white printer paper." And it really is the cognitive part that we're wowed by -- no one but a boor would claim that Stephen King is a creative genius or super-intelligent based on his popularity / best-selling status. Even those whose personal tastes lead them to prefer King to Goethe are not confused about who is more creative or intelligent. They simply feel that King speaks to their tastes more than that arty-farty stuff.

So, rather than a creative / non-creative dichotomy, we have a spectrum of more or less creativity. The farther one moves toward the creative end, the higher the demands on g in general and Gr in particular; the more one moves toward the less original end, the more relaxed the demands, as one is no longer re-inventing the wheel. I should also amend the definition to include only those forms which more or less originate with the creator, rather than forms which result from the individual "following a script." Thus we exclude actors, orchestra members, and individuals who solve math homework problems by means of common algorithms (like long division), as they're fundamentally different from playwrights, composers, and mathematical discoverers / pioneers. We expect the latter to be smarter, while we don't expect the former to be smarter (which is not the same as expecting them to be dull!).

Lastly, intelligence -- whether g, Gr, or anything else -- is certainly not sufficient for high status in creative fields. Beginning with Galton, researchers of genius have noted that the distribution of "eminence" (a proxy for genius, as there are no unrecognized geniuses) is not the normal bell curve that we know and love, but rather log-normal. The less mathematically inclined can see pictures of what this looks like here; the more quantitative can read a nice pdf here on its use in the sciences, which has an excellent log-normal version of the Galton board. The key difference is that, while a normal curve is symmetric, the log-normal curve is skewed; for eminence, it is highly skewed, like the green or pink curves on the NIST link above. At first, you might think: "Well, maybe that's just the far, far-right tail of a bell curve -- the super-duper nerds." But the shape is not the same. If you look at the "slope" of the right half of a bell curve, it changes from "steep" descent to "shallow" descent pretty quickly -- by the time you got to the far-right tail, you would only see a shallow descent. With the log-normal curve, however, you see a change from steep to shallow, so it can't be the same as the far-right tail of a bell curve. ("Steep" and "shallow" refer to the absolute value of the slope (rise / run) at a point: if it's greater than 1, i.e. "rising" more than it's "running", call it steep; if it's between 0 and 1, i.e. rising less than it's running, call it shallow.)

So what's the big deal? Well, log-normal curves usually imply that there's a synergy among various components that produce the effect -- where the whole is greater than the sum of its parts. (Or: where the effects of the random variables involved are multiplicative rather than additive -- if the effects are additive, the result is also a normal bell curve.) To take a more concrete example, consider female facial beauty -- let's say there are 5 variables involved: eyes, lips, hair, prominence of bone structure, and rough facial geometry (e.g., long or short face). Assume there is a universal scale of less-to-more beautiful values for each variable (e.g., fuller vs thinner lips, larger vs smaller eyes, etc.). Also assume each variable would yield a normal bell curve. Now, in an additive model, you would take the points earned from each variable and sum them up -- so, the lips variable doesn't "see" or "care about" the eyes variable; you get X points for full lips no matter what. By the Central Limit Theorem, the sum of these 5 variables would itself be a normal bell curve -- on a scale of 1-9, most people would be a 5, and the percentages would drop off in both directions, so that there would be very few 2s or 8s. That's the opposite of reality, though: the percentage of 2s is far greater than that of 8s! This is because the variables "see" or play off of each other -- large eyes and full lips produce a more beautiful effect than if you just added their values together. Likewise, large eyes, full lips, lustruous hair, and prominent cheekbones -- 4 great qualities -- can all be brought crashing down by a long horse-face, rather than only suffer a slight reduction in beauty.

In the case of creativity, there are several ideas for what these other factors are that interact synergistically with intelligence -- e.g., the Big Five personality trait Openness, Eysenck's personality trait Psychoticism, schizotypal personality, and so on. This is another interesting area of creativity research, but it doesn't mean that intelligence is any less important as a result. Consequently, claims to the effect that "IQ doesn't matter in creative fields past a threshold of 120" are nonsense. It's hard to get large data sets for such situations since there are damn few Newtons and Beethovens alive to test. Moreover, let's say it turns out that when you do the multiplication of the variables for arts vs sciences, the intelligence variable is weighted more in the sciences than in the arts -- nevertheless, in any cognitively demanding area higher *g* always helps.

[1] For more background on g, sub-g factors, and brain correlates of g, see these two posts from the GNXP archives.


Carroll, J.B. (1993). _Human cognitive abilities: A survey of factor-analytic techniques_. Cambridge: CUP.

French, J.W., Ekstrom, R.B., & Price, L.A. (1963). _Manual and kit of reference tests for cognitive factors_. Princeton, NJ: ETS.

Gottfredson, L. S. (2003). Dissecting practical intelligence theory: Its claims and evidence. _Intelligence_, 31(4), 343-397.

Mednick, S.A. (1962). The associative basis of the creative process. _Psychological Review_, 69, 220-32.

Simonton, D. (1999). _Origins of Genius: Darwinian Perspectives on Creativity_. New York: OUP

------------- (2004). _Creativity in Science: Chance, Logic, Genius, and Zeitgeist_. Cambridge: CUP

Addendum: In the comments people are bringing up what I hope they wouldn't bring up, since it's a whole 'nother post, but I saw it coming! So a word or two about racial differences in creativity. First, unlike the copious data on the 1-SD difference in the means between Af-Ams and whites, there is no similar data on tests only of Gr, so all we have is speculation. That said, my guess is that, while not doing so well on g, Af-Ams do pretty well on Gr -- lopsidedness in the 2nd-stratum factors isn't unheard of. On average, Af-Ams and Ashkenazi Jews have greater verbal than spatial sub-scores; NE Asians are the reverse. Commenters have mentioned hip-hop music, but that's the wrong place to look -- Jazz for sure. Also, the popular phenomenon of "yo momma" jokes is basically a modified remote associates / similes test. True, you can cheat by stealing someone else's joke, but word gets around fast, and unoriginal jokes are quickly booed. You can see all this play out on the new MTV show "Yo Momma." The more remote the assocation, while still making sense, the higher the score; ditto for verbal cleverness. For example: "Yo momma sweat butter and syrup and got a job at Denny's wiping pancakes across her forehead." "Yo breath smell so bad the only dis I'm gonna give you is dis-infectant." And so on.

However, all of this is at the popular level, while what I was writing about was high culture -- so Jazz would still survive, but not the other stuff. If you want to include popular culture as well, these products don't inspire as much marvel in the beholder, so the cognitive difficulty (which is what really inspires awe) isn't as demanding. Thus, the g variable is weighted less, but remember: creativity results from multiplying together a host of factors. All I was arguing was that g was one of them, and likely heavily weighted. Some of these other factors may favor Af-Ams -- for example, people who reach high eminence in creative fields are usually more disagreeable than agreeable; at such heights, diplomacy is for suckers. Again, I'll take it for granted that the Af-Am mean is more in the disagreeable / confrontational direction than is the NE Asian mean. So that's in the Af-Ams' favor. But I also mentioned Openness to experience, and Af-Ams seem to be more conventional and less tolerant of novelty, fantasy, thrill-seeking, and so on (this difference is often the seed for black comics' jokes about how whacky white people are). On the plus side, that renders them more immune to New Age flimflam, yet it also is a penalty when we consider the factors involved in creativity.

As for NE Asians, they have higher g on average, their strength coming from superior visuospatial skills. So, look at how good they are at innovating in visual areas of pop culture (their poor turn-out as comedians, etc. would be due to lower verbal skills). I've mentioned before that they're pretty innovative when it comes to visual tasks, provided they're financially secure: graphic design, hell, any design, film, video games, and so on. But as for the Openness, Agreeableness, and schizotypal / eccentric-nutty behavior, I'd guess they tend to score in the direction penalized in the creativity multiplication. I'm sure some of this is cultural, but still, exposure to & incorporation into mainstream American culture still leaves the (correct) stereotype that NE Asians are more conformist than whites or Af-Ams. Less Open and more Agreeable individuals will appear more conformist. To the extent that there is a genetic component to these personality traits, then there will be a ceiling that they'll hit even when the cultural obstacle is removed.

These observations pertain as well to the male-female gap in creativity. This is particularly apropos given the Larry Summers fiasco. In order to show discrimination, you'd not only have to take into account the different variances in the male & female curves for g, but the potential differences in means and/or variances for all the other curves involved in the multiplication. Not only are males more likely to have an IQ of 155, but they're certainly more likely to be Disagreeable and schizotypal / eccentric (my guess: difference in means), as well as to be the more Open / daydreamer sort or exhibit nonconformity (my guess: difference in variances). If you look at the real loonies among scientists and artists -- mathematicians and composers -- they're so overwhelmingly male, the culprit can't be g only. In these fields, females are penalized not only for lower likelihood of reaching say IQ 155, but also for on average being more Agreeable & diplomatic, not Open enough (too practical), and not nutty or eccentric enough -- and remember, these penalties are multiplied or compounded, not merely added together.

It's hard to avoid the obvious: at the high culture level, males of Eurasian origin (as in, west of the Himalayas / Siberia) dominate more than would be expected just based on g, though that certainly plays a role too. My hunch is that, for whatever obscure reasons, their average values for each of the variables involved in the multiplication result in greater creativity than other demographic groups. Cultural factors can dampen or amplify this pattern to an undetermined extent, but those are the differences we're starting with. When we move down to the popular, less awe-inspiring level of culture, where the demands on g are less intimidating, then other groups will make greater headway -- again, following the pattern of their average cognitive profile (more verbal for Af-Ams and Ashkenazis, more visual for NE Asians).


Wednesday, May 10, 2006

EGHM II: what the hell is IQ?   posted by JP @ 5/10/2006 01:55:00 AM

Eco de Geus gave a talk on his search for endophenotypes for IQ. A bit of background: when searching for genetic factors involved in a phenotypic trait, it's easiest to look directly at the trait itself-- that is, if the trait is a disease, grab some sick people and some healthy people and compare the two groups.

A more powerful approach, however, is to look at something closer to "gene action", as they say; look at BMI instead of diabetes or QT interval as opposed to heart disease. It's easy to imagine why this works: instead of diluting your cases with people who have disease for multiple, distinct causes, you're looking only at one of them.

IQ, de Geus claimed, is a complex phenotype that would be amenable to this kind of approach. So he's been looking at various measures to bring IQ down to a more physiological level (using twin studies). But, well, he ain't there yet. Here are some results:

1. Speed of signal transmission in neurons: heritable, but not correlated to IQ

2. Processing speed (as measured by one of the waves in an EEG-- this is obviously not something I know much about): heritable, but not correlated to IQ.

3. Cortical connectivity: heritable, but not correlated to IQ.

4. Brain volume: heritable and correlated to IQ. But he said he didn't like this as an endophenotype because he found "high IQ --> big brain" to be a more plausible explanation for the correlation than "big brain --> high IQ".

5. The one test that showed a little promise was a psychological test of visual inspection time, as measured, if I remember correctly, by the Stroop test. But this was conterintuitive-- the (weak) correlation was negative (those who reacted fastest had lower IQ).

So what to make of this? I, for one, know jack about this area, so don't look at me.


Tuesday, February 21, 2006

Measuring Autistic IQ   posted by Jemima @ 2/21/2006 03:59:00 PM

ScienceNOW Daily News has an article on The Case of Mistaken IQ:

Health workers routinely assess autistics using a standard IQ test known as the Wechsler test. But this test requires that children understand oral commands, a trait that many autistic children have trouble with. Cognitive neuroscientist Laurent Mottron of the Hopital Riviere-des-Prairies, Montreal and colleagues noticed that autistic children did poorly on the verbal comprehension part of the Wechsler but exceedingly well on a part that tests non-verbal intelligence and reasoning.

So the researchers decided to test 30 autistic children and 30 autistic adults with a different IQ test called the Raven's Progressive Matrices test, which is written rather than oral. Healthy children and adults performed similarly on both the Wechsler and the Raven test. But speaking autistics scored up to 30 percentile points higher on the Raven test than the Wechsler test, the researchers reported here 19 February at the annual meeting for the American Association for the Advancement of Science (which publishes ScienceNOW). "Thirty percentile points could raise a retarded person to normal or a normal one to a superintelligent one," says Mottron.

It sounds like a bit of factor analysis could have gotten them the same result. I didn't find an actual reference, but here's the AAAS press release about the symposium.


Wednesday, February 01, 2006

A World of Difference: Richard Lynn Maps World Intelligence   posted by Jason Malloy @ 2/01/2006 07:12:00 PM

A review of Richard Lynn's Race Differences in Intelligence: An Evolutionary Analysis
(Click here for summary chart. Warning: 20 page review.)

