Tuesday, June 23, 2009

Class and opposition to teenage sex: A life history perspective   posted by agnostic @ 6/23/2009 02:51:00 AM

The GSS asks people about the morality of premarital sex between post-pubescent minors (TEENSEX):

What if [a male and female] are in their early teens, say 14 to 16 years old? In that case, do you think sex relations before marriage are always wrong, almost always wrong, wrong only sometimes, or not wrong at all?

Most people say "always wrong," so I'll just look at those responses; the other responses have little room to vary since all must add up to 100%. How does opposition vary across demographic groups? [1] As for social class, the elites say they're more ethical than the rabble, but on the other hand, they're big supporters of "sex is natural and therefore can't be harmful." So which is it?

Let's see what the data say:

Clearly, those with more prestigious jobs (SEI) are less opposed. Perhaps this is because the prestigious can get away with more shocking or outside-the-mainstream views. But that's not what the three other measures of social class suggest.

As for real income (REALINC, in $5000 intervals), opposition increases from poor to lower-middle income people ($40K), and then declines somewhat steadily among middle and upper income people. My guess here is that middle and upper income people don't think the teenage years count -- as long as their kids get advanced degrees, make a lot of money, and don't marry scumbags, they could care less if they fool around a little in high school.

Poor people, though, see their kids as living shorter lives -- they enter Adult World sooner, so it matters what they do right after puberty. If you live in the same town you grew up in and plan to get married in your early 20s, having a reputation as a slut in high school will harm your prospects a lot more than if you move across the country five times before marrying, and even then only 10 years after graduating.

Education (EDUC) and intelligence (WORDSUM) show a similar pattern to job prestige and real income, as all are indicators of social class. Opposition increases up through 6th grade graduates, but declines pretty steadily among those who made it through middle school and beyond. For intelligence, like the other class variables, there's an increase among the below-average, and then a steady decline among the above-average.

So, judging by these four ways of measuring social class, there seems to be a real difference between the upper, middle, and lower groups in how fast or slow they expect their children to grow up and do adult things. In biology jargon, this is a difference in life history strategies. There's a parallel here between parents who invest more in their sons or their daughters, according to the Trivers-Willard Hypothesis: richer families favor their sons, while poorer families favor their daughters. One study found support for this idea by looking at how Gypsy vs. Hungarian families in Hungary invested in their children (free PDF here). Since lower class families care more about their daughters, they'll freak out more if they engaged in premarital sex while still young and thus when reputations matter most. Upper class families will be thinking of their sons, though, and conclude, "Meh, let them sow their wild oats, as long as they settle down when the time comes."

[1] It seems like younger people would be least opposed, since 14 to 16 is awfully close to their own age. They might think the police will come after them next. Sure enough, age is a very strong predictor here -- indeed, the only demographic group I could find among whom a majority doesn't consider it "always wrong" is 18 year-olds.

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Thursday, January 08, 2009

Teen birth rates up, but nothing to worry about   posted by agnostic @ 1/08/2009 07:48:00 PM


After declining pretty steadily from 1991 to 2005, in 2006 teen birth rates showed a slight uptick. Rather than swallow what the mass media and doomsaying blogosphere infers, read the report for yourself -- what you want to know is contained in the first 5 to 10 pages. Since most people worry about the long-term trend, and where things are going, I've taken data from the report's tables and put them into easy to understand time-series graphs, broken down by race and ethnicity. I'll then address a few of the larger issues.

All birth rates are live births per 1000 women in a given group. I'll only look at births to 15 - 17 year-olds because mothers younger than that are even rarer, and people freak out less about mothers at or above the age of majority. The 18 - 19 graphs look similar, and you can create them yourselves using the NCHS' report and Excel. Update: see the end of the post for the one 18 - 19 year-old graph that is different, which shows birth rates among Hispanic 18 - 19 year-olds increasing since 2000. [End update]

Most of the recent increase is due to 18 - 19 year-old births, so that's another reason not to care about an increase in "teen pregnancy" -- 18 and 19 year-olds are adults. Moreover, there is an increase across all age groups, especially 20 - 24. So, there's nothing special about teens of any age -- the 15 - 17 year-olds increased a bit, while the 18 and 19 year-olds appear to really be part of a larger group of 18 to 24 year-olds. (Nature doesn't adhere to our numbering system, where there's a bright line between 19 and 20.) Births are just up overall, and the closer we get to the female fecundity peak in the early 20s, the stronger the signal is.

First, the NCHS has data going back to 1970, although it is not broken down by race. Still, here is that graph:

There is a downward trend throughout, with a steady oscillation around that trend. So, the rate will probably continue to decline into the following decades, and we shouldn't be fooled by a temporary increase. For the near future, it looks like the rate will remain pretty flat for about 5 years, then start to increase again, with a decrease again after that, all on a downward trend.

Next, the data with race broken down begins in 1980 and includes White, Black, Asian / Pacific Islander, and American Indian / Alaskan Native. The graph with Hispanic ethnicity is further down. Here are the birth rates for Blacks and AIANs, and for Whites and Asians:

Since the graphs look so similar to the all-race graph, we can assume that from 1970 - '79, the birth rate declined across all races. Again, we see a downward trend with a steady oscillation around it. In no case is the 2006 uptick dramatic, and it looks just like it does in the all-races graph. So again, the rates will probably remain mostly flat for the next 5 years, increase, then decrease, following the overall downward trend.

Finally, the data on Hispanic and non-Hispanic groups starts only in 1990. Here are the trends:

The patterns are the same as in the other graphs, so it wouldn't be too risky to assume that, if we had the actual data, they'd look like they do in the first graph back to 1970. There are clear race and ethnic differences -- the Black line is always above the White line -- but the downward trend and presence of oscillations does not have to do with race or ethnicity. Whatever causes them is at a societal level. The only interesting difference in these Hispanic graphs is that non-Hispanic Blacks and Hispanics have switched in the rank order: we now have more of a Hispanic problem than a Black problem.

That should give people a clearer idea of what is going on. It's silly to forecast based on two data-points -- last year and this year -- when there is plenty of other data to help out. The reason people do this is because it allows them to indulge their desire to imagine the end of the world. The slightest aberration or reversal of a reassuring trend is greeted with exhilaration by the declinist junkies -- "So there's hope that the world is doomed after all!"

Furthermore, these data are all on birth rates, not pregnancy rates. We won't know what the teen pregnancy rate was until we have abortion data, and the NCHS says that won't be for awhile. (The most recent data are from 2004.) For all we know, pregnancy rates are the same or lower than before, but more of those who do get pregnant may opt to keep the kid.

I suspect something like that is true based on adolescent sex behavior data that I've already written about. All measures of sluttiness among teenage girls -- having sex at all, having 4+ partners, not using a condom, etc. -- have declined from 1991 to 2007. Indeed, there is no change in any of the measures from 2005 to 2007. See here for the data from the YRBS. This suggets that the 2006 uptick in birth rates was not due to greater rates of bad behavior among teenagers, but to a greater aversion to abortion among today's young people.

A statement by the National Campaign to Prevent Teen and Unplanned Pregnancy hopes for the worst about these YRBS data:

For teens in school, YRBS data for 2005 and 2007 reflected small increases in sexual activity and decreases in contraceptive use that were not statistically significant, but the changes are likely large enough to account for the 3% increase in the teen birth rate (and likely a similar increase in the teen pregnancy rate) between 2005 and 2006.

The part that I've boldfaced is mostly a lie. If you look at the YRBS data in the link above, there is an apparent but non-significant increase of 1.0% in the percent who have had sex, from 2005 to 2007. However, there was also an apparent increase of 1.1% from 2001 to 2003, and of 1.5% from 1997 to 1999 -- greater than the most recent apparent increase, yet which resulted in no uptick in teen births. As for percent who are currently sexually active, there is an apparent but non-significant increase of 1.1% from 2005 to 2007 -- but there were similar increases from 2001 to 2003 (up 0.9%) and 1997 to 1999 (up 1.5%). The same is true for percent who use birth control pills. Only the percent who used a condom the last time they had sex shows an apparent and non-significant decrease that isn't matched by similar apparent decreases in previous years. Again, though, the change is not significant.

Here's what the CEO of the National Campaign told USA Today:

Sarah Brown, CEO of the National Campaign to Prevent Teen and Unplanned Pregnancy, says she is less inclined to believe abortion is driving higher teen birth rates and suggests that increases in high-profile unmarried births in Hollywood, movies and even politics is a significant factor for impressionable teens.

"In the last couple of years, we had Jamie Lynn Spears. We had Juno and we had Bristol Palin. Those three were in 2007 and 2008 and not in 2005 to 2006, but they point to that phenomenon," she says.

You have to admire her candor and pity her desperation: she admits that the purported causes came years after the effect. So, rather than Hollywood influencing a social trend, the already existing social trend began to reach even into Hollywood. After that happens, there may be positive feedback, but let's be clear about who started it. In general, Hollywood doesn't want to influence any social trend -- they want to figure out what the existing trends are and pander to them to get rich. They're greedy capitalists, not mad scientists.

When I am elected dictator, my first campaign to improve the people's mental health will be to censor anyone who, in a mainstream forum, argues that 1) Hollywood is responsible for degrading our morals, 2) poverty causes crime, 3) "it's the parents' fault," or 4) these kids these days don't know what good music is. Ah, to read the newspaper without feeling the urge to strangle 5 of the 6 people quoted -- that oughtta make everyone feel a bit more sane.

Note: here's the graph for non-Hispanic Black and Hispanic 18 - 19 year-olds:

So as with the 15 - 17 year-old case, Hispanics have overtaken Blacks, and also that their rate has been increasing since 2000. This is the only worrisome data -- and yet another reason to slam our borders shut to anyone who didn't graduate college.

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Monday, December 15, 2008

Do women lighten their hair to compensate for aging?   posted by agnostic @ 12/15/2008 02:17:00 AM

In Jason's post on the distributions of hair and eye color, it looks like women are claiming their hair is lighter than it is. The sex differences are the opposite of what is found when the hair is rated by others. Women are lying because they think it makes them look better.

If they're going to misrepresent their hair color, they're likely to dye it for the same reason. Whether it is to participate in the fashion for blonds in their age cohort or to cater to men in their cohort (there's evidence that younger audiences aren't as captivated by light hair), older women should lighten their hair more. It's like a boob job.

I compared age and hair color data from Playboy Playmates of the Month. I only distinguish between blonds and non-blonds (though there are a few tough calls who I label intermediate). I can't look at age by year since some years have few points. I've grouped the playmates into three ranges: 16 - 20 (n = 210), 21 - 24 (n = 329), and 25 - 35 (n = 105). I chose these groups since each has lots of points. I had to include everyone 25+ in one group, or statistical tests could not have been done.

In any case, these groups also correspond pretty nicely to three phases of a female's reproductive career: 1) the high school or college girl who doesn't have to try at all to look presentable; 2) the early-mid 20-something whose waistline has begun expanding; and 3) the 25+ woman who should have had a child. Here is how the female body shape changes across the lifespan.

So here is a plot of the proportion of each age group that is blond, along with 1 standard error on either side:

The youngest group (where blonds are 42.1%) is statistically significantly different from the oldest group (where blonds are 53.7%), and marginally significantly different from the middle group (where blonds are 48.3%). The middle and oldest groups are not significantly different. (See Appendix for the gory details.)

I conclude that the 16 - 20 year-old playmates had such flawless and tight skin, clear large eyes, gravity-defying breasts and buttocks, etc., that blond hair wouldn't add much. Already by their mid-20s, women's looks have just passed their peak, so that they're probably more likely to dye their hair, although the difference may be illusory. But certainly by 25, the rest of their face and body couldn't compete with those of younger girls, so they begin dying their hair blond to distract the audience from that. (Getting fake boobs would probably show a similar age-related trend.) It's like how restaurants scam the elites by making shitty chicken sandwiches but then tossing on a bit of pesto to make it seem exotic and totally worth $15.

There's another prediction of this idea: if playmates were to be drawn increasingly from older women, they should become blonder too. I've shown that the average playmate has gotten older since a low during most of the 1960s, and in the second link in this post I show that they've also gotten blonder. Indeed, the Spearman rank correlation between a year's average age and average blondness of playmates is +0.35, two-tailed p = 0.006. Taken as a whole, these differences suggest that, even if it isn't as strongly related to aging as is buying moisturizers and skin-firming lotions, lightening the hair is one way that aging women cope with their declining attractiveness.

But if blond hair enhanced attractiveness to the same degree across all ages, then age would not predict the percent of women who dye their hair -- younger girls would do so just as eagerly, as with washing and styling their hair in the morning (a huge boost over a rat's nest). It seems, then, that blondness yields diminishing returns in attractiveness -- I mean, you can't really picture teen star Selena Gomez having to dye her hair. Or for that matter Audrey Hepburn, Jean Shrimpton, Penelope Cruz, or Monica Bellucci bleaching their hair at any age!


I ran an F-test for equality of variances between two samples, one test for each pairwise comparison. None of the three groups had significantly different variances. I then ran a two-proportion z-test (equal variances), one test for each pairwise comparison. The p-values for the tests are: 0.080 (youngest vs. middle), 0.025 (youngest vs. oldest), and 0.164 (middle vs. oldest). These are one-tailed because the prediction was that increasing age should increase the percent who dye their hair or need blond hair to make up for having less attractive skin, breasts, etc. It's like expecting the percent of women with fake boobs and facelift surgery to increase as age increases.

But I made three comparisons, and the more comparisons you make, the more likely you are to find apparently low p-values just by chance. No one really knows how to deal with adjusting the critical p-value (alpha) when you're making multiple comparisons. So rather than futz around with the many theoretical corrections to alpha, I decided to take an empirical attack.

I wrote a program in Python that took all the playmates and separated them into three groups, each one having the same size as the three groups I created based on age. But instead of deterministically using age to sort them, I sampled them at random without replacement to fill the first group, then the second group, with the rest going into the third. Because "group 1," "group 2," and "group 3" were formed randomly, the proportion of blonds shouldn't be too different between them. I performed the same two-proportion z-test (equal variances) as before, one for each pairwise comparison.

I simulated this process 10,000 times, and then took the fraction across all runs that the z-statistic was at least as large as the observed z-statistic, doing so for each of the three group comparisons. These empirical p-values are: 0.0813 (youngest vs. middle), 0.0226 (youngest vs. oldest), and 0.1564 (middle vs. oldest). Therefore, in this case, correcting alpha for multiple comparisons would have been pointless, perhaps because I only made three rather than three thousand comparisons.

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Thursday, August 14, 2008

Has porn become mainstream? Not really   posted by agnostic @ 8/14/2008 04:04:00 AM

A rumor I've been hearing a lot lately, although I recall hearing it as early as 2003, is that "porn is becoming / has become mainstream" -- or that it's ubiquitous, unavoidable, the wallpaper of our culture. Like most alarmist ideas spread by the innumerate -- failing schools, oral sex rampant among teenagers, the coming Islamic Caliphate -- I assume it is a gross exaggeration or false. And as always, I'm right. It doesn't take a genius: simply judge based on the track record of similar panics made possible by mass media, going back to the witch hysterias of Early Modern Europe.

