Wednesday, September 23, 2009

American "Nones", sex differences   posted by Razib @ 9/23/2009 11:49:00 AM

American Religious Identification Survey 2008 has a new survey, American Nones: The Profile of the No Religion Population. Not surprising, but interesting:
There are a couple of additional findings worth noting here. Looking at retention by gender, Nones are more likely to retain men than women: 66% of men who reported no religion at age 12 were Nones at the time of their participation in ARIS 2008, but only 47% of females who reported no religion at age 12 remained Nones. Of those who reported having a religion at age 12, 15% of men left while only 9% of women did. It appears that American women have a greater affinity for religion than men. And conversely men have greater affinity for secularity than women.

Also, 49% of male "Nones" are atheists & agnostics in terms of stated beliefs. 36% of female "Nones" are. In terms of asserting that one is an atheist or agnostic, 11% of male "Nones" admit to that, while 8% of females do.

Related: Male vs. female religiosity difference.

H/T Talk Islam

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Wednesday, May 27, 2009

Sex differences and variation in personality   posted by Razib @ 5/27/2009 05:21:00 PM

Look before you leap: Are women pre-disposed to be more risk averse than male adventurers?:
"It's not at all that women are risk averse," says Jody Radtke, program director for the Women's Wilderness Institute in Boulder, Colorado. When men are confronted with challenging situations, they typically produce adrenaline, which is what causes them to run around, hollering like frat boys at a kegger. An adrenaline rush is a good feeling, but when confronted with the same situation, women produce a different chemical, called acetylcholine.

"Pretty much what (acetylcholine) does is it makes you want to vomit," says Jody.

Because women don't have the same positive chemical reward, they tend to be less pumped about confronting stressful situations. This leads them to rely on decision-making. Essentially, they want the whole picture before they go diving in.

Research, Jody says, shows women have more cross-networking between the two hemispheres of the brain, which subconsciously allows them to evaluate different sensory cues, facts and emotions when making decisions. The cause of this difference probably lies somewhere in the debate of nature versus nurture and the history of evolution.

Marvin Zuckerman, professor emeritus at the University of Delaware, has studied risk for decades. He found men are typically more likely to take risks when seeking novel or exciting sensations, and that comes from both genetics and environment.

"What's important seems to be the environment that isn't shared by siblings in the same family," he says.

The above was originally published by Women's Adventure Magazine. The last reference is to the repeated finding that non-shared environment matters a great deal but isn't well accounted for. Obviously both men and women vary in terms of psychological attributes, and there have been plenty of attempts to adduce the variation to different quantities of neurochemicals (the "chemical soup" model is easy to translate into prose).

The content of the piece isn't too surprising, you see it all the time. Suggesting innate differences between men and women is totally acceptable so long as it is perceived to be neutral, or, better yet, casts women in a positive light. Michael Lewis' recent article on the Icelandic financial turmoil hints to sex differences and male psychology as a root problem. He presented a rather conventional stereotype of men as financial cowboys willing to take outsized risks for reward, while women were risk averse socialists. During the run up to the Iraq War and afterward I recall many people, mostly but not always women, calling into Leftish radio shows promoting a sex determinist theory that war was the result of the male nature, and the fact that men are head of states of most nations was the ultimate problem (this argument crops up in science fiction as well).

The interesting point to me is the sort of articles which highlight "different ways of thinking" between the sexes and how they might be rooted in biological differences have implications which point in different directions in terms of positive or negative valuation depending on your perspective and circumstance. As a specific example, the risk taking predispositions of many males can be seen to be folly and lack of prudence, but, risk often entails both an upside and a downside. Decisions which may seem foolish and wrongheaded viewed through a conventional mainstream lens are often lauded in hindsight as visionary. Unfortunately the nature of uncertainty is such that one has little idea which risks will pay off and which will simply extract a downside cost. It is likely that human societies dominated by those who are only risk averse, or those who are only risk accepting, would not be those which we would truly wish to live in. Variation in human personalities is probably beneficial in an aggregate sense when it comes to human progress. There are downsides risks to both the risk averse and risk accepting strategy, so it is probably best to have some of both. In an economic scenario what I'm talking about is straightforward; consider two individuals with degrees in computer science, one who goes to work for IBM and another who founds a start-up. You wouldn't want everyone to aspire to become a corporate employee, where would the innovation which drives productivity growth come from? On the other hand, there are only so many start-ups which succeed and there is a need for individuals who work in less sexy sectors who service older established technologies which are at the heart of the current economy. In other words, you want to be able to squeeze more juice from the oranges you have, as well be funding research which might result in the discovery of jucier varietals.