The generally listed "peak" age for scientific creativity and productivity is around the surprisingly young age range of 30-40, but the same exact age doesn't apply to all scientific disciplines. The peak in fields that demand greater doses of pure reasoning, such as mathematics, theoretical physics, and molecular biology, appears to be somewhere in the twenties. So, for instance, James Watson discovered the double helix at 25 and then dropped off the radar as anything but a nerd celebrity. In contrast are fields such as evolutionary biology, where years of collecting and assimilating large amounts of data can be required for original analysis. So, for example, Charles Darwin was 50 years old when he published his landmark The Origin of Species, not to mention 62 for The Descent of Man and 63 for The Expression of the Emotions in Man and Animals. What's true for evo-bio may also be true for the often belittled field of psychometrics, or the measurement and analysis of human intelligence, and for much the same reasons. So, to take some more obvious examples, we find that John B. Carroll published his seminal work, Human Cognitive Abilities, at the age of 77, while Arthur Jensen was similarly 75 when he published The g Factor in 1998 (This spring, in fact, Jensen releases his treatise on mental chronometry, Clocking the Mind, at 83).

Richard Lynn, Professor Emeritus of Psychology at the University of Ulster, is surely another example. Now 76, Lynn has released a large number of papers and 5 books since his "retirement", 4 of them since 2001, starting with 1996's Dysgenics, 2001's follow-up Eugenics, 2001's The Science of Human Diversity, 2002's IQ & the Wealth of Nations, and now Race Differences in Intelligence. Richard Lynn appears to be a surprising exception as a modern hereditarian researcher who has not had to fight an exasperating battle with his institution, but his reputation in the media has been characterized by much the same turbulence as his colleagues' - most prominently during the Bell Curve backlash of the mid 1990s. Thus Leon Kamin's review of the book in Scientific American included:

I will not mince words. Lynn's distortions and misrepresentations of the data constitute a truly venomous racism, combined with scandalous disregard for scientific objectivity. But to anybody familiar with Lynn's work and background this comes as no surprise . . . It is a matter of shame and disgrace that two eminent social scientists . . . [would cite the work of] Richard Lynn . . .

Similarly, New Republic senior editor Charles Lane used Richard Lynn as his launching pad for two jeremiads against The Bell Curve in the invidiously titled (and argued) Neo-Nazis! published in The New Republic , and an expanded version of this article which appeared in The New York Review of Books, titled The Tainted Sources of The Bell Curve, featuring Lynn as the eponymous "tainted source". While these and similar articles in the popular press may have helped solidify Lynn's reputation as a "fringe" researcher among certain segments of the literate public, his reputation as a scientist in differential psychology remains secure and respectable. Little known, for instance, is the book review of Richard Lynn's Dysgenics (about the genotypic decline of socially valued traits) by the late scientific legend William Hamilton in the Annals of Human Genetics. This review is still available free at the journal's website as a tribute, because it was actually Hamilton's last published piece, submitted just two weeks before his tragically premature death in 2000. In comparison to Kamin's recriminations, Hamilton had nothing but good words for Lynn's character and work, calling Dysgenics a "brave and fertile book", and Lynn himself "brave, thick-skinned, and very persistent to swim against. . . popular antirealistic currents." and that "Lynn. . . does an excellent job with the facts". The contrast between interchangeable talking heads rebuking Lynn as a crank in popular magazines with Hamilton, possibly the most eminent evolutionary theorist of the 20th century, praising him in a prestigious journal at about the same time, could hardly be more ironic. (Meanwhile it is actually Kamin himself who can most convincingly be charged with data distortion and heavily compromised objectivity, see Mackintosh 1998 pp 78-79, 98-102)

Lynn's follow-up book Eugenics (about remedying the genotypic decline of socially valued traits) received similar praise in the American Psychological Association Review of Books (Lykken 2004) as "[an] excellent, scholarly book . . .one cannot reasonably disagree with him on any point unless one can find an argument he has not already refuted.", as well as by the journal Nature (Martin 2001) as a "comprehensive histor[y]" and a welcome one, "given the importance of the topic" of dysgenic trends. Lynn's third recent book, The Science of Human Diversity, a hagiography of the Pioneer Fund, also received supporting words in the APARoB from the psychologist Ulric Neisser (2004), who was also chairman of the APA's Taskforce on Intelligence (that was convened largely to counter the proliferation of scientific misinformation against IQ in the Bell Curve aftermath). Despite Neisser's repeated ostentatious and inappropriate insults against his hereditarian colleagues (such as saying that Lynn and Rushton's work on race "turns [his] stomach"), he ultimately couldn't avoid agreeing with Lynn's main argument: "Lynn's claim is exaggerated but not entirely without merit: "Over those 60 years, the research funded by Pioneer has helped change the face of social science"". Neisser tellingly concludes in agreement with Lynn (and against William Tucker's Pioneer book, also reviewed) that the world was actually better off having the Pioneer Fund: ". . . Lynn reminds us that Pioneer has sometimes sponsored useful research - research that otherwise might not have been done at all. By that reckoning, I would give it a weak plus" (These words coming from the APARoB should come as some news to certain 'watchdog' outfits which are still attempting to anathemize this same position. Pehaps all these journals and scientists mentioned above should now be added to the list of 'hate groups'?).

Lynn's fourth recent book, along with Tatu Vanhanen, IQ & the Wealth of Nations, received more mixed reviews in academic journals, but this should be taken as a sign of its controversial importance. Heredity, for instance, hedged its bets and printed a hostile review back to back with a sympathetic one (Richardson, Palareit 2004), as is sometimes done with controversial books (APARoB did the same thing for The Bell Curve, The Nurture Asumption, etc.). Unfortunately, much of the criticism in the journals, as is common in the popular press, centered around an obsessive focus with and antipathy towards the book's hereditary position on racial differences, far outstripping its relevance to the book's thesis that national IQ is a major cause of differences in national wealth. Worse still, many negative reviewers were deeply ignorant of the subjects that made them most angry. Some economists were outraged in stereotypical form, over use of the "discredited" IQ measure. Almost nobody was qualified to understand the race research, which Lynn specializes in, though it deeply unsettled almost all of them. So, for example, most reviewers took offense at the reference to race and brain size but none had informed or adequate scientific ways to critique it. To date though, the book is already generating a surprising amount of original commentary and research given this radioactivity, (Barber 2005; Dickerson, in press; Hunt & Williams, in press; Jones & Schneider, in press; Jones 2005; McDaniel & Whetzel, in press; Voracek 2004), and it is clearly Lynn's most important contribution to date. Also, while not referenced directly it is also influencing international policy. So, for instance, 2004's international panel of economists in league with Britain's Economist magazine, known as the "Copenhagen Consensus", ranked improving micronutrient levels as the second most important action to help the developing world. The impact of nutrition on intelligence was a prominent part of their argument, with 54 references to the word "cognitive" and 10 references to "IQ" (Jones 2005). These issues and recommendations are quite clearly taken from IQ & the Wealth of Nations.

While Lynn has made valuable and original contributions to a number of psychometric issues, IQ&tWoN, and his recent work with sex differences, confirms that group differences in intelligence are clearly his forte, and since so few other researchers dare to touch the issue, the field is mostly wide open for discovery. Which brings me to Lynn's fifth recent and latest book, Race Differences in Intelligence, which Lynn himself describes as ". . . the first fully comprehensive review that has ever been made of the evidence on race differences in intelligence worldwide". (p. 2) In contrast to IQ&tWoN, RDiI does not contain a newly created thesis. This is not to say it is unoriginal, many of its ideas (and much of its copious data) certainly originates with Lynn himself, but the theory, its basic outline and many of the key references of this book were almost all first presented 15 years ago in Lynn's Mankind Quarterly article 'Race Differences in Intelligence: A Global Perspective' and its companion piece 'The Evolution of Racial Differences in Intelligence', while an even more basic version appeared in his 1978 chapter 'Ethnic and Racial Differences in Intelligence, International Comparisons' in the book Human Variation.

The main strength of RDiI is just how much data Lynn has collected, totaling 620 different IQ studies from around the world and 813,778 tested individuals. While IQ&tWoN, published only a few years ago, presented data from 81 countries, RDil has boosted that number up to 100 different countries (additions include Cameroon, Central African Republic, Estonia, Iceland, Jordan, Kuwait, Laos, Lithuania, Madagascar, Malta, Mozambique, Pakistan, Samoa, Serbia, Sri Lanka, Syria, Yemen, and a few others), amounting to 137 newly referenced IQ studies. RDiI is seventeen chapters; the first 2 are on the concepts of race and intelligence. The next 10 chapters cover the psychometric data on 10 different racial groups: Europeans, Africans, Bushman and Pygmies, South Asians and North Africans, Southeast Asians, Australian Aborigines, Pacific Islanders, East Asians, Arctic Peoples, and Native Americans. The next chapter discusses the psychometric justifications for these results, while the last four chapters discuss the environmental and evolutionary nature of these differences according to Lynn's assessment.

Chapter 1 & 2: Intelligence and Race

These chapters are small and polemical. IQ&tWoN had a similarly abbreviated, but fully adequate chapter on IQ and I recommend that one instead. Lynn's chapter on race benefits less by squaring old scores with Ashley Montagu than it would by focusing more on the rapid advances in genetics. Lynn, for instance sourly demonstrates that Ashley Montagu and L.L. Cavalli-Sforza have continuously contradicted themselves trying to strategically deny that populations exist and are genetically differentiated even while ultimately admitting that they do. But these conceits ridicule themselves; Tan (2005) and Rosenberg (2002) , which both go sadly unreferenced, help illustrate and justify the use and meaning of Lynn's clusters far more than years-old absurd quotes from race-deniers, which are already well on their way to becoming little but historical oddities. On the other hand, Lynn can't be blamed that his book was published too late to catch the latest paper by Rosenberg in the December 05 issue of PLoS Genetics which again concludes, in the face of recent challenges stating otherwise, that:

. . . if enough markers are used with a sufficiently large worldwide sample, individuals can be partitioned into genetic clusters that match major geographic subdivisions of the globe. . .

Finally, as a tertiary complaint, Lynn also states:

In the 1830s, Samuel Morton (1849) in the United States assembled a collection of skulls, measured their volume, and calculated that Europeans had the largest brains followed by Chinese, Malays, and Native American Indians, while Africans and finally Australian Aborigines had the smallest brains. He concluded that these differences in brain size accounted for the race differences in intelligence.

This of course was also Stephen J. Gould's argument in Mismeasure of Man. Both mens' assertions should be read in light of science historian, William Stanton's more qualified judgment that: "Morton himself never equated cranial capacity with intelligence" (Stanton 1960, p. 30), and that Morton's collection was ethnographic in its aim.

Chapter 3: Europeans

Lynn first looked at European IQ in his 1978 chapter - it listed 14 studies from 13 different countries including the European repopulated territories of America, Australia, and New Zealand. Lynn found that they mostly scored extremely similar, with an average IQ of about 100. He also noted that results from Spain and Greece in Southern Europe were lower, although Italy was not. By 1991 the number of European countries covered was 23 with 35 studies. In comparison RDiI now lists data for 36 majority European countries, as well as data for European peoples in 6 mostly nonwhite nations, for a total of 112 different studies and a combined sample of 175,950 people. Since IQ&tWoN, much valuable new data from Europe especially comes from the recent book Culture and Children's Intelligence. The median IQ of European peoples is now listed as 99, and this mostly holds for rich countries in the North and poor ex-Communist ones in the East, as well as white Americans, Australians, etc., and whites in six different Latin American nations. But there also appear to be some differences too - Ireland, Portugal and Lithuania all have IQs, unlike their neighbors, in the low 90s. Multiple studies give similar results showing the scores are 'reliable' if not 'valid' (Ireland for instance has three studies with large standardization samples showing very similar results). Secondly, while Southern Europe does not score poorly as a block (Spain and Italy score "normally"), Southeast Europe does reflect a regional trend of lower scores that extends from the Balkans into Turkey and the Near East (so for instance Romania 94, Bulgaria 93, Croatia 90, Serbia 89, Greece 93 [5 studies], and Turkey 90). Lynn also compares 4 different regions of Europeans (including North America) on IQ and brain size, finding that North American whites have the largest brains and highest IQs (perhaps because of selective migration?) and Southeast Europeans the lowest test scores and brain size. Of course if there is a decline in the Balkans, Lynn's Flynn reduced estimate of 99 for Europe is incorrect, and needs to be dropped probably even a few more points.

While Lynn looks at adoption studies for evidence of heredity for other races, he unfortunately does not consider it for this major difference within Europe, even though it would seem like an even more suitable test, since these adoptees are not visibly racially distinct, controlling for the possible social effects of e.g., racism or stereotypes. Also, I know that there are, in fact, a number of IQ studies of Romanian children adopted into American and British homes. It was unfortunate that they were not reviewed. My superficial impression is that they indeed show a lower IQ than other adoptees.

I don't expect any of this to go uncontested, and Lynn's accuracy and care with the data is a fitful concern. Lynn and colleagues go back and forth over differences of up to 5 points in the technical literature all the time, and these debates are resolved slowly as more literature accumulates on the controversial/disputed difference, but no one has 'exposed' Lynn fraudulently manufacturing a conclusion, as is sometimes hinted. As with Africa, Asia, and sex differences, Lynn seems adept at building up the case for his controversial estimates with more data over time. But getting overly concerned with values of several points in single European countries is probably unwarranted, as Lynn himself notes, it's more helpful to concentrate on the general patterns.