I collected a bunch of data about a month ago and planned on doing some time series analysis, maybe showing how certain models (like epidemics or logistic growth) would fit the data, but the fall semester begins soon, and I'm preparing enough as it is. So nuts to the analysis; I'll just present the data, since the picture is very clear. In brief, the popularity of pornographic movies has remained steady for over 20 years, and in a sense for the last 35 years -- when the data begin. The popularity of print pornography fell sharply after its peak in the early/mid 1970s and has more slowly declined for about the past 20 years. Even non-pornographic but racy "lad mags" have seen their popularity tank, with only Maxim US holding steady.

Before getting to the data, though, how far back does the "porn has become mainstream" meme go? I didn't conduct an exhaustive search, but I found a 1990 letter-to-the-editor in the NYT, as well as a 1998 news story in Time, so it's hardly new. It's interesting to note that most such articles feature a quote like this one from New York Magazine in 2003:

Over beers recently, a 26-year-old businessman friend shocked me by casually remarking, "Dude, all of my friends are so obsessed with Internet porn that they can't sleep with their girlfriends unless they act like porn stars."

The grave implication is: "Just think of what young people who grow up with this will expect!" But a moment's reflection tells us that the same is true of men who visit prostitutes, who've been around forever. And yet men haven't come to expect their wives to behave like wild whores inside or outside the bedroom -- again, except for the handful of 20-something losers who New York Magazine manages to mine such embarrassing quotes from. Indeed, the universal Madonna / Whore dichotomy tells us that most men will continue to prefer their flings to act like call girls, pornstars, strippers, etc., while preferring their gfs and wives to act not whorish.

Enough gasbaggery; onto the data (and then more hot air). The "porn is everywhere" meme claims that a high percentage of people are infected by porn, whether through video or print. Obviously the claim is not that there's a lot of porn out there, but which no one ever consumes -- so we just look at the prevalence of porn-watchers over time. Fortunately, the General Social Survey, a large and representative national survey, asks Americans if they've watched an X-rated movie in the past year. To see for yourself, go here and type in, without quotes, "xmovie" in the row box and "year" in the column box. If you want to see male vs. female, type "sex(1)" for male or "sex(2)" for female into the selection filter box. Across the years, the response rate is 58%, from about 51,000 people -- damn good for surveys. Here are the results for men and women (click on the image to see it full-size):

For men, porn-watching declined at least from 1973 until 1980, and increased until 1987. After that, you may be able to see fluctuations up and down but they're around a pretty steady value of about 35%. The pattern for women is much clearer to see: essentially no trend, but cycles of varying period and amplitude. I interpret these patterns as a decline during the 1970s when porn theaters became unfashionable, an increase during the 1980s as porn became available on VHS, and no change afterward -- in particular, no skyrocket due to the availability of internet porn, something I would not have predicted by intuition.

Also bear in mind that if porn were indeed "becoming more mainstream," we should see a strong upward trend just because people are less embarrassed to admit they watch it. Only if people in the 1970s were hooked up to porn 24 hours a day but denying it, while people today admit to it at the same rate but are watching less, would we observe a lack of a strong upward trend. Even in that case, that means porn-watching was more prevalent in the past. I favor a simpler interpretation: that because porn has not become mainstream, nor more taboo, people tell the truth at the same rates from the sexually liberated 1970s up to today.

There are of course liars, but they don't seem concentrated in one period or another. How bad is the lying in any period, though? -- maybe all men are watching porn now but only 35% admit it. In 2003, the Nielsen Ratings people tracked the traffic of internet porn sites, and they found that 1 in 4 internet users visits porn sites (see here). That's just what we'd expect from the GSS results, which show that of men and women combined, 24% in 2002 and 26% in 2004 watched porn. Traffic doesn't lie, and because the numbers are virtually identical to what people say, we conclude that almost nobody lies about watching porn (at least in anonymous surveys). So not only have their proportions not increased relative to before, but porn-watchers are not even a majority of men -- a bit more than one-third. For women, even less so -- about one-sixth. Porn is not now, and never was, mainstream.

Turning to porn in print, I collected circulation data for Playboy for any year I could find. The data are from many sources -- business sections of newspapers, histories of the magazine, etc. -- and for some years I couldn't find estimates. Still, there are plenty to see a clear pattern. I did the same for Maxim's US edition, both shown here:

Playboy accelerated in popularity from its beginning in 1953 to 1973, after which it plummets until 1987, and then it slowly but steadily declines to today. I don't have rich data to show it, but from what I read in my research, the same rough pattern holds for other porn magazines like Penthouse and Hustler. Maxim looks like it's grown logistically, on analogy with a fad growing by word-of-mouth contagion. Maxim of course is not porn; the nearest thing might be 1940s pin-ups. I speculate that Playboy's exponential growth was due to featuring young brunette girl-next-door types, and its crash due to using blonder and older "power bitch" types. Maxim has done well, in this view, for relying so heavily on dark-haired women. In any event, we see that porn has not become mainstream in print either -- just the opposite.

One last batch of data mostly from the UK, home of the "lad mag." Almost as soon as the fad had begun, it peaked and began plummeting, which has been well covered in the British press. I've shown it here for three of the most popular UK lad mags (I culled the data from various newspaper or other reports):

The US edition of FHM appeared to be doing well, even if it had begun to saturate. The drop-off I drew to show that it was abruptly canceled and only exists as a website now. Stuff Magazine, also once popular in the US, was cancelled in 2007. So even the non-porn but racy lad mags are dying off, save Maxim US.

Because the "porn has become mainstream" meme is part of a panic -- either about eroding cultural standards, eroding barriers between public and private vis-a-vis sex, eroding relations between men and women due to unrealistic expectations, or the erosion of something else -- most of those who already believe it will not be persuaded by the stark clarity of the data here. (Hopefully the open-minded ones will end up reading this.) Like witch-hunters, they will shift the goalposts perhaps by saying, "Well yeah, but that just means that porn's influence is more subtle and covert, but no less pervasive and corrupting because of that."

The first target will be female appearance, of course: as porn becomes more ubiquitous, they start dressing like sluts! Except that porn-watching increased most dramatically and reached a peak during the '80s -- the decade of high-waisted pants, granny-panties, and bulky manlike tops (baggy sweaters, shoulder-pads, etc.). I've written elsewhere about how girls don't even dress like sluts anymore, a 5-year fad in thongs notwithstanding.

The second target will be sexual behavior: as porn becomes more ubiquitous, people will begin acting more promiscuously. But I've already shown that there was probably a single increase and single decrease in promiscuity, with the turning point around 1991. The popularity of porn either waxes and wanes for women or dips, increases and stays for men -- it has nothing to do with how promiscuous people are.

Anyway, I could go on, but you get the idea. Let's all be done with this "porn has become mainstream" nonsense.

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Tuesday, August 12, 2008

Attractiveness: logarithmically perceived, normally distributed, sought for genetic benefits   posted by agnostic @ 8/12/2008 02:46:00 AM

Our intuition of space and time is to perceive them logarithmically: we place a bunch of tick-marks near "here" and "now," and only measure orders of magnitude as we move outward. The linear scale used by scientists places a tick-mark at evenly spaced intervals. For example, between "here" and 100 miles away, humans may have a bunch of words for nearby distances -- "right here right here," "right here," "heeeeere," "here," and "there" -- while we would represent the majority of the distance that is not near with a few words, such as "theeeeere," "over there," "way over there," "way way over there," etc. Ditto for time. John Hawks reviewed a recent study, which itself contains many references, er, right here right here.

I think we perceive physical attractiveness in the same way. (Although quick Googling didn't turn up anything, I'd be surprised if this idea were original -- at least, it's not a common idea.) The reason is the same as the above: when we use something like the popular "1 to 10" ratings, we seem to finely slice up the attractiveness space near the "good-looking" end and place tick-marks increasingly farther apart as we move farther away, like this:

Just think about it -- have you ever split hairs over how incredibly ugly a person was, like 1 vs. 2? Probably you have never done so, but I'll bet you and your friends get into regular arguments about whether Jessica Alba, or anyone else like her, is an 8.5, 9, or 9.5. You probably save the "1" from the "1 to 10" scale only for the most distant monsters, humanoids so freakish you could not expect to reach them in a dozen lifetimes. And anyone in a large vicinity of that spot would be compressed into the "1" category.

Why do we make these compressions -- why not keep the fine structure of the space, like rate people from 1 to 1 million? Because we have limited vocabularies and cognitive resources, and because not all regions of the space are as attention-worthy as others for surviving and reproducing. We care a lot about what's going on near us because the goings-on of the other side of the world, until very recently, had no bearing on our survival and reproduction. The same is true for time: until very recently, the very long run did not matter at all, so why bother measuring the next millenium in yearly intervals? Only the somewhat near future has mattered.

Continuing the analogy, then, it must be that it has been the good-looking rather than the ugly people who have been most worthy of our attention during our evolution, since that's where the density of tick-marks is greatest. That is not a tautology. Indeed, the great evolutionary biologist William Hamilton had an idea that probably is too crazy to be true -- that animals pay attention to attractiveness in order to avoid getting infected by parasites while mating, attractiveness signaling the mate's parasite-free status and ugliness signaling their being bug-ridden.

But if that were true for humans (and I'm only talking about us now), then we would finely slice up the attractiveness space near the ugly end, reflecting our worry of getting infected: "definitely swimming in bugs," "pretty buggy," "buggy enough that I'll be scarred for life," "buggy but I won't be too compromised by sleeping with them," "low bugginess," etc., and compress the vast expanse of attractive people into a few categories like "probably not buggy" and "definitely safe."

So, it doesn't look like we avoid the ugly but that we pursue the attractive, and that jibes better with the alternatives to Hamilton's "parasite avoidance" hypothesis, namely the genetic hypotheses. First is Alfred Russell Wallace's "good genes" hypothesis: we pursue good-looking people because their good looks signal having genes that have protected them against the ravages of pathogens, or whatever else may damage their health. And second is R.A. Fisher's "sexy sons" hypothesis: we pursue good-looking people because, whether we find them good-looking or not, the potential mates of our offspring will, so we'd improve their reproductive success by giving them genes for attractiveness. The idea that attractiveness is logarithmically perceived doesn't decide between these two genetic theories, but I think it does go against the "parasite avoidance" hypothesis.

Last, I used to think that attractiveness was lognormally distributed -- that, due to the synergistic effects of different body parts, most people are ugly, and only a handful are good-looking. (And anyone who says otherwise is being polite, fooling themselves, or not looking at a broad spectrum of human beings.) However, that's just based on my perception -- perhaps attractiveness really is normally distributed. If our mind re-scales attractiveness using logarithms, then it will transform a normal into a lognormal distribution too.

Normally distributed traits suggest an additive genetic basis, whereby small effects across a large number of loci are added together to determine the phenotype.* A lognormally distributed trait, such as "genius" in the sense of "eminence in the arts and sciences," has low heritability. The reason isn't relevant here; what's important is that we wouldn't expect a lognormally distributed trait to have a mostly additive genetic basis.

But the one study that estimated the heritability of attractiveness, McGovern et al. (1996), found that the monozygous concordance rate was virtually twice the dizygous rate (0.65 vs. 0.33, respectively), and that means that the genetic variance in the trait is almost entirely additive. So the quantitative genetic evidence fits into the bigger picture of a normally distributed trait in reality, but which the human mind transforms logarithmically.

I can't do any empirical tests like those in the study that John Hawks reviewed because we haven't yet found an objective way to measure attractiveness. I don't just mean that we can't trust what people say -- even if you measured a person's attractiveness by taking the average level of physiological arousal from subjects who viewed the person's picture, that still is a reflection of the subjects' perception. However, I'm more of a theorist than an experimentalist, so maybe a clever doohicky-rigger out there can think of something better. If they do, the prediction is that true attractiveness can be measured on a linear scale just like time and space, and that on this scale, humans would place their "1 to 10" tick-marks in a logarithmic spacing, as in the earlier picture, the same way that innumerate tribes do with their number words.

* This is unlike, for example, eye color, where only a few genes make most of the difference, and where eye color is mostly a recessive trait. That is, most people have dark eyes and only a few have light eyes -- whereas a normal distribution of eye color would show most having green and equal, smaller numbers having blue or brown.

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Sunday, July 06, 2008

Maxim's audience prefers brunettes; distribution is bimodal   posted by agnostic @ 7/06/2008 03:10:00 PM

While showing that the super-popularity of blonds is recent, I saw an apparent reversal of the upward trend around 2000, suggesting that perhaps Playboy readers are becoming fatigued by blonds. To get a better feel for what the younger generations prefer, let's look at Maxim magazine (US edition), whose average reader is 27.5 years old (by contrast, the average Playboy reader is 32.5). Maxim is the contemporary counterpart to Playboy -- it's widespread on college campuses, and is what horny dudes are likely to leaf through to ogle hot babes. They also have roughly the same circulation -- about 2.5 million. For those in a rush, I've boldfaced all key results.

Audacious Epigone and I have both done analyses on the Maxim Hot 100 lists for recent years (see here and here). But these smell of "lists just for the fun of making lists" or "lists to get people arguing," and the fact that A.E.'s results and mine varied so much despite analyzing consecutive years supports that idea. However, there are at least two datasets that are surely more shaped by audience demand than the editors' whims: the girls who appear on the cover to lure the reader into purchasing it (they are featured prominently inside as well), and the girls who readers vote as being the hottest out of a pool of "Hometown Hotties" nominees.

First, I looked at all covers of Maxim from 1997 to present, excluding only two issues that did not show people, which yielded 126 covers. To be more fine-grained than before, I coded hair color as 1 = light blond, 2 = dark blond, 3 = light brown, 4 = dark brown, and set aside 0 for redheads. If there were multiple girls on a cover, or if an issue had multiple covers available, I took the average of all girls for that issue. For a few, it was too close to call, so I coded the girl halfway between two categories. If the cover was ambiguous, I looked at the full photo shoot through a Google Images search. There was no significant trend in blondness over the past 11 years.

To determine the average hair color, I re-coded redheads as 2.5 (there were only 2 of 126, so this choice doesn't really make a difference). The average Maxim cover girl scores 2.8 -- light brown. To determine the frequency distribution, I binned girls into light blond, dark blond, light brown, and dark brown, with redheads going into the light brown bin. Some data-points were not integers, so I used both conventions for rounding the numbers with .5 ("up" and "down"). It turned out to make almost no difference.
Here is the distribution using "rounding up":

Light blonds and dark browns are overrepresented, while the intermediate colors are underrepresented. To test this, I used published data on hair color frequencies and took the Dutch values instead of the Icelandic ones, since Americans must resemble the former more than the latter. Because the published estimates have only one intermediate category, I had to merge the dark blond and light brown categories together. I put redheads in the intermediate category since otherwise I wouldn't be able to do a chi-squared test (an expected number would be too small). For rounding up, chi-squared = 24.1 (p less than 0.0001, df = 2); and for rounding down, chi-squared = 27.4 (p less than 0.0001, df = 2). So, the discrepancy between Maxim cover girls and the general population is no fluke.

But are light blonds and dark browns equally overrepresented? No: depending on the rounding convention, light blonds are 25-29% more common than we'd expect, whereas dark browns are 63-66% more common than we'd expect. Together with the average cover girl being light brown, I conclude that Maxim readers respond more to women with dark hair, although there is a sizable minority that prefers light hair.