Addendum: Obviously what I'm saying here isn't too novel. It's rooted in human nature itself: our minds are cobbled together from disparate competencies and subfunctions, and our unitary consciousness is a delusion very successfully promoted by the prefrontal cortex. But even when it comes to concepts and assumptions which are the purview of the prefontal cortex its priority isn't usually to keep its story straight. Rather it seem geared toward generative ad hoc narratives which are only proximately consistent. Yes it can engage in rationality, but most of the time its forte is rationalization. And why not? Rationalizing the contradictory feels good! It was almost certainly highly adaptive in the past, and likely is today, in terms of keeping everyone in the group on the same page.

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Monday, April 06, 2009

Estrogen & economics   posted by Razib @ 4/06/2009 11:03:00 PM

A randomized trial of the effect of estrogen and testosterone on economic behavior:
Existing correlative evidence suggests that sex hormones may affect economic behavior such as risk taking and reciprocal fairness. To test this hypothesis we conducted a double-blind randomized study. Two-hundred healthy postmenopausal women aged 50–65 years were randomly allocated to 4 weeks of treatment with estrogen, testosterone, or placebo. At the end of the treatment period, the subjects participated in a series of economic experiments that measure altruism, reciprocal fairness, trust, trustworthiness, and risk attitudes. There was no significant effect of estrogen or testosterone on any of the studied behaviors.

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Tuesday, February 24, 2009

Male superiority at chess and science cannot be explained by statistical sampling arguments   posted by agnostic @ 2/24/2009 05:37:00 PM

A new paper by Bilalic et al. (2009) (read the PDF here), tries to account for male superiority in chess by appealing to a statistical sampling argument: men make up a much larger fraction of chess players, and that the n highest extreme values -- say, the top ranked 100 players -- are expected to be greater in a large sample than in a small one. In fact, this explanation is only a rephrasing of the question -- why are men so much more likely to dedicate themselves to chess.

Moreover, data from other domains where men and women are equally represented in the sample, or where it's women who are overrepresented in the sample, do not support the hypothesis -- men continue to dominate, even when vastly underrepresented, in domains that rely on skills that males excel in compared to females. I show this with the example of fashion designers, where males are hardly present in the sample overall but thrive at the elite level.

First, the authors review the data that male chess players really are better than female ones (p.2):

For example: not a single woman has been world champion; only 1 per cent of Grandmasters, the best players in the world, are female; and there is only one woman among the best 100 players in the world.

The authors then estimate the male superiority at rank n, from 1 to 100, using the entire sample's mean and s.d., and the fraction of the sample that is male and female. Here is how the real data compare to this expectation (p.2):

Averaged over the 100 top players, the expected male superiority is 341 Elo points and the real one is 353 points. Therefore 96 per cent of the observed difference between male and female players can be attributed to a simple statistical fact -- the extreme values from a large sample are likely to be bigger than those from a small one.

Therefore (p. 3):

Once participation rates of men and women are controlled for, there is little left for biological, environmental, cultural or other factors to explain. This simple statistical fact is often overlooked by both laypeople and experts.

Of course, this sampling argument doesn't explain anything -- it merely pushes the question back a level. Why are men 16 times more likely than women to compete in chess leagues? We are back to square one: maybe men are better at whatever skills chess tests, maybe men are more ambitious and competitive even when they're equally skilled as women, maybe men are pressured by society to go into chess and women away from it. Thus, the question staring us in the face has not been resolved at all, but merely written in a different color ink.