Chapter 4: Africans

Lynn first looked at Sub-Saharan African IQ in his 1978 chapter - it listed 7 studies from 4 different countries including 1 Diaspora territory: Jamaica. By 1991 the number of African countries covered was 6 with 11 studies. In comparison RDiI now lists data for 23 majority black countries in and outside of Africa, as well as data for Diaspora blacks in 5 mostly nonblack nations, for a total of 155 different studies and a combined sample of 387,286 people.

References to the subject from the 60s and 70s typically gave Africans an IQ much like African Americans, thus Jensen (1973) wrote: "We do know that studies of the intelligence of Negroes in Africa have found them to average at least one sigma below Europeans on a variety of tests" (p. 66). Lynn (1978) is no exception. It wasn't until 1991, that Lynn had revised this estimate dramatically to minus 2 standard deviations, which has been the source of much anger and controversy ever since. Well, the current volume drops it a little bit lower even, to an IQ of 67 as the median score from 57 studies collected from 18 different African countries. Similarly, the average IQ of black populations from 6 locations in Latin America and the Caribbean is 71. This is virtually the same as the score for Ethiopians in Israel. In developed, predominately white countries, a second cluster of scores emerge for black Africans. African-Americans, of course, score about 85, while the median IQ from 20 studies of blacks in Britain is 86. Similarly, West Africans from the Dutch Antilles living in the Netherlands were found to have an IQ of 85. Although an older reference, Lynn also leaves out an IQ study of an established black population in Canada, descended from US migrants (Tanser 1939, 1941) - the measured IQ was about 87. Given that the scores have not changed a bit in America for 100 years, the age should not matter, and the educational gap of blacks in Canada is still discussed as a problem and mystery to this day.

More than Asia, Europe, and other areas of the world, the accuracy of such a low IQ for Africa is popularly questioned, but more with reflexive incredulity than adequate methodology. A typical comment is that it is hard to believe that half of Africa is mentally retarded. It is also hard to believe that 16% of African-Americans are "mentally retarded", but 16% of African-Americans do have IQs below 70, and the APA recognizes this as an accurate and factual reflection of ability - IQ tests are not biased against African-Americans (the criticism is fairly ignorant to begin with since diagnosing mental retardation is mostly orthogonal to the intelligence test, See Mackintosh 1998, p. 177). While this is not controversial now, among scientists, it certainly was as shocking to believe for many back in the 1970s as the 2 SD difference is to many today. While the logic of test bias has been around since at least the 1960s, a turning point in the scientific consensus on African-American IQ certainly came with Arthur Jensen's Bias in Mental Testing (1981) which exhaustively laid out the tools and methods for accurately discerning bias in IQ test results. In principle these same methods can be used to answer if 70 is or is not a spurious estimate for Africa.

Lynn unfortunately is less than thorough and rather unconscientious on this topic, and since the estimate was his to begin with he should be the most careful and aggressive one defending it. Lynn skips the issue of internal test validity entirely, even though there are some key references from Africa that stand repeating, and speak directly to commonly raised issues such as, e.g. language bias. Key references for external validity are also omitted, though Lynn's chapter 13 shows that IQ certainly doesn't underpredict African academic performance where countries are included for International comparisons. So for instance, while African countries like Nigeria and South Africa may score 2 SD below European nations on IQ tests, Lynn shows that international indices of math and science performance between the 1960s and 1990s reveal an even more dramatic gap of about 2 and a half SD. (It was noted in the Wall Street Journal, for example, that in South Africa: " . . . barely 1% of black high school students pass higher grade math"). Since East Asian nations score even higher than Europe, the gap approaches three standard deviations between Africa and Asia, consistent with earlier reports showing that there was almost no overlap between the highest and lowest scoring countries, e.g. TIMSS 2003 (PDF):

"Singaporean students had the highest average achievement at both grades, with their average eighth-grade performance exceeding performance at the 95th percentile in the lower-performing countries such as Botswana, Ghana, and South Africa."

Lynn also reviews data of so-called Elementary Cognitive Tasks from Africa, such as reaction time tests (how quick you process and react to a lit button on a console), and EEGs, which monitor how quickly the brain responds to a stimulus, confirming the general picture of African IQ. Jensen's upcoming book should have interesting things to say on this topic; a combined battery of ECTs correlate with IQ tests just as well as standard IQ tests correlate with each other (Detterman 1999), indicating that the pen and paper IQ test, as well as most attendant concerns about culturally biased tests, might very well become soon obsolete.

The issue of brain size is similar to that of test bias; I would think Lynn would want to up the arms race against his critics since this issue received so much attention in reviews of IQ&tWoN, despite being such a small and irrelevant part of that book. And yet brain size is prominently used to defend controversial hereditarian arguments in many chapters of this book, so it was unwise that key references are similarly omitted like with test bias. So, for instance, there is no discussion of the importance of, or tests for, a functional relationship between IQ and brain size, even though this is critical to the argument. And such research exists and would have made his argument much stronger and more immune to glib dismissal. Lynn does attempt to resolve one "contradiction" - that women have smaller brains but do just as well as men on IQ tests - by presenting data for his own theory that women actually average 5 IQ points below men. But since the difference between races is larger than the sex difference in IQ, and the brain size differences smaller, I don't see what has been resolved, even if we accept the still controversial sex difference in IQ.

Particularly interesting (not only for Africans, but for other racial groups reviewed as well) isn't just that racial groups score similarly on intelligence tests across an improbable number of different countries, but also have the same profiles (or "multiple intelligences" if you will) on these tests across nations as well. In the US, for instance, if we take poor and rich whites and look at their relative strengths and weaknesses on various test sections we will find the same pattern of strengths and weaknesses. Same for poor and rich US blacks, who have distinct strengths and weaknesses. African blacks show the same test profile as US and Jamaican blacks, for example with strengths on perceptual and short term memory tasks and weakness on tests of abstract reasoning (this is for matched total IQ, remember). The visuospatial profile that also distinguishes women and men and European and Asian/Amerindian populations has also long been noted by research of blacks in Africa and the United States, but this difference is not analyzed by Lynn.

For the first time I've seen, Lynn also reviews tests of "MQ" or musical intelligence for black and white Americans. While blacks score lower on almost all the items, commensurate with the fact that IQ correlates with musical ability, they also do much better, on average, than whites on rhythm items - Lynn calculates a rhythm IQ for Af-Ams of 106, though no cross-cultural results are presented, this has been recognized in a number of societies through time. Since Sub-Saharan Africans have been musical innovators across a number of different countries, this topic should have more attention.

Based on the IQs of transracially adopted black children, Lynn decides that the 1 SD IQ difference of American blacks (same as in Britain and the Netherlands) is 100% genetic, given the lack of any convincing environmental theory or data for the gap. Based on this he decides that poor nutrition primarily is depressing the African (and mostly identical black Latin-American/Caribbean) IQ about 13 points. Indeed, incredulity that African IQ could be any lower than African-American IQ is belied by known drastic comparative disadvantages of Africans on variables known to affect IQ. These include things such as higher lead exposure (which can lead to IQ reductions of 4-7 points) and micronutrient deprivation, such as iodine deficiency (reductions of 10 points). Indeed, critics are incredulous over the wrong gap! - after all, it is the 15 points between American blacks and whites that is hard to account for, not the 15 points between American blacks and Africans. 5 additional IQ points between African-Americans and African-Africans, Lynn attributes to the white admixture of American blacks. Lynn puts the level of white admixture in African-Americans at 25% based on references from 1971 and 1992, and northern black admixture at 50% (based on pure conjecture) and concludes from IQ studies that African-Americans gain 1 IQ point for every 5% of white admixture. Lynn's estimate is compromised because his admixture references are outdated and his estimate of northern admixture is contradicted by the data. Parra et al. (1998) put the latest estimate of average admixture at 17%, not 25%, and don't even find admixture higher than 23% in any sampled US region. It's difficult to guess why he is using the obsolete reference, when he himself has previously cited the Parra paper and the 17% estimate (Lynn 2002).

On a final note, I will say that Lynn is especially talented at bringing new references to the table, so that while his 1991 report featured only three references of black IQ in Britain, this book delivers 20 - all in support of a black IQ in Britain typically much lower than all other ethnic groups, and much like that of blacks in the US. This is no small ability since critics are terrible at knowing or caring about the literature. But more important is this - Lynn should expand his research ability to cover a broader range of data points. An over-reliance on IQ tends to minimize just how strong these international racial patterns are because it limits the argument to just one kind of data. A book like Lynn's, in my opinion, would be much more effective if it started with the race and worked up to the IQ data, where available, instead of vice versa. So for instance, a more thorough picture would be available of racial patterns if, instead of cataloguing nations where we have black IQ, we first catalogue nations that have blacks, and chart what we know about their comparative situation in each country up from that fact, given whatever data is available, be it IQ or educational or economic data - or even anecdotal (journalism/anthropology) reports or local viewpoints, if that is all that's available. The point is that IQ data is limited and working up to the data from the people would make the patterns even more unavoidable. I have in mind the structure of Thomas Sowell's Migrations and Cultures or Amy Chua's World on Fire which didn't even use IQ data, but demonstrated ethnic patterns through economic, political, and educational data. A merge of style and data between these books and Lynn's would paint an even more persuasive picture of the differences that do, more or less, rather reliably follow race, and perhaps uncover which ones don't as well.

Chapter 5: Bushmen and Pygmies

In Frank Miele and Vincent Sarich's Race, an account is given by Henry Harpending of a resourceful young Bushman who repaired his Jeep by jumpstarting it with a rope, like a lawnmower. Harpending and his colleagues concluded that Bushmen were smarter than other Africans: "All of us have the impression that Bushmen are really quick and clever and are quite different than their neighbors . . . I expect there will soon be real data available from the Namibia school system" (p. 227). On the other hand, Lynn lists the average IQ of Bushmen, estimated from 3 studies, as 54! Lynn decides that this is a reasonable score by considering that it is equivalent to the average score of an American third-grader: " An IQ of 54 represents the mental age of the average European 8-year-old child, and the average European 8-year-old can read, write, and do arithmetic and would have no difficulty in learning and performing the activities of gathering foods and hunting carried out by the San Bushmen" (p 76). Lynn's estimate is not new, the same studies and same average IQ were listed in the 1978 chapter, the only thing that has changed is Lynn's opinion, who then wrote: ". . . it strains one's credulity that a population could long survive the rigors of the Kalahari with a true mean IQ around 55". This should not serve as a "gotcha", because I agree that the 'age' comparison is more appropriate than the 'mentally retarded' comparison for thinking about lower IQ population (such as the 16% of Af-Ams who score below 70). At the same time this also demonstrates a theoretical deficit in intelligence research of distinguishing exactly how an average child with an age unadjusted IQ of 63, a below-average non-retarded adult with an IQ of 63 and a mentally retarded adult with an IQ of 63 all differ in what are fairly considered intellectual abilities (real world indicators of independent self care and adjustment). Suggestions that these are just "personality' differences are rather specious, especially when Lynn gets to the point of comparing young children and apes as well as humans and extinct hominids on the same linear IQ dimensions. Although I agree that test bias literature also confirms important aspects of intelligence are being captured across diverse groups.

Lynn notes there was a Pygmy intelligence study, but says that it does not permit an average IQ, though he does suggest it is lower than other Africans. Since no new data has been collected for Pygmies and Bushmen in over thirty years, these assessments are dead ends. As one caveat, I have to object to Lynn's statement that " Pygmy children up to the age of puberty have normal height, but when they become adolescents they do not have the growth spurt of other peoples because of their low output of the insulin-like growth factor 1" (p. 77). This fact is outdated, a mixed longitudinal study from 1991 found that Pygmies were much smaller than other populations at birth and up until age 5, indicating a suite of adaptations for smaller size.

Chapter 6: Near East and South Asia

Lynn first looked at the Middle-East/South Asia region in his 1978 chapter - it listed 5 studies from Iraq, Iran and India and an average of 86 was given. Except for one study for India, this region was not addressed in the 1991 review. RDiI is pretty much the only survey of Middle Eastern IQ to date, now listing data from 15 predominately West/South Asian countries as well as data on these populations living in European countries for a total of 98 studies and a combined sample of 65,855. The median IQ is 84. 40 studies are also given for South Asians living in a variety of African, Asian and European countries - the median IQ for Indians in India is listed as 82, in South Africa as 86, and in Britain as 89. South Asian Americans have not been tested to my knowledge, but data from income and education indicate they probably have IQs significantly higher than average - this is likely due to selective top-tier migration. Unfortunately, no data for IQ diversity within India is discussed, even though some data probably exists right now and probably contains some fascinating information on caste and ethnic differences. In my opinion South Asia (the Indian subcontinent) should have been a chapter apart from West Asia (the Middle east), highlighted more by the fact that Lynn also lists a score of 89 for the Near East and 82 for South Asia, suggesting the 84 score is misleading.