Second, I did a similar analysis on the finalists in Maxim's Hometown Hotties contest from 2003 to 2007. For 10 weeks each year, Maxim staffers scour the country to photograph 100 local hotties per week. Of these 100, Maxim readers vote online to determine 10 semi-finalists and 1 finalist for that week. There is no way I'm looking through 5000 pictures to see what all the contestants look like, and the 5 winners are too small of a sample. The 50 finalists seem like enough data to get a good picture. (Someone else can analyze all 500 semi-finalists.) Indeed, the results are virtually identical to the cover girl results, which shows that both datasets are reliably measuring the same thing. The methods are as before.
Here is the distribution of hair types among Hometown Hotties finalists:

Once more, light blonds and dark browns are overrepresented, while intermediate colors are underrepresented. For rounding up, chi-squared = 10.3 (p = 0.0058, df = 2); for rounding down, chi-squared = 13.1 (p = 0.0014, df = 2). These results are no fluke. As before, though, dark browns are more overrepresented than light blonds: by 57-64% compared to 22-52%, respectively, depending on the rounding convention. (The convention for rounding didn't make much of a difference overall in these data either, but since the sample size is less than half that of the cover girl data, it introduces more uncertainty.) Replicating the cover girl results, the average Hometown Hotties finalist scores 2.8 -- light brown. I conclude what I did in the cover girl case.

To see how closely the two datasets agree with each other, I did a chi-squared test for the observed values in one, using the other's frequencies as the expected ones. Taking the cover girl frequencies as expected, the hometown hotties data are no different (chi-squared = 0.025, p = 0.9875, df = 2). The same holds for the other way around (chi-squared = 0.068, p = 0.9666, df = 2). That is for rounding up, but rounding down produced p-values above 0.5 as well. I conclude that both datasets measure the same thing -- audience preferences.

As a final anecdote in support of the bigger picture, consider the Miss Maxim girls. Although about 1/2 of the 24 countries could have easily supplied a blond, only 1/6 actually did. The girls from Belgium, England, and so on, look quite different from the average Belgian, Englishwoman, etc. Clearly, among Maxim's horndog audience, dark hair rules.

What is causing these two key results -- that Maxim readers prefer brunettes, and that the distribution is bimodal? I think brunettes are just more exciting on the level of physiological arousal, so the younger -- and therefore the randier -- the audience is, the more they will prefer dark hair. When Playboy's circulation was growing exponentially in the 1960s, it featured hardly any blonds and mostly brunettes. As its average reader has become older, its Playmates have become blonder.

Lighter hair is correlated with behavioral inhibition (see here), so it could also be that dark-haired girls get the blood pumping more because they appear more flirtatious.

Or it may be a pure fashion trend -- digging blonds is what your father's generation did, so you set yourselves apart by tacking up pictures of Mila Kunis and Vanessa Minnillo on your wall.

As for the bimodal nature of the distribution, this probably reflects supply meeting demand: the audience's preferences are likely bimodal, with a majority preferring brunettes and a minority preferring blonds. Guys respond better to the exaggerated version of their tastes, and that drives up the fraction of light blonds and dark browns, in the same way that among porn stars you see an inflated fraction of women with large breasts or large rumps.

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Monday, June 30, 2008

Your generation was more into sexualizing young girls   posted by agnostic @ 6/30/2008 04:29:00 AM

Remember that better time when college coeds frolicked on the quad lawn, safe from the eyes of older males, who were drawn instead to the allure of a mature woman? Indeed, doesn't it seem like nowadays, in our Girls Gone Wild culture, we shove females into the sexual spotlight at ever younger ages? That's what you'd conclude from the 50,000 alarmist results that a Google search for "+sexualizing +young" returns, in particular the recent panic over 15 year-old Miley Cyrus posing semi-topless for Vanity Fair. The cropped picture to the left is of Elizabeth Ann Roberts, who was 16 when she was photographed nude as Playboy Playmate of the Month -- of January 1958.

On an intuitive level, though, we know that the culture must be more hostile than before to sexualizing young females -- there would be no hysteria if it were acceptable. Plus, suburban housewives and city-dwelling cougars have never hogged so much of our attention. Still, let's turn to three datasets that show the trend is, if anything, toward sexualizing increasingly older females in popular culture. We will look at data across the decades on beauty pageant winners, girls featured in nude magazines, and hardcore porn actresses.

First, take the winners of the Miss America beauty pageant, a competition determined mostly by how closely the contestant fits the ideal look of the time. A writer for the website Seduction Labs has already done an extensive analysis, so I took the age data from his work. Here is how Miss America's age has changed over the decades:

It sure looks like Miss America is getting older -- the ones from before 1940 are quite young -- and this is true: Kendall's tau for the correlation between year and age is +0.50 (p = 3 x 10^(-10), two-tailed). Admittedly, estimating the youth-obsession of each year with only one data-point -- the winner from that year -- is less desirable than averaging all contestants' ages for that year, but the data are hard enough to come by that this is the best we can do.

Next, consider the Playboy Playmates of the Month, averaged for a given year. While the 1950s had fewer data, each year still had at least 7 data-points. Using 12 data-points to estimate each year should make us more confident in the results, shown here:

Again, the average Playboy Playmate is getting older: Kendall's tau for the correlation between year and age is +0.44 (p = 3 x 10^(-6), two-tailed). The trend is clearly not linear, though, since there was a decrease in age at least from the mid-1950s, when the data begin, throughout the 1960s.

In response to a criticism brought up in the comments to the post showing that the popularity of blonds is recent, I've also calculated Kendall's tau based on the raw month-by-month data-points, rather than yearly averages: it is +0.18 (p = 1 x 10^(-10), two-tailed). As I mentioned to the commenter, I think it's more instructive to look at the year's average since the Playboy people likely have a target girl in mind for the year's subscription, based on the perceived demand. That is, the Playmates within a given year are comparable to the Miss America contestants for a given year -- they are chosen to fill out a year's run, and Miss April could just as well have been Miss December. Still, even by this perhaps overly stringent standard, the trend is positive and significant.

Finally, we look at actresses in hardcore porn movies. Collecting a representative sample of active females in a given year would be incredibly arduous, so instead I took famous actresses and determined how old they were when they made their first movie, and entered this as a data-point for the year in which they started making movies.

The lists I used are the AVN Hall of Fame, the XRCO Hall of Fame (which barely added anyone else), and a list of female porn stars by decade drawn up by the porn geeks at Wikipedia. I required each year to have at least 5 data-points; if there were too few, I merged that year's data with an adjacent year (whichever had fewer data-points than the other choice), so that the data-sparse year is excluded and the beefed-up year is included. This mostly affects the 1970s and early 1980s. Here are the ages of first-time porn stars by year of their first movie:

There is no increase or decrease over time: Kendall's tau for the correlation between year and age is nowhere near significance. There are several apparent upward and downward trends, though. This might be the only example of the 1980s and early 1990s showing greater progress by the declinists' standards. I recently analyzed a large, representative sample of porn stars and found that their average age is 23, for what it's worth. Again, that's what we really want to see: the age of the typical actress for a given year.

Maybe girls enter at earlier ages in recent times but don't reach their peak in popularity until they are in their early 20s. Another drawback of looking at age at first movie is that it ignores the recent popularity of "MILF" actresses -- maybe it's just that the variance in age is increasing. Admittedly, these pornstar data are not ideal.

Finally, we examine the popularity of beauty pageants specifically for teenage contestants. While I don't have datasets to analyze, such as the annual TV ratings, there is enough information on them to get a rough picture. First, there is Miss Teen USA, the adolescent version of Miss Universe. It was created in 1983, reached its peak for ratings in 1988, and has declined in popularity afterward, to the point where it may not even be televised anymore. And second, there is Miss Teenage America, which was created in 1962 and was last televised in 1977. Judging by its corporate sponsorship and celebrity hosts, it must have been somewhat popular. There are other beauty pageants for teenagers, but they are not even televised, and so do not count as evidence of an obsession with youth. Rather, we see a shift away from throwing young girls into the purely sexual spotlight.

Since there are no huge long-term swings up and down in these data, as opposed to the cases of sluttiness and violence, all generations can say that they've improved over previous generations, or at least done no worse. If any generation is to be accused of sexualizing younger girls in popular culture, though, it is surely the older ones. It is true that the current culture does not value women over 30, but that has never been the case -- just the opposite.

As with sluttiness, part of the declinists' misperception may be due to fashion trends, such as even prepubescent girls wearing adult-inspired clothing. That's hardly evidence of their being sexualized, though -- no guy is actually looking at them as a sex object, and dressing like an adult doesn't make you behave like one sexually. While it may be a bizarre fashion trend -- though more bizarre than when pre-pubescents started wearing two-piece bathing suits? -- it doesn't reflect a sexualization of the young.

What's causing this trend toward older sex symbols? Oh, I don't know, but I'm sure we'll get a bunch of half-baked ideas in the comments, so I'll get the goofball ball rolling. Women are having their first kid later, if at all, so there's a wider age range of females who haven't ruined their figure by giving birth. Still, according to the analysis of Miss America winners at Seduction Labs, there are other trends: starting around 1960, winners became taller, less buxom, and less hourglass in shape, in addition to older. In short, the feminine ideal in popular culture has been worn down by the march of the masculine minxes. It's a mistake to blame this on the women's movement of the 1970s, though, since most of these trends began in the early-to-mid-1960s. Radical feminists were just jumping on the bandwagon and trying to steal credit for it.

Though it's harder to measure, the manliness of these sex symbols' faces has surely increased -- go back and look at some of the Playboy Playmates from the late 1950s through the late 1960s. They look like girls, not butch transvestites (NSFW, obviously). I see this as a form of cultural decline, of course, but the declinists who decry our obsession with youth could not be more wrong.

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Sunday, June 29, 2008

Bygone brunette beauty: Fashion in hair color   posted by agnostic @ 6/29/2008 05:12:00 AM

Long-time readers know that one of my beliefs that I'll stop at nothing to prove is that blond women are not sexier than brunettes, whatever other appeal they obviously have for many men. Point-estimates of the current popularity of blond hair neglect the fact that standards of beauty can change over time -- within boundaries, to be sure, but still. Perhaps we only live in a blond-obsessed world today, while brunettes may have ruled in the past. Indeed, I will show just that. Furthermore, the shift toward blonds parallels several other shifts toward a more masculine ideal of female beauty since the early / mid-1960s.

The data come from Playboy Playmates of the Month ("Playmates") from 1954 to 2007. We need to look at sources that pander to popular demand in sexual tastes, which excludes runway fashion magazines (not used by males for fantasy purposes) as well as data on high-ranking Hollywood actresses (who are esteemed only in part based on their looks). We also need comparable data that stretch over decades, and that provide us with many data-points for each year -- in a worst case scenario, we might look at something like Miss Universe winners, but estimating the value of blond-obsession for a given year with only a single data-point is hardly ideal. Playmates, though, yield 12 data-points per year.

In the name of scientific discovery, I looked at pictures of every Playmate [1], and coded her hair color as either 1 for blond or 0 for non-blond. Dark blonds counted as blond, light browns as non-blond. Redheads counted as blond if they had very fair, strawberry blond hair, and as non-blond otherwise. The point is not to measure the popularity of the full spectrum of hair colors -- just blondness. A small handful of Playmates had several hair colors within the single issue they appeared in. I coded these as 0.5 because their pictures were split pretty evenly between blond and non-blond hair -- maybe due to wigs, I don't know.

I then took the fraction of blonds in a given year and plotted these over time. Here is the raw scatter-plot, together with 3-year and 7-year moving averages that smooth it out:

The scatter-plot suggests an increasing trend, and this is true: Kendall's tau for the correlation between year and percent blond is +0.27 (p = 0.01, two-tailed). [2] However, because each year's value can only take on roughly 12 values (1 / 12, 2 / 12, etc.), there are a lot of tied years, which may underestimate the true correlation. Kendall's tau for the correlation between year and the 3-year moving average of percent blond is +0.47 (p = 2 x 10^(-6), two-tailed), and is +0.64 (p = 2 x 10^(-10), two-tailed) when the 7-year moving averages are used. Using a moving average gives us a better idea since they can take on far many more values, and so produce fewer ties.

Whichever one we choose, it is clear that blonds have increased quite a bit in popularity over the decades. At the same time, the trend is clearly not linear: there is a decrease in blond-obsession at least from the mid-1950s, when the data begin, to the early / mid-1960s. There follows an increase, and an apparent reversal since the turn of the millennium -- please god, let it be so. This looks periodic, like a fashion cycle.

In trying to account for this trend, we should try to be as general as possible. What other trends in female beauty show an increase after the early 1960s? I didn't look at other aspects of the Playmates, but someone else has tabulated data on Playmates of the Year from 1960 to 2006 -- again, estimating the popularity of some trait in a given year based on a single data-point is worst-case, but I'm relying on it here because I've already spent enough time collecting hair color data. The links in footnote 1 provide all the anthropometric data, though, so if you want to collect an analyze it, we will link to your analysis.

I calculated the Waist-to-Hip Ratio and BMI of Playmates of the Year from the above data, and Kendall's tau for the correlation between year and WHR is +0.53 (p = 4 x 10^(-7), two-tailed), while between year and BMI it is -0.24 (p = 0.02, two-tailed). So, these sex symbols are increasingly losing their feminine hourglass shape and fatty softness -- nearly all BMI points are below 20, so it's not like they used to be fat but are now healthy. They are also getting taller: Kendall's tau is +0.31 (p = 0.004); and smaller in the chest: Kendall's tau is -0.35 (p = 0.001).

Someone else has also done an analysis of Miss America winners, and the exact same trends emerge there as well (see his graphs).

The common factor of all these trends is that the ideal of female beauty has become increasingly masculinized. Recall that males are more likely to be blond, so the hair color trend is part of the larger masculinizing trend. I didn't look at eye color, but if it's part of the overall trend, the earlier Playmates should be less blue-eyed than later ones, as blue eyes are also more typical of males. Skin color would be tougher to analyze; if it's part of the same trend, it should get darker over time. Anecdotally, these two guesses seem to be true, but someone should look at the data to check.

It therefore appears that a preference for blonds should also correlate with a preference for taller and less curvy women. Again, someone else can look that up in the psychology literature and post in the comments. But the words "tall," "thin," and "blond" usually co-occur, don't they? Whatever appeal such women have, raw sex appeal is unlikely to be among the top reasons. Blond hair correlates with something like introversion, and that makes sense since men on average are more introverted than women. So, maybe guys start digging blonds when they become more marriage-minded, or if they are inveterate monogamists. A blond will be less likely to be bouncing off the walls and being constantly out and about in search of social stimulation.

Bang a brunette, bank on a blond? It would fit with the trend toward lower sluttiness in recent times, which we expect to weed out the sex kitten types from popular culture. This suggests that dark hair is part of that highly sexualized image -- something that was always obvious to everyone but the blond-lovers.

[1] For years 1954 to 1992, I used this source that contains the full shoot for each Playmate, and for 1993 to 2007, Playboy's official website (if the single picture available on the Playboy site was ambiguous, I did a Google image search to get a better idea).

[2] You can easily calculate Kendall's tau with this website, which I used here.