The authors are no fools and go on to mention what I just said. They then review some of the arguments for and against the various explanations. But this means that their study does not test any of the hypotheses at all -- aside from rephrasing the problem, the only portion of their article that speaks to which answer may be correct is a two-paragraph literature review. For example, maybe females on average perform poorer on chess-related skills, and so weed themselves out more early on, in the same way that males under 6'3 would be more likely to move on and find more suitable hobbies than basketball, compared to males above 6'3. Here is the authors' response to this hypothesis (p. 3, my emphasis):

Whatever the final resolution of these debates [on "gender differences in cognitive abilities"], there is little empirical evidence to support the hypothesis of differential drop-out rates between male and females. A recent study of 647 young chess players, matched for initial skill, age and initial activity found that drop-out rates for boys and girls were similar (Chabris & Glickman 2006).

Well no shit -- they removed the effect of initial skill, and thus how well suited you are to the hobby with no preparation, and so presumably due to genetic or other biological factors. And they also removed the effect of initial activity, and thus how enthusiastic you are about the hobby. And when you control for initial height, muscle mass, and desire to compete, men under 6'3 are no more or less likely to drop out of basketball hobbies than men over 6'3. How stupid do these researchers think we are?

So, this article really has little to say about the question of why men excel in chess or science, and it's baffling that it got published in the Proceedings of the Royal Society. The natural inference is that it was not chosen based on how well it could test various hypotheses -- whether pro or contra the Larry Summers ideas -- but in the hope that it would convince academics that there is really nothing to see here, so just move along and get home because your parents are probably worried sick about you.

Now, let's pretend to do some real science here. The authors' hypothesis is that the pattern in chess or science can be accounted for by their statistical sampling argument -- but of course, men dominate all sorts of fields, including where they're about as equally represented in the pool of competitors, and even when they're outnumbered in that pool. Occam's Razor requires us to find a simple account of all these patterns, not postulating a separate one for each case. The simple explanation is that men excel in these fields due to underlying differences in genes, hormones, social pressures, or whatever.

The statistical sampling argument can only capture one piece of the pattern -- male superiority where males make up more of the sample. Any of the non-sampling hypotheses, including the silly socio-cultural ones, at least are in the running for accounting for the big picture of male dominance regardless of their fraction of the sample.

To provide some data, I direct you to an analysis I did three years ago of male vs. female fashion designers. Here, I'll consider "the sample of fashion designers" to be students at fashion schools since that's what the data were. Fashion students are the ones who will make up the pool of fashion designers upon graduating. I included four measures of eminence: 1) being chosen to enter the Council of Fashion Designers of America, 2) having an entry in two major fashion encyclopedias, both edited by women (Who's Who in Fashion, and The Encyclopedia of Clothing and Fashion), 3) having their collections listed on Vogue's website, and 4) winning the highest award of the CFDA, the Perry Ellis awards for emerging talent.

The male : female ratio in the pool of fashion students is 1 : 13 at Parsons and 1 : 5.7 at FIT. So, the female majority in the sample of fashion designers is not quite as extreme as that of males in chess leagues, but pretty close. The statistical sampling argument predicts that females should out-number males at the top. But they don't -- the M : F ratios for the four measures above are, respectively, 1.29 : 1, 1.5 : 1 and 1.9 : 1, 1.8 : 1, and 3.6 : 1. Again, this isn't as extreme as male superiority in chess, but recall that males are so underrepresented in the sample to begin with!

(For other design fields that males tend to have greater interest in, such as architecture, the M : F ratios among the winners of the Pritzker Prize and the AIA Gold Medal are, respectively, 27 : 1 and 61 : 0).

The authors statistical sampling argument is not a null hypothesis that we reject or fail to reject in any particular case -- rejecting it in fashion design, and failing to reject in chess. It is not a hypothesis at all, but simply a rephrasing of the observation that men dominate certain fields, only measuring this by their greater participation rates. Again, it does not address why males are so much more likely to participate in chess leagues to begin with, which could be due to any of the existing hypotheses about male superiority. The point is that it is a widespread phenomenon that requires a single explanation applying across domains.

I find the genetic and hormonal influences on the mean and variance of cognitive ability and personality traits to be the most promising (just search our archives for relevant keywords to find the discussions). But this study of chess players offers nothing new to the debate, and could not do so even in principle, as it doesn't make a novel hypothesis, apply a novel test to existing data, or apply existing tests on novel data. You can reformulate the observation or problem however you please, but that doesn't make the testing of hypotheses go away.