Lynn argues for a partially environmental explanation for lower West/South Asian IQ with reference to nutrition as he does with other regions, but argues that since these populations perform much lower even in Western nations and have a lower brain size, that there are genetic causes too, which in his evolutionary framework is said due to their more limited exposure to two little Ice ages than Europeans and East Asians. Lynn leaves out an important genetic issue as well, one mediated by cultural events. While the prevalence of cousin marriage is less than 1% in Europe and its Diaspora nations, and low in much of Eastern Asia as well, the Middle East has the highest rates of inbreeding in the world, running to 20-50% of all marriages (see the work of Alan Bittles for more). Jensen (1998, p. 194) lists 14 studies of inbreeding depression on IQ, many of them done directly within the Middle East, and finds the typical cost of cousin marriage is 7-8 IQ points. It is doubtful that this is a major source of the average IQ difference between Europe and the Middle-East, though, since all, or even a majority of, the people of this region do not engage in cousin marriage, making the real effect, at maximum, only a few IQ points. Also most of South Asia, which has much less inbreeding, does not appear any higher.

While Lynn's book lists the IQs of blacks, Asians, Indians, and other groups living as internationally dispersed minorities, this is not done for Ashkenazi Jews, who are largely - sadly -neglected, though a few examples are given to indicate they score highly in America and Britain. Earlier discussions of Israel's IQ, when it was listed as 94 in IQ&tWoN treated it as a suspect score, because Ashkenazi Jews are thought to score 1 SD higher than other Europeans. Of course even if this were true (and Lynn himself (2004) estimates the IQ as only about 107), Ashkenazi Jews represent only about 40% of Israel's population, and Oriental Jews and Arabs, who make up the majority, are thought to score nearly as far (if not more) below Europeans as Ashkenazi Jews score above them, so the estimate actually wasn't unreasonable at all (although '95' in a country with a distinct, high scoring population is qualitatively different than a '95' country with a single bell curve). Lynn lists 8 studies for Israel with IQs ranging between 89 and 97 and with a median of 95, but none of the studies are broken down by ethnic background to provide direct estimates of the IQs of Oriental and Ashkenazi Jews. So Lynn uses population percentages (40% Ashkenazi, 40% Oriental, 20% Arab), results from one direct study of Israeli Arab IQ (86), and knowledge from several Israeli studies that indicate that Ashkenazi Jews score 12 points higher than Oriental Jews, to give indirect weighted estimates of 91 for the IQ of Oriental Jews and 103 for Ashkenazi Jews in Israel. No direct studies are given or listed for these groups in Israel, and if Lynn is correct that Jewish-American IQs are really only about 107, then that really isn't different enough from his Israel estimate, in my opinion, that we can rule out their scores being identical in each nation - the estimate just isn't that precise. Another puzzle left untouched is that the listed Oriental Jewish IQ is also 3-7 points above the regional average. Is it possible that for reasons of cultural and/or genetic amalgamation, the two populations are meeting each other in the middle; one being pulled up and the other being pulled down? Lynn does believe Ashkenazi Jews have some genes related to higher intelligence, which he attributes to medieval persecution. At his book's cost, Lynn makes absolutely no mention of Gregory Cochran and Henry Harpending's Ashkenazi paper at this point, which I find curious.

Chapter 8: Australian Aborigines

Lynn first looked at the Australian Aborigines in his 1978 chapter - it listed 3 studies, and he estimated their intelligence, much like Sub-Saharan Africans, as 85. In 1991 the same three studies were listed, and there is no suggestion Lynn lowered his estimate. When Ed Miller examined studies of Australoid intelligence in 1996, he too suggested something like 85. In comparison RDiI now lists data from 29 studies of Australoid populations, including those of New Guinea for a combined sample of 4,785. Since that time Lynn has dropped the Australoid IQ average a dramatic 23 points, down to 62. This is considerably lower than all previous estimates have suggested, but Lynn's review also highlights just how neglected this populations intelligence has been, even by Lynn, until now. Small admixture and adoption studies exist for Australian Aborigine intelligence and both suggest something hereditary. These populations have had some of the lowest technological development of all populations and also have the smallest brains of any living population. An exception is the visual parts of the cortex, which are much larger than in Europeans. Interesting given their much lower intelligence, then, that their visual memory abilities are substantially superior - one researcher found a visual memory IQ of 119. Genetics are further suggested because the advantage is also true for very young children and for aborigines born into modern urban settings.

Jared Diamond famously stated that he believes the populations of New Guinea to be more intelligent, on average, than Europeans. The median of 5 intelligence studies in New Guinea is reported as 63, no different than Australian Aborigines. It seems that if what Diamond asserts is true, at the very least children from this stock raised in white homes should be able to, on average, reason through a Piagetian conservation of water volume problem as well or better than their environmental siblings, which is not what we find.

Lynn offers the opinion that the Australoids have lower intelligence than Africans because their population numbers were lower, and thus less likely to accrue advantageous chance alleles (he applies this theory to a number of other populations, such as the Mongolians, Eskimos, Polynesians and Amerindians). The rate at which these genes could spread is interesting in the light of Bruce Lahn's ASPM and MCPH1 (also unmentioned!), which may be related to cognitive function, rising to high frequency among these populations but not among Africans. Especially the more recent ASPM, whose range across the entire span of Eurasia in 6000 years does not agree with Lynn's estimate that an advantageous allele would spread only 800 miles per 25,000 years (p 222). Also interesting, if these alleles are related to increased brain size (possible, though yet to be demonstrated), that they exist in such high frequency in these populations.

Chapter 9: Pacific Islanders

As with the Middle East, Southeast Asia and Australoids, very little has been written to summarize the intelligence in Polynesian regions before this book. RDiI reviews 29 studies and a total sample of 7729 from the Pacific Islands.

In his 1938 book, Heredity and Politics, written largely as a riposte to the noxious racial politics of Nazi Germany, J.B.S. Haldane devoted two chapters to what evolutionary biology, or more specifically the Neo-Darwinian Synthesis, implies for racial differences in man. Much of what he says is level-headed. On the issue of race and intelligence, Haldane specifically compares the ability of Pacific Maoris with that of Australoids. For instance he cites Maui Pomare, a Maori who had actually for a time served as Prime Minister of New Zealand:

We cannot, I think, deny a very considerable difference in the behaviour of the Maoris and the Australian black-fellow, and we can ask whether it is due to nature or nurture? That is an exceedingly difficult question to answer. But I find it very hard to rule out nature. (p. 141)

Haldane's assessment of ability finds support in intelligence tests. By world standards, Maori are bright, and perform much higher than Australoids. The median IQ of 15 studies of Maori from New Zealand is 90. This is probably higher than other Polynesians, as the median IQ of 14 additional studies from 6 non-Maori Polynesian territories is 85.

Chapters 7 and 10: Southeast Asians and East Asians

Starting in the late 1970s with Singapore and Japan, Richard Lynn discovered that East Asian countries obtained higher scores on IQ tests than the Western populations these tests were standardized on (See the picture from the 1982 Discover Magazine cover story on Lynn's findings here). In 1978 he reviewed 5 studies from Singapore, Japan, and Taiwan. It wasn't then expressly stated that East Asians had higher IQs, although Lynn noted that the result of 107 for Japan "appears to be the highest mean IQ ever recorded for a national population". By 1991 Lynn had raised his number of studies to 15 from 4 countries, and integrated it into his climactic evolutionary theory to argue that East Asians had evolved higher intelligence than Europeans, with a mean IQ of about 106. A number of notable critiques of Lynn emerged in the academic realm since his first studies in the 70s, including an early charge by Stevenson and Azuma (1983) that Lynn's Japanese IQs were inflated by socioeconomic and urban bias. Stevenson (1984) cast further doubt on Lynn by conducting a large international IQ study of his own, finding equal scores between a group of Chinese, Japanese, and Minnesotan elementary school kids. Finally, in Asian Americans: Achievement beyond IQ (1991), unusually principled hereditarian challenger James Flynn reanalyzed 100 years of IQ scores of North American Asians, which scholars had previously judged to average about 106. Although Flynn agreed with Lynn that IQs in Japan were higher than in America, he argued that earlier American studies were uncorrected for the secular increase in intelligence (the Flynn Effect), artificially inflating Asian-American IQs. In other studies, he argued, the Asian samples were not representative. Flynn re-estimated Asian-American IQ down to 98. All of these critiques (save aspects of Flynn's) didn't have much to stand on, even at the time they were leveled, much less now when the contrary data has grown exponentially. For instance, in a response to Stevenson and Azuma (printed on the same page as their critique) Lynn (1983) adjusted for the problematic demographic factors and found most of the difference was retained. As for Stevenson's study that found no difference, this is not surprising since Minnesota whites score higher than any other US region, with scores identical to Lynn's average for East Asia. And of course these same Asian countries with higher IQ scores also score higher on international records of math and science achievement than Western countries (see review of 'test validity' chapter below - these measures are almost perfectly correlated with IQ). As for Flynn, Flynn's results only applied to the pre-1980's - several studies from after that (coincidentally?) showed IQs much like what had previously been reported.

Whatever the merit of these previous challenges, Lynn has clearly upped the ante in Race Differences in Intelligence in defense of his argument of higher East Asian IQ. Lynn now presents 101 different studies of East Asians and a combined sample of 128,322, giving an average IQ of 105. From 5 different Asian countries alone (China, Japan, S. Korea, Singapore, Taiwan), we are presented with 59 studies - 4 times as many studies from East Asia as Lynn presented in 1991. 34 of these new just since IQ&tWoN! The median IQ from these studies is 105. In responses to Flynn's earlier book, Lynn reanalyzes 27 studies of Asian-American IQ. In contrast to Flynn's 98, Lynn finds a slightly higher average IQ of 101 for Asian-Americans, from 9 studies previous to 1950 (consistent with their higher academic and professional accomplishments at that time). For 9 studies since 1950, Lynn finds an IQ of 104, virtually identical to countries in East Asia. Additional studies show similar East Asian IQ in Canada, Britain, the Netherlands, Brazil, and Malaysia. Though educational and economic data not included in the book would paint a similar picture in over a dozen other countries from Jamaica to Russia.

In defense of a hereditary explanation, Lynn presents data from 4 studies of East Asians adopted into white homes, showing higher IQ scores. In fact here the data is even stronger than what Lynn presents - more IQ studies exist than what he presents, as well as other supporting evidence. In a month or two on GNXP I will present the first comprehensive investigation of international transracial adoption literature (a large expansion off this post), presenting much data not included in RDiI, particularly for East Asians.

Lynn also included an earlier chapter on Southeast Asians, but given an issue with their relationship with East Asians I've decided to review them together. The only native country from Southeast Asia to appear in 1978 was Indonesia, and, like the Middle-East, little data existed for this region until IQ&tWoN. RFiI lists data for 6 Southeast Asian countries in 18 studies for Southeast Asians living both in Asia and abroad for a total sample of 13,433. The median IQ is listed as 87. It is suggested based on brain size and scores abroad that these scores are partly genetic. As with the other chapters, Lynn justifies his racial division of East and Southeast Asia by reference of L.L. Cavalli-Sforza's History and Geography of Human Genes, but Lynn does not order his countries how they should be arranged according to this reference. This book tells us that South China lumps closer genetically with Southeast Asia than North China: " Northern and southern Chinese are substantially different genetically" (p 100); ". . . the South Chinese . . . are more closely related to Southeast Asia than to Northeast Asia" (p 229). This is significant because many of the high IQ scores Lynn places in the 'East Asian' chapter are from various South Chinese populations, such as the Hong Kong studies, as well as much of the over-seas Chinese scores from America and Southeast Asia. This creates a potential problem for a genetic theory of either East Asian high ability or Southeast Asian low ability, as noted by Ed Miller over ten years ago:

The importance of this finding of a relatively large difference between the North and South Chinese is that much research is done on American or Canadian born Chinese (Vernon, 1982), which are predominantly of South Chinese descent, coming from Hong Kong, Canton, or their vicinity. It may be risky to generalize from this to the whole of Han China.

For those interested in behavior and economic development, the resemblance between South Chinese and the Filipinos, Malays, etc. presents a problem. The South Chinese generally do well on intelligence and academic tests whether tested in the US or in Hong Kong, often better than Caucasoids. Filipinos generally don't do as well. Within Malaysia, the Chinese test much better than the Malays. Within Southeast Asia, the overseas Chinese generally do much better economically than the Malays (Sowell 1994). Thus, it is surprising to see the small genetic differences between the South Chinese and adjacent populations.