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Tuesday, June 17, 2008

Your generation was sluttier   posted by agnostic @ 6/17/2008 12:25:00 AM

I am sick of hearing Baby Boomers and Gen X-ers complain about a perceived cultural decline among the younger generations. For a variety of measures, things started to go bad already by the 1950s, became obscene during the 1960s and '70s, and plateaued some time during the 1980s. Since roughly 1990, however, things have gotten steadily better. This series will catalog such a trend for measures typically given in support of the declinist hypothesis: we begin with sexual behavior, and will eventually cover violent crime, divorce, narcissism, the arts, and whatever other examples I come across or that readers suggest in the comments. The hope is that the series will prevent the real-world picture from disappearing down the Memory Hole, as every generation thinks that patterns among its usurpers spell doom, regardless of what the data show.

Importantly, I am more interested in the slope or derivative of an indicator at some point in time, and less so in the value of the indicator at that point. The reason is simple: those who claim that our culture is declining, decaying, rotting, dying, and devolving are making an argument about whether some indicator is increasing or decreasing over time. What the declinists are really saying is that there are forces that cause promiscuity, say, to increase or to decrease. Therefore, even if some Bad Thing was lower in 1958 than in 2008, it may have been in a state of worsening then (increasing), and in a state of improving now (decreasing), so the underlying corrosive forces must have been stronger then and weaker now. It is the strength of these unseen "causes of decline" that I'm interested in.

Sluttiness is perhaps the most frequently given example of how far kids these days have fallen -- fallen, that is, from the zenith of innocence embodied by fucking your gf in the back of your car at Make-out Point (or the drive-in theater), round-robin pairing off during the sexual revolution, and the barely-covers-you costumes of the disco era and its spillover into the nightclub scene of the 1980s. Although there are not national probability samples (as opposed to convenience samples) going back decades for the entire diversity of perversions, indicators of sexual misbehavior correlate with each other, so we may need to rely on a proxy indicator if data are lacking for another.

The most straightforward indicator of sluttiness is simply the percentage of people who have had a "high" number of partners for their age. Since the declinists target the younger generations, let's look at the percentage of high schoolers who have had 4 or more sexual partners. Here are the data from the representative National Youth Risk Behavior Survey. From 1991 to 2007, this percentage has decreased. This is the strongest argument against the declinist hypothesis.

I could not find a good national probability sample that included a straightforward measure of sluttiness before 1991, but we can look at some proxies. The percentage of adolescents who have ever had sex is one: if you haven't had sex ever, you can't have had multiple partners, and earlier age of first intercourse is correlated with having more partners (that is not a tautology). The YRBS data above show that this indicator too has been decreasing from 1991 to 2007. Before then, we turn to a different dataset, although it is also national and representative: the National Survey of Family Growth. According to the CDC's summary:

Proportions were calculated for adolescent women in each year of age from 15 through 19 who reported having had premarital sexual intercourse by March 1 in 1970, 1975, 1980, 1985, and 1988. For all ages combined for each of these periods, the proportion of adolescent women who reported having had premarital sexual intercourse increased steadily (from 28.6% in 1970 to 51.5% in 1988 (Table 1)).

The 1988 figure of 51.5% is nearly the same as the 1991 figure of 50.8% from the YRBS data (see here, where the data are broken down by male vs. female). Thus, at least as far back as 1970 (and probably earlier), the fraction of teenagers who had had sex was already increasing, it peaked around 1990, and has been decreasing ever since.

We can also look at the spread of sexually transmitted diseases that are very common and have been around long enough for there to be decades of relevant data. First we look at gonorrhea. This table of gonorrhea rates by year shows that it increased from 1941 to 1946, decreased until 1957, increased until 1975, and decreased until 1997, leveling off thereafter. The main trends that emerge are a 20-year period of increase from the late 1950s until the mid-1970s, and a 20-year period of decrease from the mid-1970s to the mid-1990s.

A widespread campaign to treat gonorrhea began when the rate started to decrease, so some of the decreasing trend may be due to better medicine, but combined with the data on number of partners and virginity, some of it must also be due to lower promiscuity. In any case, the data do suggest an increasing trend in promiscuity starting in the late 1950s and lasting at least until the mid-1970s.

Next we look at type 2 herpes. Its prevalence has been decreasing since some time in the late 1990s, especially among adolescents (free full text here, popular journalism write-up here). It had been increasing at least from the mid-1970s to the mid-1990s. Because herpes is not treatable like gonorrhea is, it must be that more responsible sexual behavior has curbed its spread, again in particular among adolescents.

Taken together, these various indicators -- what percentage of teenagers have had "many" partners, what percentage has ever had sex, and what percentage has a common STD -- all argue for a period of cultural decline starting in the 1960s, perhaps as early as the late 1950s, which lasted until about 1990. Since then, however, our culture has been in a state of progress regarding teenage sluttiness. Thus, if any age cohort gets to brag about improving sexual mores, it is those born about 1975 or after.

Finally, note that the average female's appearance tells us nothing about the actual level or rate of increase/decrease in sluttiness. Because this is what most older people use to support the declinist hypothesis -- "young girls didn't used to wear thongs or jeans that low-cut when I was a boy!" -- it's worth emphasizing. Note also that more salacious dance practices among youngsters don't tell us anything real either, something I pointed out with a field study on my personal blog. Girls these days may give you a standing lapdance on the dancefloor, but -- although the male receiver may wish otherwise -- this doesn't mean she is going to fuck you. One plausible reason for the disconnect between appearance and reality is that appearances are largely driven by fashion, which changes for its own sake, rather than reflect underlying changes in preferences or behavior.


While oral sex is not worth looking at as a measure of sluttiness compared to intercourse-related indicators, it's worth mentioning that there is no "oral sex epidemic," as Oprah phrased it in a typically anti-male way. (The guys would refer to it as the "efflorescence of oral sex.") Nor is oral sex being substituted for intercourse, another worry in the mind of the declinists. Read the free pdf of the study here, or if you're lazy, a Newsweek editorial summarizing it. As is usual in these cases, the only thing that is epidemic here is a fear of an epidemic.

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Monday, June 02, 2008

Selection speculation: CLOCK and reward-dependence in Africans   posted by agnostic @ 6/02/2008 02:39:00 AM

Since so many comments lead off with some variant of "I would guess," why not try to corrall them all into one post where they could serve a purpose? Each week I'll find some area of the human genome that shows signs of recent selection, see what phenotypes the gene affects, and although I'll likely provide the most convincing story, readers can conjecture to their heart's content about what might have driven selection. It may, for once, improve the discussion to comment while still deranged from last night's drink.

Let's start with the data: using Haplotter, we see that for the gene CLOCK, there is a signal of recent selection in Africans but not in Europeans or Asians. The CLOCK gene is involved in maintaining our circadian rhythm, and I started this search looking for between-group differences in being "day people" vs. "night people." However, other genes related to circadian rhythm -- PER1, PER2, PER3, Tim, CSNK1E, Cry1, and Cry2 -- show no signals of recent selection anywhere. So perhaps there is something else that CLOCK does that these others do not.

It turns out that CLOCK is also involved in the dopaminergic system, which regulates mood and behavior. None of the OMIM entries for the other circadian rhythm genes mentions dopamine, mood, the reward system, etc. So it is more likely that CLOCK has undergone selection for its effects on mood and on the brain's reward system, rather than on circadian rhythm per se. In mice, and so potentially in humans as well, mutations in CLOCK make individuals lower in anxiety and higher in risk-taking (Roybal et al. 2007; free full text).

Turning to data from Lynn & Martin (1995), which I turned into a convenient graph here, we see that Nigerians -- the African group that HapMap data come from -- are indeed the lowest in the world in the personality trait Neuroticism (the Israeli data-point must be a mis-coding by Lynn, who is known for doing so). They are also the highest in the world in Extraversion. Neuroticism measures a tendency toward anxiety and related states, while Extraversion measures, among other things, pace of living (manics living a faster-paced life) and excitement-seeking. So Nigerians show a psychological and behavioral phenotype that's fairly comparable to the mice with mutations in CLOCK, strengthening the hypothesis that selection at CLOCK has acted on personality rather than circadian rhythm per se.

Now comes the fun part -- telling a story about why this phenotype was more advantageous in Western Africa than in Central Europe or Northeast Asia over the past 10,000 or so years. The low-anxiety and high-excitement-seeking phenotype is suspiciously like that associated with derived alleles at the DRD4 locus, and the novelty-seeking 7R allele at that locus does show up at intermediate frequencies in Africans (Chen et al. 1999; see a map here). I concur with Harpending & Cochran (2002) (free full text), who argued in the DRD4 case that the phenotype is more advantageous in "cad societies" than in "dad societies."

More concretely, I suggest, based on the teachings of the pickup artist community, that low anxiety aids in approaching more females in a shorter time -- you are less paralyzed during the approach, and you get over rejection more easily -- and that higher risk-taking motivates you to approach more females. Contingent upon having other traits that are appealing to females (a muscular body, artistic skill, dancing or singing ability, a knack for flirting, and so on), the phenotype here would have increased male success in courtship of (multiple) females, a stronger determinant of reproductive success in a "cad society" than in a "dad society."

Lastly, here are two testable predictions: 1) lowland South American and highland New Guinean tribes should also show signs of selection at the CLOCK locus, since they are even more prototypically "cad societies," and they have the highest frequencies of the 7R allele at DRD4. And 2) African Bushmen should show no signs of selection at CLOCK since they are more "dad societies" and have lower frequencies of the 7R allele at DRD4. (ALFRED does not have data on CLOCK.)

The fact that Northeast Asians do not show signs of selection at CLOCK already supports the hypothesis, since they are more "dad societies" and have a very low frequency of 7R at DRD4 (and even the 2R allele, which shows up somewhat there, has a much more muted effect than does 7R). The lack of selection at CLOCK in Central Europeans is neither here nor there: they are more "dad societies" than Western Africa but not so much as East Asia; Europeans also have intermediate frequencies of 7R and DRD4. So we could have an example of "Rushton's Rule," where East Asians show no selection for low-anxiety / high-novelty-seeking alleles at either DRD4 or CLOCK, Europeans show selection at just one locus, and West Africans show selection at both.

To the best of my knowledge, as they say, this is the first argument for why Africans show a signal of selection at CLOCK. Consider it part of the graduate student with a PC trend in studying human evolution. You heard it here first.


Chen, C., M. Burton, E. Greenberger, & J. Dmitrieva (1999). Population migration and the variation of Dopamine D4 receptor (DRD4) allele frequencies around the globe. Evolution and Human Behavior, 20(5): 309-324.

Harpending, H. & G. Cochran (2002). In our genes. PNAS, 99(1): 10-12.

Lynn, R., & T. Martin (1995). National differences for thirty-seven nations in extraversion, neuroticism, psychoticism and economic, demographic and other correlates. Personality and Individual Differences, 19(3): 403-406.

Roybal, K., D. Theobold, A. Graham, J.A. DiNieri, S.J. Russo, V. Krishnan, S. Chakravarty, J. Peevey, N. Oehrlein, S. Birnbaum, M.H. Vitaterna, P. Orsulak, J.S. Takahashi, E.J. Nestler, W.A. Carlezon, Jr., & C.A. McClung (2007). Mania-like behavior induced by disruption of CLOCK. PNAS, 104(15): 6406-11.

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Sunday, May 18, 2008

Male preferences and debunking myths about the evolution of the female form   posted by agnostic @ 5/18/2008 06:49:00 PM

Click for Uncensored
In the comments section to a 2blowhards post on booty shakin', blogger Alias Clio puts forth an argument from incredulity regarding several hypotheses I proposed: 1) that male preferences for different parts of the female body have, over time, correlated with personality traits; 2) that natural selection has had a role in causing some men to prefer one body part over another; and 3) that the correlation could be caused by some simple mechanism. She also repeats an evolutionary just-so story about why human females developed large breasts -- that is has something to do with face-to-face sex -- and that too is worth taking a hard look at (the story, that is).

As to 1), the available data do paint a somewhat clear picture that assmen, boobmen, and legmen are not the same on average for personality traits. What Clio doubts is that the correlations here and now can be projected back into the past or into other parts of the world. That's true enough, but it's true of anything psychological, and only for technical reasons: when we discover which gene variants in males are implicated in preferring T over A, we can dig up or unfreeze ancient humans, sequence their DNA, and see if the males were boobmen or assmen. That's how we found out that some Neanderthals were probably red-headed, despite the fossil evidence not telling us anything about their hair color.

Though everyone knows it's a dubious move, the best we can do to see what preferences may have been like in sub-Saharan Africa 100,000 years ago is to investigate present-day hunter-gatherers in Africa. The Hadza are a well studied hunter-gatherer group who live in Tanzania, and a study by Marlowe et al. (2005) (free PDF) shows that Hadza males prefer females who have a low waist-to-hip ratio in profile (i.e. due to protruding buttocks), rather than from the front (i.e. an hourglass or wasp-waist shape), while Western males prefer the converse. The authors did not collect personality data on the Hadza males, and did not test to see whether a male preferred boobs or buttocks, but in principle this would not be difficult to do, and we could see whether a similar pattern showed up among African hunter-gatherers.

That brings us to 2), whether or not natural selection had a role in the emergence of boobmen. Clearly they are a new morph within homo sapiens. They are too high in frequency to be the result of de novo mutations here and now, and they did not all migrate from some pre-historic Martian colony of homo sapiens. That leaves genetic drift or natural selection. Genetic drift can cause allele frequencies to go up or down over time, but it cannot produce design. Mate preferences are too specific and coordinated during development to admit a believable drift explanation: natural selection appears to have fashioned them.

But toward what end? We don't need to know, really. With the completion of the HapMap project, we are learning of tons of cases of natural selection in human beings, and we largely have no clue what it was up to. The numbers don't lie. Still, let's indulge in a little conjecture just to show that the idea isn't so perplexing in the case of boobmen.

In many areas of life, there is no one best solution, and we face a trade-off. If I develop conspicuous ornaments, that may make me more attractive to females, but it may also give me away to predators more easily, or provoke the envy of duller looking males, who might ostracize me (no small matter in a social species). Duller looking males might avoid predators and envy-based ostracism, and may be able to work better in groups because of this, but they won't be as attractive physically to females. The result is that some fraction of males will be dull and the rest conspicuous. We would need tools from game theory and differential equation modeling to spell out what parameters are involved, and what the exact frequency of each would be at equilibrium. But the point is that neither is universally favored, so both will co-exist.

So it could be with boobmen and assmen. I don't think these preferences per se were the target of selection, but again that they correlate with other personality traits that have been under selection. For instance, everyone says that compared to boobmen, assmen are more likely to have polygynous tendencies, to prefer short-term relationships, and to emphasize female qualities most relevant to the short-term (such as her most sexual body part, the derriere). We don't know if that's true, but it would be surprising if everyone had the same specific delusion. Since both short-term and long-term strategies have pros and cons, both could co-exist.

If being a boobman is linked to a more monogamous orientation, we are asking how natural selection could have driven up the frequency of monogamous males in societies where boobmen are common, such as Northern Europe. Maybe agriculture there requires the father to stick around and provide for his kids, whereas in parts of sub-Saharan Africa where farming has lower energy requirements, females can farm on their own and not worry about whether the father will stay with her. I don't claim that this is the only way it could have happened; this example is just to illustrate how simple the process can be.