Bilalic, Smallbone, McLeod, and Gobet (2009). Why are (the best) Women so Good at Chess? Participation Rates and Gender Differences in Intellectual Domains. Proc. R. Soc. B, 276, 1161–1165.

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Wednesday, January 21, 2009

Women overeating, an impulse control issue?   posted by Razib @ 1/21/2009 10:28:00 PM

Evidence of gender differences in the ability to inhibit brain activation elicited by food stimulation:
Although impaired inhibitory control is linked to a broad spectrum of health problems, including obesity, the brain mechanism(s) underlying voluntary control of hunger are not well understood. We assessed the brain circuits involved in voluntary inhibition of hunger during food stimulation in 23 fasted men and women using PET and 2-deoxy-2[18F]fluoro-D-glucose (18FDG). In men, but not in women, food stimulation with inhibition significantly decreased activation in amygdala, hippocampus, insula, orbitofrontal cortex, and striatum, which are regions involved in emotional regulation, conditioning, and motivation. The suppressed activation of the orbitofrontal cortex with inhibition in men was associated with decreases in self-reports of hunger, which corroborates the involvement of this region in processing the conscious awareness of the drive to eat. This finding suggests a mechanism by which cognitive inhibition decreases the desire for food and implicates lower ability to suppress hunger in women as a contributing factor to gender differences in obesity.

ScienceDaily has a lot more:
"The finding of a lack of response to inhibition in women is consistent with behavioral studies showing that women have a higher tendency than men to overeat when presented with palatable food or under emotional distress," Wang said. "This decreased inhibitory control in women could be a major factor contributing to the observed differences in the prevalence rates of obesity and eating disorders such as binge eating between the genders, and may also underlie women's lower success in losing weight while dieting when compared with men."

Here's a question: do the sexes differ in time preference?


Monday, July 28, 2008

The MSM on the new math/gender study.   posted by Herrick @ 7/28/2008 08:26:00 PM

Tabarrok nails it.

Agnostic adds: Here's a graph using the new study's finding of same mean for males and females, and taking male to female ratio in variances to be 1.16 (they estimate it between 1.11 and 1.21). This is the ratio of a normal with mean = 0 and s.d. = 1.077 (male) to a standard normal (female). It's shown for above-average people, but it's symmetric about 0: males have more geniuses and more idiots. The dashed green line is M:F = 1, or perfect gender parity. Males are underrepresented between -1 and +1 s.d., and overrepresented outside this interval. You may have to click on the image to see it full-size.


Friday, July 18, 2008

sextroverts   posted by ben g @ 7/18/2008 01:20:00 PM

Truism of the day: Introverted nerds don't get laid much. Or, in more scientific terms, extroversion in men is linked to a higher number of sex partners.[1] Men and women have similar levels of extroversion, though-- in fact, women have slightly higher levels of it.[2] This begs for explanation; after all, extroversion is significantly heritable (~50%)[3], so why shouldn't it have been positively selected for in males?

It turns out that, while men aren't more extroverted than women, they are more extroverted in the areas where it "counts.""The table below[2] of extroversion and its sub-traits sheds some light:

TraitMean Difference (Female - Male)High (%F)Very Low (%F)
Sensation seeking-1.54270
Positive emotions1.37836

(mean difference is the mean difference between men and women on the trait. high %F and low %F are the percent of women who are at the very high and very low tail-ends of the distribution.)

With the exception of 'ideas' (F-M=-1.6), a sub-trait of Openness to Experience, none of the 30 Big-Five sub-traits show more skew towards men than do assertiveness and excitement-seeking. While these -.9 and -1.5 mean differences may seem minor on their face, it is worth considering how they affect the tails of the distributions. In the case of sensation-seeking, 70% of people who are significantly low on excitement-seeking are female. A great deal of meaningful sexual dimorphism here, so let's look into it...


Browsing through the sensation-seeking literature I came across this very interesting study; sensation-seeking was one of many variables examined in a study of college mens' number of sexual partners.[4] The other variables looked at (and all measured through questionnaires unless otherwise indicated) were: age, attractiveness (measured by self-rating, and female, male interviewer ratings), social intimacy, sexual affect, dominance, hypermasculinity, Eysenck's psychoticism trait measure, and testosterone levels (measured chemically through saliva samples).