In a related criticism, one of the adoption studies that Lynn uses to support a higher genetic East Asian IQ, (Clark & Hanisee 1982) is actually mostly comprised of Southeast Asians, about half the sample being Vietnamese. Lynn resolves this by asserting that most of the Vietnamese in this sample were actually Chinese-Vietnamese, but I see nothing in the original paper to indicate this, and since most of the higher achieving overseas Chinese in Southeast Asia are from the Southeast Asia genetic cluster anyways, I hardly see how this resolves anything. While one might posit a cline in IQ scores (and scores do seem to drop off from Thailand into Malaysia), the South Chinese show absolutely no deficit in ability or differentiated profile from East Asians. This makes an interesting contrast between Southeast Europe and the Middle-East where we see a cline in ability follow a genetic cline across a stark cultural boundary, suggesting genetics. Instead here we have another cline in genetics, but a stark difference in ability following a stark cultural boundary, suggesting environment. This might mean that underperforming Southeast Asian-American groups, such as the Hmong, have hidden potential after all. Then again, selection could have occurred in China independently for this trait, long after the formation of the races, but modern selection and subracial populations are at odds with the theoretical structure of this book. Likely much more data is required before simplified assumptions and approaches can relax.

Finally, at the risk of being too trivial in my criticisms (which I offer in benign spirit), Lynn asserts " Only one study has been published on the heritability of intelligence in East Asians (Lynn and Hattori, 1990)" (p. 145), citing his own study from Japan. This is not correct. In the International Handbook of Intelligence, a group of Japanese psychologists write: "Since the beginning of the history of psychology in Japan the issue of the heredity of intelligence has been a major focus of inquiry. We can find a notable twin study in the very first volume of The Japanese Journal of Psychology" (pp. 310-311), and they go on to discuss several studies of heritability from Japan published in both American and Japanese journals stretching back to early in the 20th century.

Chapter 11: Arctic Peoples

The general consensus among the few scholars interested has long been that arctic groups, though living 'primitive' hunter-gatherer life-styles (much like some of the other extremely low-scoring groups reviewed here) do unusually well at IQ-type tests - in fact not much different than Europeans. The earliest discussion of Eskimo intelligence that I know of (incidentally, not cited by Lynn) is in Robert Marshall's Arctic Village (1933). Marshall gave all the Eskimo children in the small settlement town of Wiseman, Alaska the Stanford-Binet, and found them to outscore the American norms. Marshall commented that the ". . ..startling record shows these little Eskimos to far better advantage than normal American white children" (p. 79). Of course by that point the record was very small: Florence Goodenough found similar results with her Draw-a-man tests on a handful of other children, and Marshall discusses several other tests showing similar performance but does not clarify if this was his sample or another. With the advantage of 40 more years of data, John W. Berry (1971) indicated this view had not changed in his review of studies of Eskimo intelligence in the 1970s:

Probably the most interesting consistent finding is that Eskimos differ very little from [white] norms on tests involving perceptual skills or those abilities tapped by "perfornance scales" of conventional intelligence tests. It is often found, of course, that non-western peoples (e.g. in Africa and among American minority groups) perform significantly lower on these tests, and so this northern result is in many respects a unique finding.

Richard Lynn appears to be the first person to challenge this in his 1978 review, where he argued that one of Berry's studies actually showed an IQ in the 80s instead of 100, due to an inappropriate age comparison. He also presented one more study showing a score in the 80s, although he allowed that another study did show comparable scores. RDiI, in contrast, includes 15 studies of Arctic populations and a total sample of 2,690 people. Lynn concludes that they are the (distant) third most intelligent racial group reviewed, with an average IQ of 91.

Even in Marshall's book there is discussion of the Eskimos ability to draw detailed maps from memory. Like the Australian Aborigines, with whom they share a recent hunter-gatherer lifestyle, Lynn shows the Arctic people have an elevated visual memory IQ of 106. Although it is not shown that this likewise present in Eskimos removed from the hunter-gatherer lifestyle, it is also a feature shared by related groups such as East Asians and Native Americans.

Chapter 12: Amerindians

Several studies of Native American intelligence were discussed by Lynn (1978), though no exact average was given. By 1991, 15 studies of North American Indians groups were discussed and a median IQ of 89 was provided. In contrast, RDiI now discusses 63 studies of Amerindians with a total sample of 37,304. For 21 studies of North American Indian groups Lynn finds a median IQ of 86, and for 11 studies of Latin American Indian groups across five different countries, Lynn finds a median IQ of 86. Additionally, 20 studies of (mostly mixed race) Hispanic Americans reveal a median IQ of 89, identical to the meta-analysis by Roth (2001). Small hybrid and adoption studies are also presented.

In World on Fire Amy Chua describes the relationship between economic status and "Indian-blood" throughout Latin America: "Latin American society is fundamentally pigmentocratic: characterized by a social spectrum with taller, lighter-skinned, European-blooded elites at one end; shorter, darker, Indian-blooded masses at the other end . . ." (p 57). As an example she describes her experience in Mexico:

Almost without exception the Mexican officials, lawyers, and business executives we dealt with were light-skinned and foreign educated, with elegant European names. Meanwhile, the people doing the photocopying and cleaning the floors were all shorter, darker, and plainly more "Indian- blooded." While considerable social fluidity exists in Mexico, it is also true that lightness of skin correlates directly and glaringly with increasing wealth and social status. (p 59)

The trends Chua observes within Latin American countries also appear to operate between these countries, with countries with mostly European populations, like Chile and Uruguay, being the most economically developed and countries with largely Amerindian populations, such as Bolivia and Ecuador being the least economically developed. Coblogger emeritus Godless Capitalist once compared 12 South American countries and found a correlation of .96 between GDP-per-capita and percentage of the population that is white.

Lynn's data confirms this general picture with intelligence as well. Both with between country differences (e.g. Uruguay (96) and Chile (99) score like European countries, while Ecuador's IQ scores range within the 80s), and within country differences; to use Chua's Mexico as an example, last year Lynn tested a representative sample of 920 in Mexico with the Standard Progressive Matrices and found that whites had an IQ of 98, Mestizo (mixed race) 94, and Native Indians 83 - all compatible with Chua's observations of a "spectrum" of "social status" by amount of "Indian-blood".

Chapter 13: Validity and Reliability

I covered some of this topic prematurely in the Africa section, but this chapter deals with the appropriateness and accuracy of these cross-cultural IQ results. 'Reliability', in this case, is how replicable an IQ score is within each nation - telling us if a score is capturing something that can be fairly generalized. Despite the Flynn Effect, reliability is very high. If a nation is tested a second time or third time, the second and third score will look much like the first one - the cross-cultural reliability of the scores is .94. As an example, I noted last year that a 1997 test of almost 4000 Thai children (not included in RDiI) found an IQ the same as the only earlier result from Thailand, a much smaller sample from 1989. Evidently Thailand has an IQ about 8 points lower than the West. The second question though is if the replicable score reflects a replicable ability or just a replicable test score - is 92 an unfair reflection of Thai ability? That isn't to say, "is it permanent or genetic", just "is current performance in other domains in agreement with the measurement". 'Validity', in this case, is if an IQ score predicts the same real world outcomes for one population as it does the reference population. For this Lynn looks at five data sets of international math and science performance, which span 30 years (Other IQ researchers have started matching up national scores with these data sets as well; Hunt & Wittman, in press). All the data sets correlate with the IQ measurements from .8 to .9, and Lynn even suggests that correction for attenuation gives them a perfect relationship. Typically the differences appear even larger on these scholastic measures than they do on the IQ measures, so while the difference in IQ between East Asian and European countries is about 0.33, or a third of a standard deviation higher, their achievement scores are 0.44 higher. And while Africa falls 2 SD lower in IQ, math and science achievement scores taken from West Africa, East Africa, and Southern Africa are 2.44 SD lower than European nations. These scores are, of course, related to national wealth as well, as demonstrated in IQ & the Wealth of Nations, where the correlation between IQ and economic development was .73. Lynn doesn't mention that Jones & Schneider (in press) also found IQ to be the best international measure of economic human capital, better than all educational variables, all but a single one of which didn't even pass a significance test for GDP growth between 1960 to 1992. Lynn gives a correlation of .51 between IQ and GDP growth between 1950 to 1990. The IQs were high before many of the rich countries got rich, suggesting a cause not a consequence of growth (Jones 2005). Jared Diamond (2004), quite inadvertently, illustrates the consequences of economists ignoring intelligence with this quote:

". . . around 1950, when South Korea, Ghana and the Philippines were equally poor, most economists predicted that resource-rich Ghana and the Philippines were on the verge of wealth, whereas South Korea was doomed to remain mired in poverty. The result, of course, has been the opposite . . ."

Chapter 14: Genes and Environment

While genes may have been mostly irrelevant to the main arguments of IQ&tWoN, the same could hardly be said about this book where genetics are freely stressed. This chapter again reviews the evidence for genetics, including that the same patterns reappear across numerous nations, admixture and adoption studies. But here Lynn also covers what aspects of the environment are likely causing racial differences too, which Lynn is able to do with more accuracy and sophistication than critics who are more concerned with protecting taboos than figuring out sociological puzzles. Many of the popular and politically acceptable "answers" such as aspects of the shared family and education fail direct and adequately controlled tests (Lynn does believe education has an important impact on achievement, if not intelligence, and has written a book on this topic, which was also adapted into a National Review cover story). Lynn focuses here on his own hypothesis - nutrition. Before any other psychologist Lynn (1990) had proposed and supported the hypothesis that nutrition is responsible for the Flynn Effect. He has also demonstrated previously why it the best supported environmental explanation for certain racial differences. In this chapter Lynn compares NGO reports of four different signs of severe malnutrition - underweight, anemia, wasting, and stunting - for five developing regions. This shows that Latin America suffers the least malnutrition, followed by the Middle-east, Asia/Pacific, Africa, and finally South Asia, which suffers the worst malnutrition of any region. Lynn decides half the African deficit is due to malnutrition, but that it can't account for any of the American gap, where blacks show no other physical signs of malnutrition. But here Lynn doesn't mention breast-feeding, which as Arthur Jensen has shown (1998, pp 506-507) is practiced almost three times as much among white Americans than African-Americans and has been associated with IQ gains of nearly 10 points. It is likely that effectively encouraging breast-feeding would have a positive impact on the next generation of African-Americans.

Chapter 15-17: Climate, Brain size, Intelligence and Evolution

These three, closely related last chapters, which begin with a summary of the work and theories of Harry Jerison, regarding intelligence, evolution and brain size, cover Lynn's evolutionary theory of racial differences. As with most evolutionary psychology, as well as evolutionary anthropology of humans, the theory and its assumptions will remain controversial. Lynn's main agent of racial differences in intelligence is relative exposure to two recent ice ages, one 77,000-50,000 years ago, and another, more severe one 28,000-10,000 years ago, which he argues increased the intelligence of Europeans and East Asians significantly above other world populations.

But is this theory plausible? Well, let's ask that with several more specific questions, a) Does intelligence follow a pattern consistent with this theory? b) Do the differences look genetic?, and c) Is there evidence to suggest this evolutionary pressure?