Turning to 3), the mechanism does not have to be known in order to talk about the adaptive value of the trait (see Niko Tinbergen's Four Why's for clarification). We know that lighter eyes were selected for in Europeans, but we could know this fact even if we didn't know what biochemical pathways are involved in eye color. Still, let's indulge in a little more conjecture just to show how non-mysterious the mechanism can be. It may be as simple as testosterone level, with assmen having higher T than boobmen.

This is an incredibly easy hypothesis to study empirically, though from Googling it looks like no one has done so. To repeat a finding from the boobman, assman, and legman study, though, the assmen and those who prefer both large breasts and large buttocks have more ambitious personalities and are Type-A businessmen. We also know that in various species, such as the dark-eyed Junco, higher testosterone makes a male more polygynous and less likely to stick around to help raise the kids. Whatever the mechanism turns out to be, investigating the matter is not so perplexing that we don't even know where to start looking.

Last, let's examine some very popular but utterly ridiculous hypotheses for why human females evolved large breasts, summarized here. First of all, it is not true that human females have large breasts -- some have small, some medium, and some large. Look at the picture of the chimp in that summary -- you see human females with breasts that small (or large) all the time. This is not hairsplitting: it suggests that breast size reflects some trade-off.

For example, the trade-off could be in fat deposition: if you have a fixed amount of fat and want to be conspicuous, you had better put the bulk of it in one place or the other. Only gifted (or cursed) females have so much to go around that they can have large breasts and large asses. Those who put it in their chests are probably pursuing a long-term mating strategy, and those who put it in their behinds are probably pursuing a short-term strategy, on the assumption that female supply has evolved to meet male demand.

The evolution of breasts has nothing to do with mimicry of the buttocks -- can you think of any other way that a man might view buttocks-resembling things on a woman if he wanted to? Moreover, do assmen respond at all similarly to boobs as to the buttocks? This hypothesis predicts that they should be roughly interchangeable, but I don't even notice who has big or small boobs unless someone points it out to me, and I have no way of judging what "good boobs" look like, according to boobmen. It also has nothing to do with our species' face-to-face sexual position -- again, can you think of any other way a man might look at buttocks-resembling things while having sex? And as misleading as the name may be, doggy-style is not a trait that humans have lost, like a coat of body fur.

Neither does it have to do with our bipedal posture: it's true that this posture would have obscured any rump swellings (as chimps have), but the fleshy buttocks have still been in plain view ever since -- and typically, more viewable from afar than the breasts, as they take up more volume. Five-hundred years from now, the scientific consensus will be that invoking bipedal posture as a driver of some clearly unrelated change was the 20th century equivalent of ancient Greek theories about trepidation of the spheres.

Since such hypotheses are so easily debunked, why have they persisted for as long as they have? Napoleon said that you should never attribute to malice that which can be explained by incompetence, and here the incompetence surely stems from the majority of researchers and commentators in this area being boobmen, legmen, or women. (Women will grudgingly admit that boobs and legs can be things of beauty, but recoil in disgust upon pondering the booty.) We all have a tendency to extrapolate from the personal to the universal, but when I find out that someone thinks or behaves differently than I do, I ask what forces could cause them to think or behave in such deviant ways. That's how you get a clearer picture of how the world works, but it relies on there being a diversity of views within the field. It's about time some assmen joined the ranks of sex researchers to set the field straight.

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Monday, March 17, 2008

Traits of men who prefer breasts, booty, or legs   posted by agnostic @ 3/17/2008 08:11:00 PM

Pursuing a hunch inspired by a post on breast size and getting married by Irina, I managed to hunt down a study that shows the characteristics of the Boobman, Assman, and Legman. First though, I could not find any studies that investigated what non-obvious correlates there may be of breast size, rump size, or leg length. So I can't back up Irina's observation that larger breasts, as opposed to say a rounder butt, make a woman more likely to get married.

The idea is not ridiculous: females vary in their reproductive strategies, some specializing in shorter-term and some in longer-term relationships, for example. And like many strategic choices, there is likely a trade-off: to wit, between investing a finite amount of body fat more in the upper or more in the lower region. Larger breasts could reflect pleiotropic effects of genes that also contribute to being more focused on stability and the long-term in mate choice. Or perhaps men who are more of the "good dad" type have a bias toward larger breasts, so that these are a response to the preferences of guys who will stick around.

Moving on to what I do have data for, let's see what Wiggins et al. (1968) have to say about what men with different physical tastes are like. They asked 95 male college students which silhouette drawings they preferred, and these independently varied the size of the breasts, butt, and legs: each appeared in a "normal" size, somewhat large, large, somewhat small, and small. They completed personality questionnaires and provided demographic background info.

Men who preferred the "large" figure -- large breasts, large butt, and large legs -- were characterized by "a need for achievement." Those who preferred the "standard" figure -- normal size for all parts -- were characterized by "a tendency to be disorganized in personal habits." And as for the small figure -- small size for all parts --

Those who preferred the small figure tend to persevere in their work. They are not cynical about authority and reported coming from an upper-class background. Although the small figure was generally disliked by the present group of subjects (Table 1), it very well may be a preferred type among members of the upper class (Moore, Stunkard, & Srole, 1962) as suggested by the present data.

I don't think there's any deep evolutionary strategy going on with upper-class people preferring petite females. It could just be a fashion statement.

Men who like large breasts:

Also characterizing large-breast preference was a tendency to date frequently, to have masculine interests, and to read sports magazines. Further, large-breast preference was related to a need for heterosexual contact and for exhibitionism (saying witty things and being the center of attention). In social relations, men who preferred the large breasts tend to be non-nurturant and independent. This latter result gives support to Scodel's (1957) finding of a lack of fantasy dependence among college men who preferred large-breasted figures. In the present study, preference for large breasts was positively correlated with smoking and negatively correlated with endurance (perseverance in work habits).

Sounds like the Boobman is a gregarious "guy's guy."

Men who prefer boobs that are friendly and unpretentious:

Those who preferred small breasts tend to hold fundamentalist religious beliefs and to be mildly depressed. In contrast to those who preferred large breasts, those who preferred small breasts are nurturant in their relations with others. They are not cynical about authority and come from large, nonworking-class families. They are lacking in achievement motivation and are indefinite about career plans. As a group, they tend to be engineering rather than business majors.

Men who prefer large buttocks (that is, men who are not homosexuals):

Preference for the very large buttocks was characterized by a need for order (neatness, organization, orderliness). . . Those who preferred the largest buttocks figure tend to be business majors (accounting?) and tend not to be psychologically minded [* see note, agnostic]. In social situations, they are dependent and given to self-abasement (guilty, self-blaming). Their value orientation tends not to be stoic in nature.

Sounds like the Type A businessman or political leader. (I would say "alpha-male," but that wouldn't be very self-abasing, would it?) Quoth bodybuilder, badass actor, and governator of California Arnold Schwarzenegger (watch from 1:35 - 2:25 in this clip):

"I can absolutely understand why Brazil is devoted to my favorite body part - the ass."

Men who like small buttocks:

Unlike those who preferred large buttocks, those who preferred small buttocks tend not to be self-abasing. They tend to persevere in the completion of their work and do not feel the need to be the center of attention. As a group they tend not to be education majors and their reading interests do not include sports magazines.

Men who like large legs:

The most substantial correlate of large-leg preference is an abstinence from alcoholic beverages as indicated by the negative correlation with both drinking and amount of drinking. Those who preferred large legs are nonaggressive and self-abasing (guilty, self-blaming). They tend to be psychologically minded (intraceptive) and are characterized by a slow personal tempo. . . Subjects who preferred large legs indicated that they are not business majors and that they would choose their mother over their father if they had to make a choice. The personality pattern suggested by these correlates is one of inhibition and restraint in social situations.

Men who like small legs:

[P]reference for small legs is characterized by a strong need for social participation. Those who preferred small legs are characterized by needs for nurturance, affiliation, and exhibitionism. That is, they are helpful to others, feel a need for social participation, and like to be the center of attention in social situations. They are also socially dependent and tend not to stick at a task until completed.

So, men who like the "large" figure (the one who's tall and has t&a) are the more ambitious ones, the Boobman sounds like a social guy's guy, and the Assman sounds like a Type A businessman. It's possible to interpret this pattern as showing that the Boobman is more likely to settle down with one woman, while the Assman would be the polygynous executive type. Admittedly, the data aren't very clear; they certainly don't contain any direct information about willingness to marry, thoughts on monogamy, and so on.

It has been 40 years since this study was done, but in my search I could not find any follow-up studies -- you have to admit that it's not exactly a major research concern. If any readers know of similar studies, or especially of studies on the non-obvious correlates of female breast, butt, and leg size, please say so in the comments.

* I believe "not psychologically minded" in this case means they tend to think of people in simple stereotypes rather than using complex and varied concepts. Terms like "psychologically minded" and "intraceptive" are fossilized jargon from 40 years ago, and it's not totally clear what is meant.


Wiggins, J.S., J. Wiggins, & J.C. Conger (1968). Correlates of heterosexual somatic preference. J Pers Soc Psych, 10(1): 82-90.

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Sunday, February 24, 2008

Emotional fragility as a sexually selected trait   posted by agnostic @ 2/24/2008 03:02:00 PM

Roissy recently drew up a list of female skills for attracting males, and although it is clearly weighted toward succeeding in short-term relationships, the rank order seems about right for getting married too. One quick way to see what has mattered to men is to look for sexually dimorphic traits. As Darwin noted, such traits can have the flavor of "armaments," used to shove same-sex rivals out of the mating competition (such as deer antlers), or "ornaments" which attract mates (such as the peacock's tail), or both. I'll review some evidence that emotional vulnerability has been sexually selected in human females due to its attractiveness to males, rather than its use in female vs. female competition.

First, let's use YouTube to convince ourselves that emotional fragility makes a female more attractive, regardless of her physical appearance. Consider Emmylou Harris, Karen O, Elizabeth Fraser, or Hope Sandoval -- each is more desirable as a mate than if she were more tough-minded. In males, the attractiveness of fragility is conditional. If he can honestly signal manliness in dominating other males (however he does that), then emotional fragility around women may convince them that he's the best of both worlds. But if he lacks drive or ambition, then fragility will only make him appear needy and pathetic. Males who succeed here include Johnny Cash, Mike Ness, LL Cool J, and Joey Ramone.

Next, let me clarify the term "emotional fragility." It's a tendency to cry easily about something that would upset a caring person, a trait that will move men to protect and comfort her. More concretely, I'll treat it as a combination of the Big Five personality traits Neuroticism and Agreeableness, with more weight given to the former. A graph will help to illustrate [1]:

As for sex differences in these traits, see this previous post for a review of a meta-analysis by Costa et al. (2001). In brief, across all cultures of the world, females score higher than males on average for both Neuroticism and Agreeablness, though the magnitude depends on the physical and social environment that the population is adapted to: Europeans show huge sex differences, while Africans and East Asians show less pronounced differences. Among Europeans, the female mean is between 0.5 and 0.6 SD above the male mean for both Agreeableness and Neuroticism. A new cross-cultural survey by Schmitt et al. (2008) confirms this, although they find a slightly lower difference between means in Agreeableness. Both of these articles also provide good overviews of previous research.

While other personality traits show sex differences, Neuroticism and Agreeableness are by far the most dimorphic. Interestingly, in the first large-scale study designed to test changes in personality during adolescence, using a personality measure very comparable to an adult measure, McCrae et al. (2002) found a significant Time x Gender interaction effect for Neuroticism. During adolescence, females were much more likely to increase in Neuroticism than were males, in both the US and Belgium. Neuroticism declines for both sexes in the mid-20s, and drops even further by age 40. So, we observe a pattern of dimorphism that emerges just after puberty and gradually switches off beginning at the age when females would have had their first child. It is similar to physical attractiveness in females or muscularity in males, suggesting it has been sexually selected.

It is clear that fragility is unlikely to count as an "armament" used for same-sex competition, since it makes one more vulnerable to intimidation, teasing, and other forms of pushing one's same-sex rivals out of the mating market. We would expect it to be more of an "ornmament" that attracts mates, then. It may not make a female appear sexier, but when a girl starts to cry because she feels that she's become a burden to her friends and family, it may be nonsense, but a guy can't help but want to comfort her and protect her. Once she inevitably feels a little better, the guy will feel like he's performed his service as a man. And, modern malarkey aside, guys feel good when they do chivalrous and manly deeds, so that they would seek out women who offered the greatest opportunity to do so, and girls feel good when these acts are done for them. [2]

Moreover, comforting a female in need often involves close physical contact, such as holding her hand, holding her close and rubbing the upper part of her back, brushing the hair off of her face, or wiping the tears from her eyes. Physical bonding like this strengthens the relationship two people have, and also signals to her that the guy is a "protector of loved ones" (to borrow a phrase from the Mystery Method) -- a quality she is interested in during the years leading up to motherhood. It also tells her that he would take care of her if she became sick. So, it serves the dual purpose of attracting mates and detecting who among them is worth hanging onto.

[1] The fact that the Big Five uses the axes of low Neuroticism - high Neuroticism and low Agreeableness - high Agreeableness doesn't mean anything deep about how the traits are realized physiologically, or about how genes influence personality. We could rotate the old axes by, say, 45 degrees and come up a new set of two axes: a Tough-minded - Fragile dimension and a Cordial - Irascible dimension. The old traits of high A, low A, high N, and low N would lie in the quadrants of the new graph. In short, like a physicist, I'm perfectly free to chose my coordinate system to make life easy; I'm not claiming that things are different from how they're typically described.

[2] Of course, there is variation too -- some women succeed in the tough-minded niche and feel belittled when men try to do romantic things for them, and thus around whom men feel little motivation to behave in a chivalrous way. Roissy's many remarks about female lawyers serve as a good example of this.

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Sunday, February 17, 2008

Arms races and interracial encounters   posted by agnostic @ 2/17/2008 08:19:00 PM

After YouTubing VH1's The Pickup Artist (a contest reality show where guys learn how to pick up girls), something struck me about how the bar and nightclub scene so thoroughly devastated the East Asian contestant. Sure, every guy gets rejection anxiety and experiences rejection, including the occasional antarctic stare and turn-away response that the Asian guy received. But he looked like he was about to commit suicide, which he ended up doing symbolically by electing himself to be kicked off the show. You see the same stewing-in-rage pattern among Angry Asian Male websites, where they barely contain their bitterness about how White females show no interest in them. * Why is it that Asian guys seem to experience shell-shock in the bar and nightclub scene?

The answer may lie in the arms race between the sexes, whereby males become better and better at showing off or charming and seducing females, which makes females evolve higher standards for the showing-off trait or greater skepticism and iciness when they sense they're being hit on. It's clear that this arms race has escalated much farther in sub-Saharan Africa and other places of similar latitude, compared to more extreme latitudes (although latitude is not the primary cause -- probably pathogen load, ease of female farming, and so on, that correlate with it). So, when an Asian male is dropped into the lion's den of the Western bar and nightclub scene, he is not dealing with a merely unfamiliar group of females -- a large proportion of Europeans and Latin Americans -- but one that has evolved to defeat a far tougher opponent than he.