Sensation seeking correlated more so than any other variable with both lifetime number of sexual partners (.38) and with maximum partners in one month (.37). Trailing way behind it was hypermasculinity (.29, .29), followed by attractiveness (.20, .28).[4,5]

I'm not going to attempt to unwind the complex causal chains which correlate sensation-seeking to short term mating success. It should suffice to say that there is significant evidence that these traits are both intrinsically attractive to women, and that they serve as an impetus to sexual pursuit of women by men in the first place.[7] Sensation- seeking has the highest narrow-sense heritability of any (Big-5) sub-trait-- .36, and a relatively high broad-sense heritability of .52, by the way.[3]

A Pet Hypothesis

It seems plausible that sensation-seeking garnered a greater number of female mates in the Pleistocene , just as it does now, and that there was therefore positive selection for it in men. I would posit that if this positive selection existed, it was limited in effect by the negative aspects of extroversion, visible in our day in age-- extroverts are more at risk for STD's, being jailed, getting in fights, and generally doing stupid risky things.

The fact that Extraversion has a higher degree of heritability in men than in women (.57 versus .38)[3] might be considered as evidence. I am not knowledgeable enough of the behavior genetics involved to say whether this is meaningful evidence.

The most specific, and testable part of my hypothesis is this: that ADHD (note that I'm not saying ADD) is to some extent the result of "overclocking" for male sensation-seeking. Consider this-- estimates of the male:female ratio for ADHD range from 4:1 to 9:1.[8] People with ADHD are more extroverted than other people, yes, but they are especially more sensation-seeking than other people. Unsurprisingly, people with ADHD have a higher number of sexual partners than people without.[9] The discrepancy between males without ADHD and those with it is probably underestimated because of the widespread use of drugs like Ritalin.


1. (Nettle 2004).
2. (Corbitt & Widiger 1995). See the table in their article for all of mean differences and percentile differences at the tails of the bell curves between men and women.
3. (Loehlin & Bouchard, 2001)
4. (Bogaert et. al 1995)
5. Sensation seeking correlated trivially with age, .14 with Attractiveness, .26 with dominance, .41 with hypermasculinity, and .45 with psychoticism. Statistically eliminating virgins from the sample had no major effects on these correlations. For you data crunchers out there I suggest you read the study yourself if you want to analyze their factor and regression analyses.
6. (McCoul & Haslam 2001).
7. There's a good summary of some of the studies on why sensation-seeking might cause more mates in (McCoul & Haslam 2001).
8. (Gutman 2002)
9. (White 1998)

  • Nettle, D. (2004). An evolutionary approach to the extraversion continuum. Evolution and Human Behavior
  • Corbitt, E.M. and W.A. (1995). Sex Differences Among the Personality Disorders: An Exploration of the Data. Clinical Psychology: Science and Practice.
  • Loehlin, J.C., & Bouchard, T.J. (2001). Genes, Evolution, and Personality. Behavior Genetics.
  • Bogaert, A.F. and Fisher, W.A. (1995). Predictors of University Men's Number of Sexual Partners. The Journal of Sex Research
  • Maryann D. McCoul and Nick Haslam (2001). Predicting high risk sexual behaviour in heterosexual and homosexual men: the roles of impulsivity and sensation seeking. Personality and Individual Differences
  • Gutman, A. (2002). ADHD -- Perspectives From Child to Adult. Retrieved July 18, 2008, from the MedScape Web site
  • White, J.D. (1998). Personality, temperament and ADHD: a review of the literature. Personality and Individual Differences.
  • Kate et al (2006). Childhood ADHD Predicts Risky Sexual Behavior in Young Adulthood. Journal of Clinical Child and Adolescent Psychology

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Tuesday, July 08, 2008

Summers part 29,476   posted by Herrick @ 7/08/2008 09:43:00 PM

Slate has been having a debate on sex differences. Along the way, they hit on a key Summers issue: The apparent higher male variability of math scores. Shaffer, the author, refers to the classic Feingold piece, a cross-cultural meta-study of the variability of mental abilities across genders. Shaffer makes the common claim that there are data on both sides--sometimes women have a higher variance, and sometimes the men do. But is the difference statistically significant?

I did a simple analysis of Feingold's data from 54 math tests from 20 countries, and 19 tests of spatial ability from 9 countries. I ran least squares and least absolute deviation tests.