As to the first question, the answer has long been regarded as 'yes'. It has been noted since the 18th century that the more wealthy regions existed in the temperate regions with the poorer regions in the tropics/subtropics, something that economists and sociologists have also considered during the 20th century (see also David Landes). Evidence used to support Lynn's theory, is often just indirect ways of restating this same fact. So for instance the upcoming paper by Templer & Arikawa (in press) is presented as evidence which finds that national IQ is strongly related to lowest national winter temperature, -.69, and that skin pigmentation (mostly a record of evolutionary latitude according to recent evidence) has a very strong correlation with intelligence, .92. These relationships hold within and between continents. The most notable example of this, though, is brain size. With several minor reversals, the 10 populations in Lynn's book, stack almost in the exact same order on brain size as they do with IQ. Most people, even so-called "scientists", deal with this uncomfortable fact by simply denying any association between brain size and intelligence, either in humans or across the evolutionary record, something clearly and overwhelmingly contradicted, in both cases, by the scientific evidence. The same folks, interestingly, often hedge their bets by also denying any race differences in brain size. This too has turned more and more desperate as the studies pile up. The same folks, interestingly, often hedge their bets by also saying the differences, which don't matter and don't exist, are probably not genetic. Since this is not likely either, the most scientific objection (compatible with these three well supported premises) is that the race differences in brain size are just yet another way of stating that high IQ/wealthy populations occupy the temperate zones and low IQ/poor populations, the tropics/subtropics. Bergmann's rule states that animals in colder climates tend to be larger and rounder to conserve body heat, while ones in warmer conditions smaller and thinner to help shed excess heat more efficiently. On the one hand while this may be true for the heads of our races, it isn't exactly true for the bodies, as head and body measurement data from the US shows that East Asians have much larger heads than African-Americans, but smaller, thinner bodies (Rushton 1997), which complicates the Bergmann explanation. In other words East Asians and Europeans don't just have larger heads, they have larger Encephalization quotients (EQs), or brain size controlling for body size - which also tracks changes in intelligence across the evolutionary record, so Rhesus monkeys have an EQ of 2.10, chimps 2.60, Australopithecus 3.70, Homo habilis 4.30, Homo erectus 5.00, and the average modern human 7.5 (while average IQ of modern humans = 90). Before the second most recent ice age, Lynn reports, the Europeans had an EQ of 7.3, which had inflated to 8.1 by the end. So apparently current differences in EQ between human populations are comparable to differences between species, which also correlate with transfer index scores and performance on other animal intelligence tests.(e.g. chimpanzees outscore rhesus monkeys). Unfortunately, Lynn does not help disentangle possible confounding between climate and intelligence by calculating EQs for the various groups, or detail if these scores are different from the raw sizes. And it matters for the evidence that suggests climate instead of intelligence. For instance, the head sizes continue to increase with latitude, while intelligence does not; the largest human head sizes of all are at the frigid southern tip of Tierra del Fuego and among the arctic populations such as the Eskimos. Interestingly here, Lynn may have undermined one of the best possible evidences for his theory, even if not completely. After all, scientists had long thought that the arctic group was the only group living a 'primitive' lifestyle that scored anywhere close to (much less the same as) white European populations on IQ tests. Lynn is the first one to dispute and revise the Eskimo score as such, down to 91, even though he is the biggest proponent of cold increasing intelligence. Still, though, the actual IQs of Eskimos and related groups still support Lynn's theory as much as they undermine it, as they are still the third highest scoring population on earth behind Asians and Europeans (even if they cluster with the other populations). Even if northern brain sizes are entirely due to climate instead of selection for intelligence, it's possible that, while other neurophysiological processes can modify intelligence independent of brain size (and Lynn puts this at some 75% of existing differences), increased intelligence in some measure is a likely by-product of brain expansion, given their intimate developmental associations. This is still consistent with what we find with larger-brained, higher IQ northern latitude populations. Interestingly the pattern may be even more consistent with Lynn's theory than he himself recognizes. Take Amerindians - Lynn argues (pp 242-243) that North American Indians should have higher intelligence than South American Indians due to greater exposure to the second ice age, but he also decides that both groups have an IQ of 86. But this is due to Lynn's method of taking the median, which doesn't always appear to be the best average. It gives equal importance to throw-away studies with 20-30 people and demographically controlled standardization samples with 1 and 2 thousand people. Lynn's number of 86 for North American Indians, for instance, is significantly lower than what was found by the largest study yet of Amerindian intelligence - the Coleman Report, which tested nearly 5000 Native-Americans and found an IQ about a half a standard deviation above African-Americans. When we take the weighted average of all the American groups, using the numbers in Lynn's book, we get an IQ of 90 for the Arctic people, 88 for North American Indians, and 86 for South American Indians. Since the sub-Arctic Indians living below the Eskimos scored almost as highly, perhaps there is a cline in intelligence down the continent, that may have reversed approaching the frigid area of Tierra Del Fuego, where brain sizes again inflated.

As to the second question, 'are race differences in intelligence genetic', this is not one question but a different one for each race. Again, since adoption studies are perhaps one of the best clues for this in the existing literature, hopefully I'll be able to provide some original insights to this shortly. Right now, the least convincing, I would say, are the low intelligence of other Eurasians, such as Middle Easterners, South Asians and Southeast Asians (this isn't to say not convincing). Most convincing, at this point (due to the most data) would be that sub-Saharan Africans score somewhat below Europeans, and that East Asians score somewhat above Europeans for reasons relating to genetics. Intermediate levels of evidence also suggests Australoids and Amerindians are somewhat less intelligent.

I put Southeast Asians in the 'least convincing' category for reasons discussed above, and Middle Easterners and South Asians (as well as Southeast Europeans) partly for some studies I have not mentioned here. But another important reason is that Lynn is chronocentric. The Middle East and India are relatively underdeveloped today, but have been ahead of Europe in the past; the Middle East relatively recently even. While it's possible that both these groups changed through time, this still seems to contradict Lynn who pushes the differences back deep in evolutionary time. According to Lynn, the Middle East and India never had high IQs (i.e. 100), because they were never exposed to the business end of ice age winters. But how to explain the times in semi-recent history when Islamic civilization, science and scholarship, was at a more advanced stage than Christian Europe? I suppose parallels exist even today, when a higher IQ Chinese population is temporarily more underdeveloped than the West, due to bad governance, etc. Still it's doubtful both that all intelligence differences are genetic, and that all the ones that are genetic have stood still for over ten thousand years. Lynn rightly points out that differences across space is a basic expectation from evolutionary theory, but differences across time are as well, and that all the major differences were formed when Lynn hypothesizes, requires us to believe that intelligence would stand still all that time after the evolutionary pressures of the last ice age, despite culture and environment creating many new selection pressures. Why should this be so, when Lynn demonstrates major genotypic selection in Dysgenics, just during the 20th century? I would put the major candidates for either change through time or "totally" environmentally depressed in central Eurasia, where history provides notable counterexamples and novel genes could flow as freely as the ancient trade routes.

Third, is there evidence that life in Northern Eurasia would require more intelligence? If we know the pattern exists and have better reasons to suspect genes than to suspect not, it is reasonable to reverse engineer the problem.

Consistent with the relatively higher intelligence we find with Eskimos, one of Lynn's best pieces of evidence that more intelligence is required in the northern latitudes than in tropical/subtropical ones are the tool kits manufactured by the hunter-gatherers in these respective latitudes. Hunter-gatherers in the latter group have on average about 10-20 tools, while the former have 25-60. These tools are also more complex, involving assembly of parts. This appears to be due to two main domains of challenge not faced in the tropical latitudes, warmth and hunting. Warmth of course, requires that iconic "caveman" challenge, of making and maintaining fire, more challenging in the cold snowy environment. It also requires making clothes for adults and infants and when necessary shelters. Where plant foods are available year round in the tropical/subtropics, diet consists almost entirely of gathering supplemented with minor hunting, while the opposite is true up north. Hunting required novel tools and techniques such as tracking and trapping large prey, as well as food storage.

Tools and tool complexity at least add a quantitative dimension to an otherwise verbal plausibility argument (of which Jared Diamond has provided more such evidence for his narrative). And as far as this goes we must ask why the cold is thought to raise intelligence, when it is the African environment, not the European one, that rapidly boosted and created human intelligence. Similarly, nowhere does Lynn mention a challenge in the Neanderthals who populated Europe. Neanderthals were not our ancestors, but our cousins. They were a non-human species (we know this through direct genetic evidence), but they had a recognizably human intelligence. They made skilled tools, and were excellent hunters. They made clothes, built fires and shelters, cared for their sick and buried their dead, and perhaps played music as well. They too migrated from Africa and became adapted to the European environment. While the Neanderthals may have been roughly equally intelligent, there is little reason to believe the frigid environment they were well adapted to had made them smarter than their African human counterparts, even though they could adequately do all the things Lynn argues Europeans later needed additional cognitive abilities to do. In fact the African humans moved up into the unfamiliar environment during conditions which had pushed down previous waves, and quickly displaced Neanderthals who had evolved in these conditions. The migrants had trade routes, which the Neanderthals did not, and their more sophisticated tools were copied by the retreating Neanderthals, not vice versa. So it would seem that the Africans immediately mastered these tasks, such as hunting, cloth and fire making, etc, that were supposed to increase their intelligence later, with intelligence they already had. And this intelligence evolved in the lower latitudes. Lynn's argument seems much smaller now since the important selective difference must not be between Africa and Europe, but between Europe and even colder Europe. Did making clothes and fire, storing food or trapping prey become even more complicated during the second ice age, because we know they already needed to and were able to do these things, with surprising superiority, before hand. Of course another genetic possibility is that these initial migrants were not a representative group, as they were able to move up into the Levant during an advancing ice age when previous groups of modern humans were unable to withstand these conditions. Richard Lewontin has argued that the high heritability of intelligence suggests that these between-individual differences, as relevant as they are to real-world outcomes today, haven't been much of a fitness characteristic in our evolutionary history and that they may have not been expressed the same or at all in ancestral environments. If this is true, genetic drift could be an even more likely explanation, if not a particularly romantic one.

As Steve Pinker recently pointed out in the 2006 Edge question he submitted, as an idea that's dangerous because it's probably true is that males and females and races differ in their abilities. And he has already cast his lot with Greg and Henry's Ashkenazi theory. Pinker highlights, as Charles Murray did in Commentary several months ago, that the tools now exist to test racial differences and they will probably be tested in this next ten years either directly or inadvertently. If even one well-done study finds a racial difference in cognitive ability, and this is likely, we can count on Lynn's work and others like it, including this book, getting an immediate flood of attention, as curiosities are piqued, taboos crumble and ambitious researchers fill the newly opened niche and quickly educate themselves on the topic with the best information available. And like it or not, on this score Lynn remains one of the only games in town. But it's a big topic for only a few scientists to take on by themselves and it is unlikely that they would get everything right as the first lonely ones to take a stab. So let's invite a lot more research on this topic, and the data will become cleaner, more sophisticated and more accurate. Something all of us should want.

Fig. 1

This chart summarizes the data available in RDiI. It is my approximate tally. The 'Majority' vertical column contains information on populations taken in countries where they form the basic majority. For example, Lynn lists 59 studies of East Asians taken in 5 different Asian countries such as Japan and Taiwan. The 'Minority' vertical column contains information on these same populations taken in countries where they form minorities. So Lynn lists 42 additional studies of East Asians done in 7 other (mostly Western) countries such as America and Britain. The third vertical series of columns are the combined values (they don't always add up perfectly because of coding issues. For instance admixture studies appear in the final tally but not the Majority/Minority columns because this complicates the issue). For Africa, 'Western' indicates the developed countries where blacks score about 85, and 'Non-Western' the developing countries (primarily in the Caribbean and Latin America) where they score about 70.

Barber, N. (2005). Educational and ecological correlates of IQ: A cross-national investigation. Intelligence 33, 273-284.

Berry, J. (1971). Psychological research in the north. Anthropologica 13, 143-157.

Clark, E. & Hanisee, J. (1982). Intellectual and adaptive performance of Asian children in adoptive American settings. Developmental Psychology, 18, 595-599.

Detterman, D. (1999). The psychology of mental retardation. International Review of Psychiatry. 11, 26-33.

Diamond, J. (2004). The wealth of nations. Nature, 429: 616-617.

Dickerson, R. (in press) Exponential correlation of IQ and the wealth of nations. Intelligence.

Hunt, E. & Wittmann, W. (in press) Relations Between National Intelligence and Indicators of National Prosperity. Fifth Annual Conference of International Society for Intelligence Research, New Orleans.

Jensen, A (1998). The g Factor. Westport,CT: Praeger.

Jones, G & Schneider, W (in press). Intelligence, human capital, and economic growth: An extreme-bounds analysis. Journal of Economic Growth, 11(1).

Jones, G. (2005). IQ in the Ramsey Model: A Naive Calibration. Working Paper, Southern Illinois University Edwardsville.

Lykken, D. (2004). The New Eugenics. Contemporary Psychology, 49, 670-672.

Lynn, R. ( 1983). "Reply to Stevenson and Azuma". Nature, 306, 292.

Lynn, R. (1990). The role of nutrition in secular increases of intelligence. Personality and Individual Differences, 11, 273-285.

Lynn R. (2002). Skin color and intelligence in African Americans: a reply to Hill. Population & Environment, 24, 215-218.

Lynn, R. (2004). The intelligence of American Jews. Personality and Individual Differences, 36, 201-207.

Mackintosh, N. (1998). IQ and Human Intelligence. Oxford: University Press.

Martin, N. (2001). Retrieving the 'eu' from eugenics. Nature, 414, 583.

McDaniel, Michael A. & Whetzel, D (in press). IQ and the Wealth of Nations: Prediction of National Wealth. Fifth Annual Conference of International Society for Intelligence Research, New Orleans.

Neisser, U. (2004). Serious scientists or disgusting racists? Contemporary Psychology, 49, 5-7.

Palariet, M (2004). Review of 'IQ & the Wealth of Nations'. Heredity, 92, 361-362.

Parra E, Marcini A, Akey J, Martinson J, Batzer M, Cooper R, Forrester T, Allison D, Deka R, Ferrell R, Shriver M (1998). Estimating African American admixture proportions by use of population-specific alleles. American Journal of Human Genetics, 63, 1839-1851.

Rosenberg N, Pritchard J, Weber J, Cann H, Kidd K, Zhivotovsky L, Feldman M (2002). Genetic structure of human populations. Science 298, 2381-2385.

Richardson, K (2004). Review of 'IQ & the Wealth of Nations'. Heredity, 92, 359-360.

Roth, P, Bevier, C, Bobko, P, Switzer, F, & Tyler, P. (2001). Ethnic group differences in cognitive ability in employment and educational settings: a meta-analysis. Personnel Psychology, 54, 297-330.

Rushton, J (1997). Cranial size and IQ in Asian Americans from birth to seven. Intelligence, 25, 7-20.

Stanton, W (1960). The Leopard's Spots. Chicago: University of Chicago Press.

Stevenson H, & Azuma H. ( 1983). "IQ in Japan and the United States". Nature, 306, 291-292.

Stevenson H, Stigler J, Lee S, Lucker G, Kitamura S., & Hsu C ( 1985). "Cognitive performance and academic achievement of Japanese, Chinese, and American children". Child Development, 56, 718-734.