If European, Latin American, and African females have evolved levels of skepticism and strategies for rejecting an unwelcome suitor that reflect the levels of male seduction skill in their own populations, then when they use these against the far less threatening Asian male, he will perceive it not as a woman's natural self-defense, but as malicious overkill, as though a first-world superpower dropped bombs on a hunter-gatherer tribe that had picked off some of its members with crude arrows. **

Because there has been very little contact -- cultural or genetic -- between Europe, East Asia, sub-Saharan Africa, and the Americas for most of the time after these groups went their own way, it is not surprising that this pattern is pervasive when they meet for the first time. A well known example is the devastation of American groups when European colonists introduced pathogens that were not just unfamiliar but the outcome of thousands of years of arms-race evolution against the human immune system. Similarly, Europeans never managed to colonize sub-Saharan Africa: they dropped like flies in the even harsher pathogen-load areas there. There is no reason to expect the pattern would not show up in social arms races.

Steve Sailer has collected data on who marries who interracially: African male with White female is far more common than White male with African female. While plenty of causes have been given -- for example, dark skin is more attractive on males than on females -- I don't know of anyone mentioning the seduction arms race. African males would have an easier time charming over White females than African females, other things equal, since Whites are more naive to high-level seduction skills. *** Conversely, White males are underprepared in the charm department to evade the African female's more sensitive bullshit-detector, and their show-off skills are unlikely to meet her higher standards (in dancing ability, for example).

In general, it appears that females will date males of other groups if the latter are higher in seduction skills, and so males will date females of other groups if the latter are more naive to seduction than same-group females. I don't claim this accounts for all of the variation, since it would suggest East Asian female with African male would be the most common pattern -- but this datum is a thorn in the side of all other explanations too, such as differing levels of masculinity and femininity between groups.

* The rant linked to contains the following:

"I'd be willing to bet that you could scan entire racks of trashy romances at your local supermarket and not find a single one that depicts an Asian man seducing and romancing a white woman."

Well, the novelists have to keep the plot somewhat believable, and they have to supply a real rather than non-existent demand. The stereotype, probably true, is that East Asians are more pragmatic, tough-minded, and call-it-like-it-is compared to the more idealistic Europeans. But this example shows that the male contest for mates can fog up anyone's clear mind.

** Finnish males may also count here as honorary East Asians.

*** Maybe not so true for Italian females -- any female who's been to Rome or Staten Island knows how relentless Italian males are.

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Wednesday, January 16, 2008

Why do pretty girls look away when flirting?   posted by agnostic @ 1/16/2008 08:44:00 PM

Because they're not into you? Ha, no, I don't mean when they turn their head or whole body away. I mean when their body and head remain facing you but they move their eyes away, usually up and away but sometimes straight to the side. Imagine them giggling and saying "Wellll....." -- that look. (For those who need reminding: one example, another, and another, plus the Penelope Cruz picture in the link just below.)

To continue on a previous post that discussed a hypothesis for why humans have white eyes -- to help others detect what we're looking at, and thus thinking about? -- I suggest that this reflex of girls is an amplifier of an underlying index of phenotypic quality, namely large clear eyes.

The biologist Oren Hasson (free PDFs) has proposed a distinction between two types of animal signals: "indices" are honest indicators of underlying quality, while "amplifiers" make the index easier to perceive for the recipient. As an example, if others care about your ectoparasite load, then having plumage whose color was complementary to that of the bug would amplify your signal: even from a distance, it would be obvious who was clean and who was crawling with bugs. Your spot-free or diseased plumage is the index, while its bug-contrasting color is the amplifier.

(Say, that sounds like another reason why humans evolved lighter skin when they left Africa and adopted agriculture, which introduced a huge disease burden, especially diseases that produce and/or leave behind unpleasant, visible cues. It would be easier to spot who had "good genes" here if they had light skin. This cause is likely minor, but there could be something to it.)

In the case of girly girls, their large clear eyes are the index (this is something we pay attention to when judging the attractiveness of female faces), while the looking-away reflex is the amplifier. People with larger eyes show more white than do those with beady eyes. By looking away, nearly all of the visible eye is white, making it easier for onlookers to judge eye size. It is simply easier for us to judge the area of a solid figure (the nearly all-white eye) than the sum of the areas of scraps and bits (the white parts on either side of the iris when a person is looking straight at you).

And as always, this doesn't have to be the only reason that the behavior has evolved. One alternative is that it serves to playfully tease the male by denying him eye-contact. I find that unsatisfying (the hypothesis, not teasing), since there are many ways to break eye-contact, and the most common way to do so while flirting just happens to make it easier to see what large, dreamy eyes a person has.

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Sunday, November 25, 2007

Are tall women like Porsches?   posted by agnostic @ 11/25/2007 11:21:00 AM

We have already seen that female adult film stars are just average in height, while sexy celebrities are a half-sigma above-average. However, consider the heights of the 2007 Miss World contestants, whose median is 68.9 in (N = 106), a clearly significant difference from the US mean of 64.1 in. (where an SD = 3 in.), let alone the mean height of the second and third-world countries that most of the contestants come from. And though I can't find the original cite, many websites quote the Association of Modeling Agents as saying that female models should be at least 5'8. So, if tall women are not more attractive physically, as the first two data-sets suggest, but are more glamorous or prestigious, as the latter two suggest, there is a simple account of all of the data.

First, it's worth reviewing a few key facts about tall women and successful men, which come from Jensen & Sinha's (1993) excellent review of the physical correlates of intelligence. There is a positive correlation between height and IQ of roughly 0.2 -- however, all of this is due to between-family differences, as there is no within-family differences.

In other words, while members of tall families tend to be smart, within a given family, there is no relationship between height and IQ. Therefore, we can rule out some genetic causes such as pleiotropy, where a gene has effects on more than one trait; and genetic linkage, where genes for height may lie close to genes for IQ and be pulled along with them like teammates in a game of Red Rover. Common environmental causes like nutrition do not likely account for the pattern since most of the data comes from first-world populations not subject to much environmental stress, and also because the height-IQ correlation holds even among those with gifted IQs, who do no inhabit slums or want for basic nutrients.

Interestingly, the height-IQ correlation is entirely due to differences in leg length, since the correlation vanishes when sitting height is used instead of standing height. The simplest explanation that Jensen & Sinha propose is that there is cross-assortative mating between female leg length and male IQ. They summarize several studies which show that tall women, no matter what economic class they are born into, tend to climb the economic ladder more easily and marry higher-status husbands. That pools tall and smart genes into the same family, but any given kid of theirs doesn't get to pick and choose which parent he gets his height or IQ genes from, which explains why height and IQ are uncorrelated within families. Moreover, this is not a pattern only among the rich and bright: at every level of IQ, the pattern holds.

Jensen & Sinha suggest that men find tall women physically more attractive, and they mention the heights of Miss Universe contestants as support. But as we've seen, beauty pageant contestants and runway models are an entirely different group from adult film stars and sexy celebrities, who more accurately reflect what males find physically attractive. Therefore, to the extent that tall women are preferred as mates, it is probably so that the man can show her off as a hard-to-acquire status symbol, like a Porsche. This is an honest signal of high status since you don't have to conduct studies to know that a guy with a tall wife is far more likely to be a somebody than a nobody. That's especially true when the woman is not just tall, but taller than her mate, as shown in this gallery of famous shorter man / taller woman couples. We leave aside what makes a man high-status -- it could include wealth, power independent of wealth (as with Dennis Kucinich), and so on.

Broadcasting his status in this way might allow him to attract the attention of a large number of attractive onlooking females, who he may then seek on-the-sly copulations with. It may also allow him to be taken more seriously by his male colleagues and inferiors, and so to rise further in status: "Hey, that guy has a 6' tall wife -- he must be a real go-getter." Both of these effects serve to increase his reproductive fitness. And importantly, parading around your tall wife is a far less vulgar signal of status than, for example, driving up in an obscenely expensive car or sporting tons of jewelry. Consequently, the man does not suffer a loss of reputation as he would with those other signals, and because it is less conspicuous, he is less likely to draw the ire of those around him. He will provoke class envy in them, for sure, but he has to be careful not to enrage or offend them either, since social politics are central to his status.

Finally, because height is highly heritable, he may seek a taller wife more as a long-term wife than a short-term fling since he is concerned about the upward mobility of the children who he invests in. Mating with a tall woman will give his kids a leg up in the status competition. In the case of on-the-sly mating, he will not invest much in them later on, so he could be less worried about their social mobility -- just have a lot of them and hope some do well.


Jensen, A. & S. Sinha (1993). Physical correlates of human intelligence. In P. Vernon (Ed.), Biological approaches to the study of human intelligence, pp. 139-242.

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Heights of female adult film stars: Perfectly average   posted by agnostic @ 11/25/2007 12:04:00 AM

As a follow-up on a previous post about the heights of female sex symbols picked from the pool of celebrities, which found that they're about 1/2 SD above-average, let's now look at how tall adult film stars are. They're worth examining since they are chosen almost exclusively based on how attractive they are to the average male consumer, not how elegant or confident they appear. The website of the modeling agency that hosts the more elite stars -- LA Direct Models (NSFW) -- has height data for all but a couple of their members. If anything, these data are probably biased toward taller height since everyone lies in the upward direction.

Here is the frequency distribution of this sample of 121:

The mean is 64.5 in., the SD is 2.6 in., and the skewness is 0.24, which indicates it is weakly positively skewed (more of the points are bunch around the lower end). In a representative sample of the general population (see this PDF, p.10), females aged 20-29 have a mean height of 64.1 in. Because the adult film star sample could easily by biased by a half-inch, and because the means are close enough anyway, I won't bother running a t-test. If you really want to, feel free to post it in the comments, but it's clear that the adult film stars are not taller or shorter than the population at large.

Because the females are chosen only based on how physically attractive they are, this result goes against the hypothesis that long legs are in general physically attractive to men (although some men may find them sexy). There is another, non-physical reason why tall women may be preferred as mates, which I'll post about soon.

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Wednesday, September 12, 2007

Popularity of pretty boys and frequency dependence   posted by agnostic @ 9/12/2007 10:10:00 AM

In the comments on a previous post about height of pretty boys, Jason suggested that they're so popular because they appeal to younger girls who value not-so-threatening guys more than do older women, and because their non-threateningness appeals to a given woman throughout the majority of her menstrual cycle, unlike the virile caveman-looking guys who only appeal to her during the narrow window of peak fertility. I think this view confuses pretty boys with safe, gentle father figures, and so do most studies that forces females to choose between safe, non-threatening guys and macho men. That's because there are not just two ideal types of guy -- the tough, polygynous alpha male vs. the supportive, monogamous dad -- but three, including the polygynous pretty boy / rockstar type.

This is a well established typology elsewhere in nature: the Common Side-blotched Lizard shows exactly these three types. The "sneaker" Yellow males, from afar, look just like females, allowing them to fly under the radar and copulate with numerous members of an Orange alpha-male's harem. The monogamous Blue mate-guarders have only one female to watch, and they cooperate with each other due to green beard effects (free text of the published article), so they can defend their female against sneakers. The three morphs play out a frequency-dependent game of rock-paper-scissors that cycles every six years.

Right away, we've discovered one reason why so much genetic variation is maintained in traits relevant to sexual selection in humans, from personality traits to dancing ability to height -- there is likely no Evolutionarily Stable Strategy, since alpha-males can invade a population of demure good dads, fly-by-night types (pretty boys, artists, musicians, etc.) can invade an alpha-male population -- the latter might not worry about a pretty boy being around his girl since he might assume the guy was gay or otherwise unattractive to women -- but monogamous good dads can then clamp down on the fly-by-night debauchery by cooperating to erect morally upright social practices.

There's probably some difference in the ecology of humans and the lizards that accounts for why the frequency of human morphs don't follow a clean, periodic pattern. We probably face greater temporal and spatial heterogeneity, so that there's rarely a winner-take-all moment when one morph displaces just about all members of the prevoius morph. So it's not like rock-paper-scissors where each strategy totally defeats exactly one other, and is totally defeated by exactly one other (separate from who it beats). Also, human females likely have much more choice than the lizard females, and could follow a mixed strategy (i.e., choose different types of males).

Getting back to the datum that women find different types of guys more attractive when they're at their peak fertility during a menstrual cycle, we now see why pretty boys cluster more with alpha-males than good dads. Well, just behaviorally, babyfaced rockstars and actors are more likely to be polygynous than drab but devoted dads -- that's true for the lizards too.

It's an error to suggest that pretty boys have a non-threatening appeal: if that were true, then they would appeal more to older females, who are more concerned about security than cutting loose and throwing caution to the winds. Also, which cohort of females is most likely to date drug dealers, gang members, or other dangerous males? Or to commit crimes and act dangerously and barbarically themselves? Not the older ones. And it's pretty clear that females who dig Johnny Depp or Jared Leto are not thinking what a great father he'd make. Rockstars and dreamy actors have legions of eager groupies throwing themselves at them -- hardly a long-term strategy. That's true even with non-famous rockstars, although the groupies number fewer: think of how many talentless bums with guitars you've seen get the girls.

What is the more abstract trait that pretty boys and rockstars share with macho men, then? They're exciting, risky, volatile, and take-charge. So, the proper dichotomy is not "virile vs. wimpy" as has been supposed, but "exciting vs. drab," with the former having the two distinct sub-groups "macho man vs. pretty boy." Another way to see that this is the right dichotomy is to look around the world: wherever girls really dig macho men, they also dig the peacocky musician type too, finding safe guys a bit boring. And conversely, where devoted dads do the best, it's more difficult for macho men or in-town-for-a-day rockstars to make out like bandits.

Bobbi Low has shown that pathogen stress is positively correlated with polygyny (free PDF). So whatever it is about high-pathogen-load areas that selects for greater polygynous behavior -- maximizing your offspring's genetic diversity to stay ahead of the pathogens? -- will result in an increase in both gorilla-like and peacock-like males, since they're two viable ways to pursue a polygynous mating strategy. In particular, this resolves the paradox of why men of West African descent tend to show higher levels of both the belligerent tough-guy, as well as the high-pitched singer who can dance better than most girls and has a penchant for dapper dress. Scandinavia and Northeast Asia, by contrast, show lower levels of badasses and show-offs but higher levels of good dads. That follows from the pathogen-load hypothesis, combined with the three-part, as opposed to two-part, typology of ideal male types.

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Sunday, September 09, 2007

Facial attractiveness and correlation vs. experiment   posted by agnostic @ 9/09/2007 08:14:00 PM

The topic of facial attractiveness came up at Cognitive Daily, and it presents a good opportunity to contrast the two main approaches in psychology -- correlational and experimental. I'll start with an informal chat, and then proceed to look at a published study. Since the literature is vast, this will just touch on a few key points. And a warning to our mostly male readership: I'm only going to focus on what makes male faces attractive, both for "equal time" and because it's more mysterious.

Do girly eyes, lips, and skin make a guy less attractive? Hardly -- just look at any of those "teen hearthrob" magazines. In one response to a PNAS study, a photo of various dream guys features Billie Joe Armstrong next to the qualities "music" and "looks." What makes him look better than Bear Grylls and Kurt Vonnegut? Well, he has large girly lips and eyes, and tighter skin. This is typical of "pretty boys": other examples are Johnny Depp, Ryan Phillipe, and so on. However, the skeletal morphology (jaw, cheekbones, chin, brow) is masculine. It's only the non-boney parts that are girly.