Here are the p-values for the restriction that men and women have equal variability:

Math, least squares: p<0.1%
Math, least absolute deviation: p<5%
Spatial, least squares: p<10%
Spatial, least absolute deviation: p=11% (but only 19 observations!)

OK, so it's reasonable to conclude that men have higher variability in this cross country sample, and that the cases of greater female variability are just flukes. But are the differences quantitatively significant, not just statistically significant?

Feingold, the author of the study, says no. He notes: "The median V[ariance]R[atio] of 1.09 indicated greater male variability [on math tests]," then claims that "the magnitude of the gender difference was trivial." Not so. Excel will show you that three or four standard deviations above the mean--Larry Summers territory to be sure--that's enough to get you a 2-to-1 one ratio. And that's with no difference in means whatsoever.

This paper (Table 1, page 10) works out the rough gender ratios you'd expect to see under various assumptions for means and variances. The bottom line is no surprise: with small differences in means plus small differences in variance, you can get big results: 4 to 1 ratios are easy to come by, and 10 to 1 are plausible. Yes, yes, further research is needed, but most of the research is pointing in the same direction. And we Bayesians know what to do when research mostly points in one direction....

(Oh, and the median male/female variance ratio for spatial ability in Feingold's data is 1.14. And yes, none of this gets at genes v. culture. But let's start with the journalism before we head to causation.)

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Monday, May 19, 2008

What are men good for?   posted by agnostic @ 5/19/2008 12:33:00 AM

I came across an interesting 2007 talk that social psychologist Roy Baumeister gave to the American Psychological Association, "Is There Anything Good About Men?" He informally reviews the literature on sex differences in ability and motivation. Some of it will be old news for readers, such as the discussion of Larry Summers, but there's quite a lot that will not. Some interesting tidbits:

- Most people in the West now believe that women possess more desirable qualities than men do. (Agreed -- I only interact with males as colleagues, keeping all of my friends female.)

- Women are more likely than men to commit violence against an intimate partner.

- About 80% of those who work 50-hour weeks are men.

- 93% of those killed on the job in the US are men.

- Men appear more oriented toward large-scale social groups where relationships are shallow but many, women toward small-scale groups where they are deep but few. Baumeister suggests that this is a key source of male-female inequality after the transition to agriculture: men were more suited to the large-scale networks that came to run social, political, and economic life.

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Sunday, May 11, 2008

Gender differences in the brain?   posted by Razib @ 5/11/2008 11:17:00 PM

Gender Differences in the Mu Rhythm of the Human Mirror-Neuron System:
The present findings indirectly lend support to the extreme male brain theory put forward by Baron-Cohen (2005), and may cast some light on the mirror-neuron dysfunction in autism spectrum disorders. The mu rhythm in the human mirror-neuron system can be a potential biomarker of empathic mimicry.

Don't know enough about this stuff to comment, but figure readers would find it of interest....


Tuesday, January 22, 2008

Gender bias in publications?   posted by Razib @ 1/22/2008 10:52:00 PM

Check out this post. I found it via Research Blogging. I'm going to try out the RSS when they get it up and see if it's worth it....


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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Friday, May 12, 2006

Sexual dimorphism in skin color   posted by Razib @ 5/12/2006 03:05:00 PM

Dienekes points me to this piece in The American Journal of Physical Anthropology which concludes that there isn't greater sexual dimorphism in skin color in areas where social/sexual selection could presumably operate because of relaxation of natural selection. Remember that sexual dimorphism tends to evolve very slowly (you need to have sex-linked or developmentally modified loci since men and women share almost all the same genes [except for the Y]), perhaps an order of magnitude more slowly than standard phenotypic evolution given the same selection pressure.

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Saturday, January 28, 2006

Peter Frost, dark men & fair women   posted by Razib @ 1/28/2006 10:55:00 AM

Since very few of you have likely read Fair Women, Dark Men: the Forgotten Roots of Racial Prejudice by Peter Frost, I'd like to you point you to his website, where he introduces many of his ideas in a series of essays. Steve also has an essay on based on Frost's ideas, and you might find this paper by Frost, European hair and eye color A case of frequency-dependent sexual selection?, of interest.

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