Tang H, Quertermous T, Rodriguez B, Kardia SLR, Zhu X, Brown A, Pankow J, Province M, Hunt S, Boerwinkle E, Schork N, Risch N (2005) Genetic structure, self-identified race/ethnicity, and confounding in case-control association studies. American Journal of Human Genetics 76, 268-275.

Tanser, Harry A. (1939) The settlement of Negroes in Kent County, Ontario, and a study of the mental capacity of their descendants. Chatham, Ont.:Shepherd Publ., p 187.

Tanser, Harry A. (1941) Intelligence of Negroes of mixed blood in Canada. J. Negro Educ., 10, 650-652.

Templer, D. and Arikawa, H. (in press). Temperature, skin color, per capita income and IQ: an international perspective. Intelligence.

Voracek, M. (2004). National intelligence and suicide rate: an ecological study of 85 countries. Personality and Individual Differences 37, 543-553.


IQ and Health   posted by DavidB @ 2/01/2006 03:55:00 AM

A forthcoming article in the British Medical Journal provides evidence that IQ affects long-term health prospects, even after controlling for socio-economic factors, though these also have some independent effect. An abstract of the article is here. I think this research may already have been mentioned somewhere (I noticed it in today's London Times, but it seemed vaguely familiar), but it can do no harm to mention it again.

Added: I didn't mean to imply that this was the first research to show a link between IQ and health. As several people have pointed out, there are previous studies. But this one may be unusual in covering people fairly late in life (up to age about 70).


Sunday, January 29, 2006

Intelligence in UK declining?   posted by DavidB @ 1/29/2006 03:33:00 AM

Today's London Sunday Times (January 29) has an article in the Education section on new research which claims that British children's 'intelligence' has declined dramatically in the last 30 years. If the link works, the article is here.

The research is by Profs. Adey and Shayer of King's College London. Adey claims, based on a sample of 25,000 children, that 'the intelligence of 11-year-olds has fallen by three years' worth in the past two decades'.

Naturally this is of interest in the context of the Flynn Effect - the long term trend of rising IQ scores. Several recent reports suggest that the Flynn Effect has halted or gone into reverse.

I haven't been able to find any further details of the research than those in the ST article, and I suggest a need for caution. The tests used do not appear to be standard IQ tests but rather tests of 'scientific reasoning', which combine general intelligence (g) and more specific mathematical and physical concepts. In IQ terms, a fall of 3 years in average mental age at chronological age 11 would be massive: if we suppose the baseline 30 years ago is IQ = MA/CA = 11/11 x 100 = 100, the new IQ would be MA/CA = 8/11 x 100 = approx. 73. I don't think mean IQ can possibly have fallen by 27 points in 30 years! The school at King's College is also known for unorthodox views on the nature of intelligence, including the belief that 'thinking skills' can be radically improved by fairly small amounts of direct 'thinking' teaching.

I also note that there is no mention of the ethnic composition of the samples, which must certainly have changed in the last 30 years. However, in IQ terms the fall is far too large to be explained by compositional changes of this kind.

[Added: The last point should be sufficiently self-evident, but let me expand on it for the benefit of the innumerate. In 1975 the proportion of non-whites at age 11 in Britain was around 5%. In 2005 it was around 15%. (These are very rough figures, but good enough for the present purpose.) Let us suppose that in 1975 the mean 'intelligence' of white 11-year-olds, by standard IQ tests or any other valid instrument, was 100, while that of non-whites was 85. This is about the size of the black-white differential in the US, or the difference between whites and the offspring of recent non-white immigrants in European countries. It probably overstates the differential between whites and non-whites in Britain, since non-whites in Britain include large numbers of Indians and other high-achieving groups. Assume that white and non-white IQ is unchanged between 1975 and 2005. These assumptions gives us mean population IQ of 99.25 in 1975 and 97.75 in 2005 - a fall of less than 2 percentage points. This is far too small to account for the kind of decline reported by Adey and Shayer. To explain such a large decline by changes in the composition of the population, either the magnitude of the compositional change, or the differential between the different components, or both, must be much larger than is at all credible.]

Despite these reservations, this is clearly interesting research, and I will try to follow it up.

Added: I found a more informative account of the research in the Guardian here. The full report will be published in the British Journal of Educational Psychology next year.


Monday, December 19, 2005

Birth weight and IQ   posted by Theresa @ 12/19/2005 04:36:00 AM

Aftenposten, one of the leading newspapers in Norway, ran a story on Saturday about a study on birth weight and IQ conducted by Martha Gunn Eide, a researcher at the University of Bergen. (Eide is a medical doctor and this research represents her work toward a Doctorate of Medicine degree. Her thesis is entitled "Associations of Perinatal Conditions with Adult Body Size and Intelligence: A Register-based Cohort Study in Norway 1967-1999.")

Below the fold are some highlights from the article (apologies for the rough quality of my translation!) >>

"Store babyer faar hoeyest IQ" ["Big babies get highest IQ"]

The birth weight of a newborn baby boy has significance for intelligence, course [success] and income....

[Martha Gunn] Eide defends in a few days her Dr. Med. degree at the University of Bergen. She has completed a very comprehensive study based on the combined data of nearly 400,000 male children.

"Are there grounds to believe there is a correlation between birth weight and IQ also in girls?"

"There is no call to believe that this would be appreciably different for girls," says Eide, who is affiliated with The Department of Public Health and Primary Health Care, Faculty of Medicine at the University of Bergen.

Her study is based on information from the Medical Birth Register, Vernepliktsverket [compulsory military service department], the Statistics Central Bureau and the Rikstrygdeverket [Social Insurance department]. With this Eide has followed ca. 317,000 baby boys that were born in Norway between 1967-1979 through 18 years, as they met the [military] recruitment in period 1984-1999.

"The data are comprehensive facts analyzed for all boys in Norway over a 13 year period," says the Bergen researcher, who has worked four years on the project.

5200 gram

"What we find is that birth weight is important for IQ. Higher birth weight, higher IQ," says Kjell G. Salvanes [1], professor in Social Economics at the Norwegian School of Economics and Business Administration in Bergen....

Professor Salvanes has, together with two other international researchers, Sandra E. Black in Los Angeles and Paul J. Devereux in Dublin, investigated which factors are responsible for who takes higher degrees and get jobs with the highest pay....

godless discussed birth weight and IQ here while musing on C-sections as artificial selection.

[1] From the Cradle to the Labor Market? The Effect of Birth Weight on Adult Outcomes - Sandra E. Black, Paul J. Devereux, Kjell Salvanes


Friday, December 09, 2005

Jason on Seed on Pinker on Cochran on Jews   posted by Jason Malloy @ 12/09/2005 01:00:00 PM

Seed magazine has an article on Pinker's recent lecture at the Institute for Jewish Research, but the author recommends you listen to the podcast instead so you can hear her "authentic New York Jewish accent" which is vital to the piece, which doesn't discuss the theory so much as make fun of the audience (the article is sarcastically titled Jews on Jews: Jews are Great).

The author, (who is sympathetic enough to Pinker's presentation) is being light-hearted, but there is also a serious message:
And many [Jews] in attendance were there to hear that Jews are naturally smarter than everyone else.

So now they'll head out into the world, and spread the twisted word in their homes, at parties, in op-ed columns. And a paper that proposed an intriguing and plausible theory, and the man who eloquently analyzed it, will cause an impassioned backlash. Would that people were like genes and the deleterious ones weren't so darn dominant.

In reality though, a Jewish audience being open-minded for the "wrong" reasons and then heading to the media, is probably preferable (or at least more conducive to the scientific study of intelligence) than a Jewish audience being close-minded for the wrong reasons and heading to the media. Pinker and his audience are a welcome alternative to the vacuousness of much of Jennifer Senior's cover story for New York Metro a couple of months ago, where we were informed that, despite passing peer-review, Greg and Henry's paper is based on "exploit[ing] stereotypes" and does "not meet the standards of traditional scientific scholarship". The Metro article was chock full of helpful critiques such as "I'd actually call the study bullshit", along with de rigueur comparisons to cold fusion and Hitler (and Arthur Jensen's earlier attempts to "prove the racial inferiority" of blacks, etc.), and plenty of strategically cultivated misunderstandings (e.g. all Jews are smart).

Take as another example this op-ed last week in the Jerusalem Post. This author uses scare-quotes to describe the study as "scientific", and also suggests that most scientists think it's so much crankishness. Worse still the author goes on to tell us - "as an educator"; his professional opinion, of course - that we all have equal potential, and that "Psychologists maintain that the average person uses only 5-7% of that potential". It's doubtful from what I've read that any psychologists maintain this, and it sounds suspiciously like he's just parroting the sorry old wives' tale that "you only use 10% of your brain" (his number might come from pathological scientific fraud, Margaret Mead, who asserted we only use 6%).

In other words those who are being supportive, may or may not being doing so out of a self-serving feeling of "superiority", but at least they aren't slipping into absurd arguments or emotional bendings of the truth to do so, which is more than can be said for most people who have decided to take a "skeptical" [sic] stance.

Another problem for those that use bad arguments, is that they may not need to, and in fact may needlessly discredit their position with all of their tom-foolery. In fact a much bigger potential problem with the Ashkenazi theory isn't Jennifer Senior's "damning" condemnation of the paper's highly unscientific "lack of footnotes" [1], but may be with the psychometric data itself. As a new "In-Press" review of Richard Lynn's upcoming book Race Differences in Intelligence points out:
Another anomaly is that the IQ of Israel is only about 95, which although substantially higher than the median IQ of 85 found elsewhere in the region, is much lower than the IQ of Jews outside of Israel, estimated at between 108 and 115. Lynn breaks the Israeli IQ into three components: 40% Ashkenazim (European Jewish) with a mean IQ of 103; 40% Sephardim (Oriental Jewish) with a mean IQ of 91; and 20% Arab with a mean IQ of 86, which is virtually the same as that of Arabs elsewhere. Lynn suggests these differences could have arisen from selective migration (more intelligent Jews emigrated to Britain and the USA), intermarriage with different IQ populations (those in Europe versus those in North Africa), selective survival through persecution (European Jews were the most persecuted), and the inclusion of ethnic non Jews among the Ashkenazim in Israel as a result of the immigration of people from the former Soviet Bloc countries who posed as Jews.

103 is not appreciably different from the IQ of US whites (103 in the NLSY data, 102 in other datasets), and is noticeably lower than the area of Europe where Ashkenazi IQ was supposedly forged (e.g., the region of the Netherlands and Germany has IQs in the area of 106-107 [2]). Given that Lynn thinks this is an "anomaly" to be explained, he would seem to feel compelled by his data that Ashkenazi IQ in Israel is 103, rather than just manipulating a score he wants to see.

This would seem to pose a more significant problem for the Cochran-Harpending paper, than a lack of footnotes. I myself am skeptical of Lynn's numbers though, and await his book. Earlier reports of Ashkenazi IQ in Israel have been cited in Miles Storfer's Intelligence and Giftedness as 115 and higher, so it will be interesting to see Lynn's citations. And of course, there are other lines of evidence indicating a disproportionate amount of smart coming out of Israel.

Anyway, I'd rather skeptics exist but actually look skeptical in their criticisms, instead of, say, complaining about footnotes, misrepresenting the theory, or just using denial (e.g. asserting something was caused by genetic drift even after mathematical models point strongly against this).

[1] An ironic criticism, given that Charles Murray recently pointed out in How to Accuse the Other Guy of Lying with Statistics that many critics of The Bell Curve claimed that key bits of information were "buried" or "hidden" in footnotes - as if to deceive. Not sure how putting something in a footnote is "hiding" it, but just goes to show that you're damned if you do, damned if you don't with race and intelligence.

[2] According to Buj's European data at least. It is likely that these are biased upward with urban samples. Averaged across multiple studies and standardizations, these countries have IQs just like American whites - about 102-103.


Tuesday, November 29, 2005

Pinker on Ashkenazi IQ   posted by Razib @ 11/29/2005 07:16:00 PM

Steven Pinker is lecturing on Ashkenazi IQ in New York City in 2 days. If any GNXP reader who lives in New York wants to check it out and report back on what he says, the tickets are $11. Via Steve.


Thursday, November 03, 2005

A Cornucopia of New Intelligence Research   posted by Jason Malloy @ 11/03/2005 07:14:00 AM

Via my co-blogger and pro psychologist, Alex, I learn that the International Society for Intelligence Research is holding its 6th annual conference this December in Albuquerque, New Mexico, and by the looks of it, some very interesting research will be presented. Scientists exploring this important, difficult, controversial concept known as intelligence from many different disciplines and research paradigms - differential psychology, economics, sociology, neuroscience, evolutionary biology, paleoneurology, cognitive psychology, evolutionary psychology, artificial intelligence, genetics, animal cognition - are increasingly working together and combining their discoveries to powerful theoretical and empirical effect. For those interested, a PDF is available here with about 50 new abstracts for almost 60 presentations. Below the fold is a summary of the ones that I find the most interesting sorted by subject.