So, for guys, we've already found two principal components of facial attractiveness: a manly skull and girly soft parts that fill it out. But this brings up a very important point in asking such questions. That is, cognitive scientists often hew to the experimental approach -- let's keep two faces exactly the same, but change one feature, and see which is more attractive. This game of Mr. Potato Head purportedly avoids the entangled mess of confounding factors that would turn up in a correlational study, such as one using principal components.

But there are good reasons to believe that there are non-trivial statistical interactions between facial features, so that isolating one and varying it misses the point: whether girly eyes are attractive depends on what the rest of the face looks like. It's just hard to judge the attractiveness of facial features out of context since facial perception is a pretty gestalt process.

It's clear that part of the variation in facial appearance is due to genetic differences between individuals. Whatever these variational genes may be, their effects are pretty fundamental. There are probably significant epistatic (or gene-gene interaction) effects in skull morphology just because so many different parts have to coordinate their work to make the face look right. (Here is a study showing epistatic effects on the symmetry of mice teeth.) Throughout development, a single gene could have pleiotropic effects on various parts of the face, and ditto for a single circulating hormone.

The point is, if we keep all of those the same and vary just one piece, we've lost the correlation structure. We could get wacko results for that reason alone. Imagine if a very ugly guy had his photo manipulated so that he had large girly eyes -- they would look very out of place, unsettling, perhaps jarring. We'd cringe from the bizarro effect alone. (For female faces, consider that very tight skin is attractive -- unless you take an old woman's head and give her a tight facelift, resulting in that extraterrestrial transvestite look.) In reality, though, girly eyes probably go along with other features that make them neutral or attractive.

With that in mind, let's turn to a study on girly facial features in guys. Here is a free PDF, so if you comment, at least look at the pictures and read the graphs. What the experiments show is that, keeping everything else the same, increasing the luminance contrast between the (darker) eyes and lips vs. the (lighter) rest of the face made a female face increasingly more attractive, but a male face increasingly less attractive. The interpretation is that female-typical traits are attractive in females but ugly in males.

If you look at the male pictures, though, it's clear why the feminized photo scored so low: he looks like a damned weirdo. Later in the paper, there are pictures of his entire head -- you can see that he has a very unattractive, schlubby male face. We react by cringing at his picture with high-contrast eyes and lips because it's so incongruous. Again, in real life, guys with more female-typical eyes and lips look like pretty boys, so it's not unsettling but rather attractive. I've already mentioned some mechanisitic reasons why that may be, but there could also be correlational selection on the skeletal and soft traits, or cross-assortative mating between males with manly skulls and females with doe eyes, pouty lips, and taut skin.

As a reality check on the unsexiness of high-contrast eyes and lips for male faces, in the picture of Billie Joe Armstrong that The Intersection chose to showcase his good looks, he is wearing heavy mascara -- just as Johnny Depp did for the Pirates of the Caribbean movies. I'll bet that's also part of the hunk appeal when attractive football or baseball players are photographed with that black stuff under their eyes (functionally unnecessary for having your picture taken).

Also, have a look at another study which created "average faces" from many real faces (these studies always show that the composite is most attractive). Their characteristics of beautiful faces shows a protypical sexy and ugly male face. First, note how similar the sexy non-skeletal features are for both sexes. It's hard to tell which face show a higher luminance contrast between the eyes and lips vs. rest of the face, since the sexy guy has darker skin. To me at least, the sexy guy has more pop-out-of-the-background eyes and lips, while the ugly guy has more uniformly drab features. But maybe a more sophisticated instrument than my eye will say that the sexy guy has lower-contrast features than the ugly guy. If so, the conclusion would be more believable since it did not come from a Mr. Potato Head experiment.

So, on a constructive note, the way these studies of facial attractiveness should be done is to do something like PCA on a huge dataset of certified dreamy and drab guys. Just "by inspection," it's clear that "manly skull" and "girly soft features (eyes, lips, skin)" are two. Symmetry is another one, although as I mentioned at Cognitive Daily, symmetry is not heritable, so don't think that says anything about "good genes" sexual selection using "fitness indicators."

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Sunday, July 15, 2007

Most phenotypic evolution is neutral   posted by agnostic @ 7/15/2007 05:22:00 PM

Still not convinced? See below the fold for some (tame but NSFW) evidence that phenotypic evolution tends not to have to do with survival and reproduction.

Data gathered from fieldwork in Brazil, Turkey, and Iran. Comparable data could not be found for blue-eyed, blonde-haired Finland. That probably doesn't mean anything either.


Friday, May 18, 2007

Dumb things guys do to impress girls   posted by agnostic @ 5/18/2007 01:19:00 PM

Retrospectacle gives the low-down on the Schmidt Sting Pain Index, which measures the pain of insect stings. The winner is the Bullet Ant that plays a central role in boy-to-man initiation rites of the Satere-Mawe tribe in Amazonia, as seen in this video. Returning to my post on daredevils, one episode of Jackass spin-off Wildboyz features Steve-O and Chris Pontius undergoing the ritual. See this video (some censored non-nudity). Their hysterics are somewhat affected, but no doubt it takes a bad MF to undergo this ritual multiple times for 10 minutes each time.

Why would a sane person do this? Easy: study the facial expressions of the local women after Steve-O and Chris undergo the ritual (about 2:15 in the video). Since facial expressions are pretty universal, we Westerners can recognize them as "my romantic curiosity has been piqued." And the girls are pretty, too -- now we understand why guys do stupid stuff like this. Not surprisingly, the creators of the two sting scales (Schmidt and Starr), are both male. I'm sure other obscure pain scales were developed by males as well, even if they're uncredited -- fraternity initiations must involve calculations of pain from similar sources. Scoville was male, but he measured spiciness according to what a panel of tasters thought.

This is yet another example of how culture could influence evolution: a ritual like the ant-gloves unmasks the ability to "take it like a man." Since the signal of manliness is amplified by extraordinary circumstances like these, the females now don't have such a hard time teasing it out from the noise of quotidian goings-on and can thus make better decisions about who to mate with. Branding and tattoo-ing likely serve similar functions, aside from whatever other roles they may play.

On a personal note, I'm not a paragon of machismo, but I figured out early on that I have a very high tolerance for needle pain. At 22 I decided to have my forearms tattooed (tastefully), and I'm surprised by how intrigued girls have been by them. They often fondle your arms as they inspect them -- not the worst thing in the world. A co-blogger has also noted that girls dig non-tasters, i.e. someone who can eat fire without flinching (though in his case the attention is unwanted, as he has a girlfriend). Males have duller palates (see here too), making non-tasting a more masculine trait. That could be why men with overly refined palates are perceived as effeminate. In any case, here too culture could unmask who is manly vs wimpy.

True, not all cultural / technological advances will allow previously unnoticed males to become manly men -- World of Warcraft addicts will always be dateless -- but that still allows for adaptive radiation into many other "now open for business" niches. There is also the not mutually exclusive possibility that selection is acting on other, correlated traits (e.g., for certain personality types).

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Monday, April 16, 2007

Heights of daredevils: shorties get the girls   posted by agnostic @ 4/16/2007 08:46:00 PM

To expand on the findings of a previous post on shorter guys dominating the pretty boy and hip hop niches, itself inspired by a discussion at Steve Sailer's blog on short guys dominating the rockstar niche, let's now consider the average height of males who specialize in another show-off niche: daredevils. Since performing physically dangerous stunts must require a certain degree of athleticism, you might think that daredevils would tend to be taller than average, as in basketball, football, and other popular sports. On the other hand, perhaps what counts more than height or dominance are nimbleness, ability to maintain one's balance, and being a smaller target (e.g., when being charged by a bull or having darts thrown at one's body). To investigate, let's have a look at the heights of the main cast of the popular MTV daredevil show Jackass. [1] Examining just the hardcore, professional members:

Jason Acuña - 4'7
Bam Margera - 5'8
Chris Pontius - 5'8
Preston Lacy - 5'8
Ryan Dunn - 5'9
Brandon Dicamillo - 5'9
Steve-O - 5'10
Dave England - 5'10
Johnny Knoxville - 6'0.5
Ehren McGhehey - 6'1

Using the data at the excellent celebheights.com website, I could only verify the heights of Knoxville, Margera, and Steve-O (in the thread on Knoxville). The other heights are from their imdb.com entries, and so are probably exaggerated by 1 inch or so (this is clear from comparing cast members when they stand side-by-side in stunts). Making no adjustments, and leaving aside the outlier of Jason "Wee Man" Acuña (a "little person"), the mean here is 5'9.7; while reducing the unverifiable heights each by 1 inch gives a mean of 5'9.1. For American males age 20-39 (see the PDF here, p.10), mean height is 5'9.6, based on a sample of 1441. I assume the SD for height of the general population is 3 in., though the test is not affected by any reasonable choice. We accept the null hypothesis of no difference in means between daredevils and a random sample of males, regardless of whether we use the unadjusted or adjusted data (both p greater than 0.6 using a two-tailed t-test). Even norming to non-Hispanic White height does not make the results significant (p ~ 0.3). Admittedly the n is small, and perhaps a larger dataset on professional daredevils would resolve the issue of whether there truly is no difference or whether the non-significant trend toward shorter stature here is actually significant.

Looking at a related group of elite athletes in "extreme sports" such as skateboarding and BMX (rather than the all-purpose daredevils of Jackass), I found this handy webpage for a star-studded event that includes height info. NB: Tony Hawk is actually ~6'2, not 6'3 as reported at the above website (let alone the claim of 6'4 at imdb.com), according to several profiles (e.g., this one and this one), and by comparing him and Johnny Knoxville when they stand side-by-side in a stunt for Jackass Number Two. It's always safer to round down when we're talking about self-reported male height. Comparing the mean of these 15 males -- 5'9.3 -- with that of the aforementioned representative sample of American males, we again accept the null hypothesis of no difference in means (p greater than 0.7 using a two-tailed t-test). As with the stunts of "well-rounded" daredevils, those of the specialists too do not appear to demand taller or shorter than average height.

So, if daredevils tend to be of average height, why the insinuation in the title of the post that they qualify as "shorties?" In the mating arena, the minimum height for an American male to qualify as a "good blind date" is probably 6' or 6'1, so that men who are shorter than this must make up for it somehow. For example, a study of online dating outcomes (PDF) suggested that a 5'10 male would have to earn $32,000 more than a man of 6' in order to receive the same amount of attention from women. The idea is that females are more concerned with quality than quantity of mates, so that they focus on traits as proxies for quality. Since it's rare to find a male who scores highly on all desirable traits, most women face a trade-off between competing "almost dream guys."

Being a professional daredevil is a pretty easy way to signal your genetic quality -- only the truly blessed can perform one dangerous stunt after another without being disfigured, mamed, paralyzed, or killed (watch the bloopers reel for amateur daredevils and see). You need at least general intelligence, boldness and risk-taking, and physical deftness / coordination. So, this could be another instance of the Handicap Principle. Once the first few daredevils in history figured out that they could impress girls as sex symbols, they would have had more children than the population average, increasing the frequency of alleles implicated in the relevant traits. This logistic growth would have continued until their niche became saturated (i.e., when it would pay off more to specialize in some other niche than join the daredevils). Again, it's hard to attention-whore when everyone is exhibitionistic in the same way. [2] This show-off quality is what distinguishes the daredevil niche from others that might also preserve variation in daredevil-ish traits, such as that of young soldiers (cannon fodder). By hypothesis, daredevils are more narcissistic than soldiers.

These processes will maintain genetic variation in traits such as excitement-seeking and height when other pressures might want to erode such variation; e.g., females might in general want a 6' partner or a cautious father of her children. In the comments of a related post on the heights of female sex symbols, Jason asked whether the trend toward shorter male height was an effect of production companies wanting to minimize the height difference between male and female stars, preventing awkward shots. The data on daredevils suggests that this is not a reason, as they rarely appear kissing females on film, and the same is true of rockstars.

And returning to another post on the role of technology in preserving variation, new technology will help people to identify who is cut out to be a daredevil since most stunts involve taking punishment from some product of human artifice, taunting but escaping from a deadly predator using technology, and in general using technology to push the limits of human performance. Now, this is not to say that pre-industrial individuals were jumping off cliffs with a parachute, but the Spanish matador requires only a sword (and really a stick with a large, sharp arrowhead might do). Also, Jackass members Chris Pontius and Steve-O developed their own daredevil show, Wildboyz, in which they often don't use technology at all, but rely on withstanding assults from wild animals (e.g., having their buttocks stung repeatedly by scorpions or surviving a swim with killer sharks). So, there's no reason this dynamic could not have started tens of thousands of years ago, although surely recent history, during which human beings have radiated into a myriad of diverse physical and social environments, will have created different frequencies of such traits between populations. [3]

We now turn to the question of whether daredevils actually do manage to mate with top-choice females, since status per se isn't attractive (as Half-Sigma likes to point out w.r.t. World of Warcraft nerds). Here are some photos of the girlfriends / wives of the sub-6' daredevils:

Bam Margera's wife
Bam Margera's former fiance
Chris Pontius' wife
One of Steve-O's girlfriends (others)
Best example: Wee Man's girlfriend (see pics "w/ Trisha")
Dave England's wife
Dave Mirra's wife (in the middle)
Carey Hart's wife is singer Pink
Bucky Lasek's wife

Perhaps more important than quality is quantity of mates, since the latter is more of a limiting factor on male reproductive success. Steve-O says here that he often sleeps with groupies, and judging from the friends on the MySpace pages of the Jackass members, their groupies are plenty -- and plenty attractive. On a final note, the shorter male readers should take this into account when encouraging your sons to take up one activity or another: if you want them to be successful with females, they'd better train hard to enter a niche that's tailored to short or average-height guys.

[1] No student of human biodiversity can forever avoid pop culture icons, filled as their ranks are with freaks and deviants of all kinds. The only DVD I've ever bought is Jackass Number Two, which I highly recommend to all the young male readers, if you haven't seen it already. The DVD contains lots of bonus footage, too. It is easily one of the most hilarious movies I've ever seen. For those who are unfamiliar with the material, here are a few illustrative examples from YouTube (both NSFW): here and here.

[2] Another clear example of the exhibitionistic appeal of the Jackass members is that they frequently engage in very homoerotic behavior, although none are gay. This is like the increasingly large group of straight girls in college (and, I hate to think, high school) who conspicuously make out with each other at parties (leks) in order to monopolize the attention of the alpha males.

[3] One puzzle is why sub-Saharan Africans are not only underrepresented among daredevils, but are positively freaked out as a group by the idea. (Watch any black stand-up comic show long enough, and soon you'll learn that they love to joke about how insanely death-defying White people can be, in contrast to the sensible Blacks. Another frequent topic is that White people stick around to find out what's going on in a calamitous situation, whereas Blacks immediately get the hell out of there.) This is a puzzle because they are well represented in most other show-off niches such as dancers, singers, athletes, models, and so on. Two possible reasons for this are the aforementioned aversion to "danger in nature," as well as their group's mean IQ of 85. Again, part of the daredevil appeal is that you rely on smarts to avoid accidents. Linda Gottfredson recently argued that avoidance of accidents was part of the reason why human beings became more intelligent (her first paper under 2007). The Jackass members are smart enough to pass high school-level classes at least (though Chris Pontius dropped out); Steve-O attended the University of Miami for a time, and his father is a high-ranking business executive.