The Flynn Effect

Probably the most puzzling issue in psychometrics today is the Flynn Effect - the phenomenon of obsolete test norms as IQ scores continue to rise. The effect has caused problems or has had uncertain implications for any number of psychometric issues, including the authenticity of the rise itself, the black-white test score gap, the stability of intelligence with age, the effect of adoption studies, the actual IQ of the earlier generations of Asian Americans, and the existence of dysgenic trends.

Alexander Beaujean and Steven J. Osterlind follow recent reports of the Flynn Effect finally stopping, and even reversing, in Europe (see Alex's post here) in a presentation called Assessing the Lynn-Flynn Effect in the College Basic Academic Subjects Examination (Alex and David Burbridge have previously debated the nomenclature of the rise on GNXP here). Alex finds evidence, using special methods of test analysis based on Item response theory, that the Flynn Effect has started to reverse course in America as well.

And Jelte Wicherts, in Flynn Effect in the Woodcock-Johnson Cognitive Ability and Achievement Tests 1976-1999, uses Structural equation modeling techniques to explore whether Flynn gains have been an artificial score inflation (as Alex and I believe) or genuine gains in ability. Equally important, Wicherts attempts to explore whether the FE occurs between cohorts or to everybody at time of measurement (i.e. if you took an IQ test when you were 30, 40, and 50 would it be higher at each successive age (time of measurement), or would it remain stable for individuals across their lifespan, but three brothers age 6, 10, and 15 would be progressively stupider (cohort). Which one it is has meaningful implications for what's causing the rise (e.g. heterosis - a genetic cause - is only consistent with cohort). Previous evidence, such as the stability of IQ across 50+ year longitudinal studies, seem to falsify the TOM model.

On a related issue, Jan te Nijenhuis, et al. look into another area that might be plagued by "hollow" or fake IQ gains. IQ scores go up after retesting and through training programs. In Score Gains on g-Loaded Tests: No g the team demonstrate that these kinds of IQ boosts are not on the g factor (the business end of IQ), and suggest their results have implications for experiments that show schooling increases IQ. These increases may well be hollow.

Measurement and Mental Chronometry

One way to maybe better overcome this problem of "fake IQ gains" is getting at the underlying physical reality of intelligence. For instance, to determine if intelligence gains were "real" or not, we could measure the areas, tissues or structures of the brain that indicate intelligence or monitor more primal functions, such as things like how quickly or efficiently the brain registers simple stimuli through brain waves or glucose metabolism during problem solving. Issues of test bias and the potential of artifactual test gain would no longer be a problem because we could just clock the brain itself. Simple, more accurate, more efficient intelligence measurement is desirable and was Francis Galton's original vision for intelligence testing that ultimately lost out to Binet's measurement method.

One researcher who has helped revive Galton's model is Joseph Fagan, through his work with infants and young children. Habituation is a method for determining what’s going on in the heads' of infants less than one year old. By monitoring a baby's time spent discriminating stimuli, cognitive psychologists have determined innate or early notions of number and causality, evolutionary psychologists have determined culturally neutral standards of beauty and sex differences in social and object interests, and differential psychologists have tracked intelligence differences to the earliest months of life. In The Prediction, from Infancy, of Adult IQ and Achievement, Fagan et al. find that the correlation between the IQs of a sample of 20 year olds and their intelligence measured before the age of 1 is about .60. This is similar to earlier studies, which found the correlation between age 1 and age 11 was about .50.

Moving to the brain itself, a number of presentations come from Richard Haier and Rex Jung. Along with lead author Richard Colom in Correlated Vectors, g, and Gray Matter: A Frontal-Parietal Network and the Einstein Hypothesis they test the theory (named for the enhancement of this particular region in its namesake), through a number of lines of evidence, that the frontal-parietal network is key to individual differences in intelligence. They also review the current regions and structures of the brain known to be associated with intelligence.

Jung et al. also turn to the neurochemistry of intelligence in Biochemical Markers of Individual Differences in Cognitive Functioning, and "highlight the importance of white matter structural and chemical integrity to intellectual performance” which supports "the "neural efficiency" hypothesis that suggests optimal brain organization underlying individual differences in cognitive processes".

Finally, in Investigating the Cortical Temporal Dynamics of the Speed-Intelligence Relationship Using Magnetoencephalography (MEG), Robert Thoma uses MEGs to monitor the activity of the brain, to show that the regions involved in reaction time (RT) experiments (how quickly you lift your finger off a panel to turn off a light) are the same areas that show activity during complex intellectual tasks, suggesting RT is a simple and accurate measure of intelligence (something disputed by NJ Mackintosh in IQ and Human Intelligence, where it is argued that RT is a very nongeneralizable mental ability, not the same as g).

Group Differences

Those interested in HBD will not be disappointed, there are a number of presentations on race and sex differences, including a biggie from Greg Cochran and Henry Harpending titled The Evolutionary Biology of Human IQ Diversity: Some Current Directions and Hints. Fresh from their Ashkenazi notoriety, they discuss the far more contentious issue of Eurasian intelligence, with a new theory that fingers the Neanderthals!:
Modern humans apparently left Africa ca. 40,000 years ago and appeared soon afterwards in western Eurasia and in Australia. The southern arm peoples arrived with middle Paleolithic technology that persisted unchanged for tens of millenia while the northern arm peoples were host to the famous "creative explosion" of the upper Paleolithic with elaborate tools, worked bone, beadword and other adornment, sculpture, and painting. We discuss the hypothesis that incorporation of Neanderthal genes led to elevated intelligence (or something closely related) in the northern arm. We will mention some likely examples of such assimilated genes . . . We discuss the appearance and spread of an ASPM variant, one of the microcephalin complex genes, as an example. A puzzling pattern among candidate genes for elevating IQ is that they seem not to have spread in Africa

Additionally, two more talks add to and work off of Lynn and Vanhanen's Important book. In IQ & Wealth of Nations: Prediction of National Wealth, Deborah Whetzel and Michael McDaniel replicate Lynn and Vanhanen's findings and also find that education spending per student provides no incremental prediction of GDP beyond IQ. They examine a set of the highest predictors of GDP and find that economic freedom, health spending per capita and IQ explain 90% of the variance in national wealth (See also the Jones & Schneider paper and Garett Jones' newer paper (PDF)). Earl Hunt and Werner Wittmann also replicate Lynn and Vanhanen's finding in Relations Between National Intelligence and Indicators of National Prosperity, and add to it by examining cross-national student scholastic achievement from international datasets like PISA and TIMSS. They find a strong relationship between intellectual competence and economic indicators. In Criteria For Studies of Race and Intelligence, Earl Hunt also makes the case for agnosticism about genetics being the source of these (real and important) differences, with discussion of research ethics and study design for racial behavior genetics.

In Race Difference in General Intelligence g in Relation to Blood Pressure, Body Proportions, Hormones, and Personality, Helmuth Nyborg et al. test and reject another theory for the black-white IQ gap - that greater black hypertension plays a role in the difference.

Of course these kind of theories are DOA. The real problem is how to test the factor X theory, that the black-white IQ gap is due to something unique to the black environment that affects all blacks equally but is completely absent from the white environment in a way that could evade all detection thus far. A team of researchers published a paper (PDF) in 2003 responding to the well known argument that high within-group white and black heritability has no implications for their between-group IQ difference, showing that a common factor model "approach clarifies that absence of measurement bias implies common sources of within- and between-group variation" (earlier, the late David Rowe similarly showed, through an ingenious method of structural equation models using blacks and whites and their full and half siblings, that the source of the within group differences was also causing the between group difference). In Factorial Invariance and the Representation of Within-Groups and Between-Groups Differences: A Reconsideration Keith Widaman disputes their argument, but offers his own methods "for study design that will enable a test of the hypothesis that sources of within-group differences are also responsible for between-group differences".

On the sex difference front, Paul Irwing presents Sex Differences in General Cognitive Ability: A Reexamination of the Evidence, which seeks to question whether the 100 year old position in psychometrics - that there is no mean difference between men and women on IQ - is correct (as Jensen also concluded in 1998's The g Factor), or whether Richard Lynn's newer (1990>) position - that men have somewhat higher average IQs - is correct. Irwing concludes from large SPM samples that Lynn is correct (as was reported in the media a few months ago). Furthermore, he finds no evidence that this is due primarily to the male advantage in spatial visualization. Also, he finds that some research previously presented to show that there are no sex differences shows exactly the opposite.

David Puts et al. also present a meta-analysis titled Possible Organizational Effects of Early Androgens on Human Spatial Ability: Meta-Analyses of CAH and Digit Ratio Studies Showing that females that get a heavy dose of male hormones in utero also perform higher on spatial tasks like men do.


David Puts' finding has implications for the ridiculous Larry Summers' witch-hunt earlier this year as well. Rose Mary Webb et al. study the geniuses among us in Spatial Ability: A Neglected Dimension in Talent Searches for Intellectually Precocious Youth, and find using longitudinal data that children with high spatial abilities (who - a la Puts - are going to be disproportionately male) have higher levels of interest in math and science ("theoretical" endeavors) and that the ability can be used to predict which gifted students follow scientific or humanities pathways. Similarly, Summers' critics have tried to rebuff the annoying fact that many more men score at the top of the ability distribution by asserting that IQ/test score ability stops being meaningful at the higher levels of ability anyway (that is, conveniently, at the precise point where the male/female ratio starts to get ridiculously incongruous. e.g. 7 to 1 in the top 1%). In Creative Accomplishments Covary With Ability Even Among the Top 1%, Jonathan Wai et al. show this is nonsense; IQ keeps discriminating between levels of creative and career achievement (such as earning a math-science PhD, securing a patent, and achieving tenure at a top 50 U.S. university), even at the very skinny right tail of the ability distribution. (and it keeps on going: IQ even distinguishes those in the top .0001%!)

Two additional presentations on those at the right tail, An Examination of Spearman's Law of Diminishing Returns by Christopher Condon and David Schroeder and A Test of Spearman's Law of Diminishing Returns in the Kaufman Assessment Battery for Children, Second Edition by Matthew Reynolds and Timothy Keith, test Spearmen's idea that the g factor is more important at low IQ levels, and that lower order factors are more independent and important at progressively higher ability levels. Using different data sets both studies find support for this. "Multiple intelligences" (and not the fictional Gardner ones) are only something for the very smart, for people at the left tail it's all about g.

The Evolution of Human Intelligence

A number of presentations attempt to tie general intelligence into the framework of human evolution. James Lee's The Evolution of General Intelligence in the Primate Clade, for instance, talks about research showing that mental testing across primate genre best distinguishes them by a single general factor (see also the latest issue of Behavior Genetics for a detailed exploration of the g factor in mice). The correlation between brain size and the g factor across 25 primate genre is .77. Lee discusses this in the context of Bruce Lahn's recent papers.

David C. Geary uses material from his fascinating new book in The Origin of Mind: Evolution of Brain, Cognition, and General Intelligence. Geary argues that "The primary dynamic that has driven and is currently driving human evolution is competition with other people and groups of other people for resource control" and that intelligence involves the ability to form more accurate "mental models" of the outside world, and that the systems to build these models "are known as general fluid intelligence, working memory, and attentional control" and that "The combination of these systems and folk knowledge is the foundation upon which human intellectual and cultural advances have been built".

In contrast to Geary, Linda Gottfredson argues in Innovation, Fatal Accidents, and the Evolution of General Intelligence that competition with other people hasn't been the primary engine of human intellectual evolution, but instead that each boost in intelligence led to new technologies which created new dangers that continuously pruned off those at the bottom of the spectrum. Innovation then would boost IQs through increased selection, which would thus lead to even more innovation, and the cycle fuels itself. (her paper, by the way, is one of the few that can already be found online. Here (PDF).

Kim Hill presents The Adaptive Function of High Cognitive Ability in Hunter-Gatherers: Feeding Niche or Social Complexity?, where an IQ study of modern hunter-gatherers is discussed. In support of David Geary and the modern consensus of "Machiavellian intelligence", it was found that higher IQs in this group were associated with higher social status. Contradicting the old "Man the Hunter" theory of intelligence, Hill reports that there was no association between hunting prowess and measured intelligence.

In Mutual Mate Choice for Intelligence as a Fitness Indicator, Geoffrey Miller uses research from evolutionary psychology to support his theory that sexual selection was responsible for driving up human intelligence. And in a related lecture, Intelligence and Mate Choice, Mark Prokosch explores the assumptions behind the sexual selection theory (e.g. how important is intelligence in long and short term mates? How accurately do females judge intelligence?) and tests some of them directly.


A number of other presentations deal with the issue of "Emotional Intelligence" (empty) and "Life History Theory" (all the presented papers fail to support it). I do not find those issues interesting, but the abstracts are in there for you. A few more deal with technical issues, such as test refinement, which are no doubt important to the field but less fun to talk about. The last one I'll leave you with, though, might be of interest if you've ever had the misfortune to encounter Internet ads, and says all it needs to just in the title: Web-Based IQ Tests: A Concept Whose Time Has Not Yet Come.