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Sunday, April 15, 2007

Female sex symbols: somewhat taller than average   posted by agnostic @ 4/15/2007 05:48:00 PM

A recent John Tierney blog entry cited a much discussed study of online dating behavior (PDF), which suggests that shorter than average women have it easier in the online dating market, with the ideal height being about 5'2 - 5'3, and taller heights incurring increasingly greater costs. [1] However, women clearly vary in height well outside this range, so something is responsible for so much variation in height being maintained. Here I examine a fairly obvious, partial reason: being somewhat taller than average pays off if a woman is specializing in a niche that depends on sex appeal, in particular sex appeal that incorporates a fair amount of moxie / aggressiveness.

To test this hypothesis, I used celebheights.com to determine the heights of the women listed in the Maxim 2006 Hot 100 ranking. It's somewhat of a "sample of convenience," but it's hard to argue that the women there aren't sex symbols or that Maxim has an irrational bias toward women of a certain height. I could only find data for 77 of them [2], which you can see below the fold. [3]

The above frequency distribution by two-inch blocks (up to and including the right endpoint) shows that the heights of sex symbols are approximately normal (skewness = 0.07, or essentially symmetrical), with mean = 65.6 in. and SD = 2.8 in. A representative sample (PDF p.10) of 1,371 US women aged 20-39 showed that their mean height is 64.1 in., making sex symbols on average 1.5 in. taller than the average American woman. Using any reasonable estimate of variance in the general female population, a two-tailed t test shows that this difference in means is significant (t = 4.5, p less than .0001 -- perhaps lower; my calculator cut it off there). Clearly, being a bit taller than average helps in becoming a sex symbol. But does it matter even within the sex symbol set? Not really. Here is rank in the list as a function of height:

The Spearman rank correlation coefficient between height and rank in the list is 0.14 but is not significant (p greater than 0.2). So, being a bit taller than average probably helps you get noticed, but it is not of central importance. Note, though, that the non-significant relationship is not due simply to a restricted range for height in this sample -- the SD of 2.8 in. is close enough to the commonly used estimate of 3 in. for the general population.

Having established the greater average height of such women, what accounts for this pattern? This tends to be the most bullshitty part of a report, so I'll just throw out some guesses, and readers can add their own two cents in the comments. (Apologies for not researching / citing this section, but my hunch is that it'd be easy to dig up a few references for and against each of the guesses, as the "why" is always harder to pin down.)

Conjectures that assume there's something sexy about tallness per se:

- Longer legs. My eyes feast upon other parts, so perhaps in the comments the leg men can explain the appeal of long legs.

- Greater height tricks the eye into seeing a thinner figure. Fatter is usually not sexier (unless it's fatter than Kate Moss), since it reflects poorer health.

Conjectures that assume height isn't sexy per se, but that it covaries with some sexy other traits:

- Greater height could reflect a higher degree of male-typical hormones, which would aid the female in projecting the less passive / "take what she wants" attitude that characterizes sex symbols.

- Greater height could reflect better nutrition and healthy development in general -- think of all those Midwestern model types who grew up away from pathogen- and- toxin-infested urban areas. Good health is sexy per se.

A conjecture that assumes height isn't related to sexiness at all:

- Greater height is necessary to stand out from the crowd and intimidate other women in the entertainment industry. Maybe the average guy couldn't care less about a woman's height, but to break through and survive in a cut-throat industry, sheer height helps.

Whatever the reasons turn out to be, it's clear that there are reproductively prosperous niches that taller than average women are suited to, so that some genetic variation in height will be preserved despite males' apparent greater interest in females who are 5'2 - 5'3. Presumably the same is true in the other direction: former rockstar Shakira says here that being petite (she is ~5'1) causes men to act protective around her. Petite women might have a more sprightly, giggly appeal; so, alleles for shorter height could be preserved either due to the sexiness of girly girls or due to their receiving more protection and investment from others because of their pedomorphic stature.

[1] Oddly, the authors phrase this as a trade-off of height vs. income -- i.e., how much more income would a 5'10 woman have to earn compared to a 5'4 woman in order to garner the same amount of male attention? This makes sense when looking at female preferences since most female online daters are concerned principally with the guy's height and income, and thus face a trade-off should a particular guy not excel at both traits. It makes zero sense to look at male preferences this way, though, since most men are interested in many other physical traits before height even enters their mind, and income and power are not sexy to most men.

[2] I coded the women by rank only, so if a reader wants to know which data are missing, I'll upload the Excel sheet, and they can see for themselves. Almost all of the missing data are from the bottom of the ranking anyway, so the more important points are accounted for.

[3] I took the cited height for granted if it was an integer; otherwise I browsed through the text of the entry and discussion to decide which number was most accurate, sometimes rounding up, sometimes down, and sometimes keeping it as is. (19 of 77 data-points are non-integers, so I didn't round indiscriminately.)

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Tuesday, April 03, 2007

Cultural evolution causes biological evolution   posted by agnostic @ 4/03/2007 07:13:00 PM

Returning to a favorite theme here -- debunking the balderdash that recent human evolution is cultural rather than biological -- consider how simple technological changes can influence human biological evolution. Take musical instruments: in an environment with no musical instruments, and thus essentially no music, you'd never know who were the rockstars (if male) or the dancing queens (if female). With no way to detect these sexy phenotypes, natural selection could not change the frequencies of alleles that contributed to them. But once the presence of musical instruments becomes a predictable feature of the environment, suddenly there's a pressure to be a good performer, and so traits both physical (dexterity, agility) and psychological (extraversion, emotional volatility) will increase, at least up to a point where any further increase would be a bad bet for newcomers as they crowd an already saturated niche. It's hard to show off when everyone else shows off in the same way.

Now, we commonly urge youngsters to "find their niche," yet many people ignore the obvious corollary of this ecological phrase, namely that whatever cultural processes spawn new niches will also result in a change in frequency of alleles implicated in the traits needed to thrive therein. Unlike Darwin's finches, humans don't need to expand into an unsettled archipelago to undergo adaptive radiation -- we can stay fixed geographically but broaden the range of niches in our "social-cultural space."

At my personal blog, I sketched out a reason for why technological progress tends to be more bustling than progress in more abstract disciplines like geometry, where progress appears to stagnate for quite awhile until "the next big thing" comes along. Basically, the purer arts and sciences are the hobbies of weirdos, whereas technology is usually a matter of life and death: i.e., outperforming the technology of your adversaries. This literal arms race keeps the pace of technological progress much more frenzied than in other cultural areas. The key is that new shields, spears, guns, and ships don't affect the fitness of just soldiers, because most of this new stuff will be ripped off by others to innovate civilian life.

For instance, there would be no common cars if militaries had not pioneered the technology of interchangeable parts and mass assembly-line production for ships and firearms. Nor could their interiors and exteriors be held together were it not for the common use of steel, an alloy whose first modern production method -- the Bessemer Process -- resulted from its inventor's efforts to more efficiently produce firearms for the Crimean War, and whose Captain of Industry (Andrew Carnegie) made his fortune through contracts to build warships for the US Navy. And since the widespread availability of the automobile, many males have carved out a niche whose appeal to females centers around owning a car when other males don't (the guy in 10th grade with his own car) or using their car to signal machismo (drag racers). So, to paraphrase a related slogan on technological changes fueling biological changes: howitzers hatched heart-throbs in hot rods.

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Thursday, January 25, 2007

Blondes are not sexier: What the theory predicts and the data say   posted by agnostic @ 1/25/2007 11:42:00 PM

Steve has an interesting post on assortative mating in which he purports, in passing, that blondes have greater sex appeal, citing Peter Frost's hypothesis that blonde hair was sexually selected in Northern Europeans (I'll post on the assortative theme later). A danger in discussing which traits might be sexually selected is that the ponderer will likely go with what they personally find sexy and ask why such things might be sexually selected, rather than work from an independent angle. For example, I am very picky about the upper eyelids -- if they have that half-moon shape, that really does it for me. I've heard Michael say once that he likes this feature too -- but then, we're probably weirdos, or at least that's the conclusion until someone can show that a large fraction of guys prefer this feature, and that there's good reason to think it was sexually selected. Unlike half-moon eyes, blonde hair color receives lots of attention as a potentially sexually selected trait, but is a key prediction met -- are blondes sexier?

Below the fold, I briefly review some theory but mostly present data from all winners in three beauty contests, which indicate no overrepresentation of blondes. I conclude that hair color is of weak importance at best in accounting for sexiness, that the role of sexual selection in accounting for hair color variation is also weak at best, and that the perception that men are more likely to find blondes sexy is due to a passing fad for blondes during the decade from the mid-1970s to the mid-1980s.

First, Steve notes:
One of the most common storylines in movies is this: the blonde debutante gets engaged to the blonde fraternity president, but then she falls hard for the tall, dark, and handsome boy from the wrong side of the tracks.

The idea again is that blonde hair is sexy in females, not males. But just as common as the above scenario is the guy whose feelings for his fair-haired maiden waver once he becomes enchanted by a woman with coal eyes and raven tresses. For instance, in The Hunchback of Notre Dame (see here starting at line 57), the once pure priest Frollo describes how, after watching the gypsy Esmeralda dance and sing, he became so bewitched that he could not stem the tide of lust rising within him and fell madly in love with her. Shakespeare's "Sonnet 147" expresses a similar predicament: the speaker's got it bad for a bad girl! Not the first, nor the last. Interesting though literature and film may be, let's get to the theory and data.

Starting with the predictions from theory, the hypothesis that icy climes select for greater sex appeal is probably wrong. Gangestad & Buss (1993) showed that people in more pathogen-wracked areas emphasize "good looks" more strongly, and these are generally not icy areas. Think about the rest of the animal kingdom: where are the sexy, showy specimens with the most ornate song patterns? Same answer: mostly pathogen-infested areas, the tropics, etc. Consider the quintessential animal with exaggerated sexually selected traits -- the peacock -- whose rarer variant is native to Southeast Asia, and whose more common variant is native to the world's germ-cauldron (South Asia). Hamilton & Zuk's (1982) explanation was that these traits signaled better health to mates, no small feat in such areas. So, the prediction is that sexual selection will be very weak in Northern Europe (defined as the non-Mediterranean countries), where blondeness reaches substantial frequencies.

But even if sexual selection were a strong pressure there, what independently motivated evidence is there that blondeness is sexy, so that males who are sexually selecting would choose it over brunette hair? Again, the only good guess people have made is that sexually selected traits signal lack of being parasitized. For hair, though, this has mostly to do with the texture, lustruousness, and so on, not color -- although I'm willing to be corrected if someone knows of studies showing that blonde hair is more likely than dark hair to thwart the entry of pathogens into the scalp area. In any event, the main problem remains: in general, pathogen pressure is relatively very low in areas where blondeness is prevalent.

Turning now to the data, I recently posted about the list of who Maxim magazine ranked the hottest women for 2006, and there was no evidence of overrepresentation of blondes. The same is true for the other "lad mags" that you see in drug stores. Now I look at two other datasets that are probably more informative than who Maxim thought was hot in 2006: the winners of the Miss Universe and Miss USA beauty pageants. (The Miss America competition is not primarily a beauty pageant, as looks account for just 35% of the score). Such lists are preferable for testing the "sexy blonde" hypothesis since the individuals represent a very elite level of eminence. I looked up galleries of the winners, and if a girl's hair color wasn't clear from that, I did a Google image search for her. I judged overrepresentation based on the frequency of light hair according to Peter Frost's map at the Wikipedia entry for hair color.

For Miss Universe (gallery), there are 56 data points: 12 (21.4%) have light hair, 43 (76.8%) have dark hair, and 1 (1.8%) is pretty in-between. Now, 21.4% is surely a greater fraction of blondes than there are worldwide, but remember that Miss Universe doesn't represent the entire world -- it's mostly Europe and its offshoots, plus the white and mestizo populations of Latin America, and a tiny handful of East Asian countries (not China). For the non-Mediterranean areas of Europe, 21.4% is on the low-end of normal, but on the high end of normal for the Mediterranean (and so, for the mostly Mediterranean-looking Latin Americans who compete). I interpret this as supporting the null hypothesis of no effect of hair color on sexiness.

As for Miss USA (gallery), there are 60 data points: 17 (28.3%) have light hair, 38 (63.3%) have dark hair, and 5 (8.4%) have borderline hair. Although the fraction is larger here, remember the US is much blonder than the Mediterranean and Latin American countries who are also big contenders in the Miss Universe competition. Because the vast majority of the US population has been Northern European since the pageant began in 1952, we should determine overrepresentation based on the Northern European areas of Peter Frost's map. Doing so, we see that 28.3% is easily at expectation, and if anything is a bit on the low-end of normal for a predominantly Northern European population. Again, this result supports the null hypothesis.

In sum, we note that when put to a stringent test, blondes appear no sexier or uglier when compared to brunettes. Datasets such as Miss Universe and Miss USA are particularly instructive since the bar is set rather high. Then whence the perception that men find blondes sexier? There is an interesting temporal wrinkle in the data -- blonde winners are not evenly distributed in either dataset. For Miss Universe, from 1952 - 1974, 17.4% of the 23 winners are blonde; from 1975 - 1984, 60% of the 10 winners are blonde; and from 1985 - Present, either 8.7% or 13.0% of the 23 winners are blonde (depending on whether you are generous and code the 1 borderline girl as blonde). There thus appears to be a general lack of interest in blondes (and if anything, a dispreference for them), punctuated by a decade where blondes were very fashionable. Does the same pattern show up in the Miss USA dataset? Pretty much. From 1952 - 1973, 25% of the 24 winners were blonde; from 1974 - 1986, 50% of the 14 winners were blonde; and from 1986 - Present, 18.2% of the 22 winners were blonde. We note again the spike in blonde fashionableness from the mid-1970s to the mid-1980s.

I suggest that those who came of age during this Blonde Decade -- those who were born between roughly 1955 and 1970 -- may have unwittingly projected their perception of the sexiness of blondes onto time periods for which the view is not true. Combine this with the theoretical problems noted earlier, and it seems likely that sexual selection's role in increasing the frequency of blondeness is weak at best. That still doesn't answer the question of why blondeness evolved -- though I'll leave that for another post (or someone else can take it up). The explanation that I (and others) find most convincing for now is based on Jerome Kagan's work, starting in the mid-1980s, which has showed that light irises correlate with behavioral inhibition, suggesting that in Northern Europeans there was selection for different values of certain personality traits, which happened to also affect their eye & hair color.

Appendix: Hair color data for Miss Universe and Miss USA winners

Miss Universe (L = light, D = dark, M = borderline)

L 1952-Armi Helena Kuusela Kovo-Finland
D 1953-Christiane Magnani (Martel)-France
D 1954-Miriam Jacqueline Stevenson-USA
L 1955-Hillevi Rombin-Sweden
D 1956-Carol Laverne Morris-USA
D 1957-Gladys Zender Urbina-Peru
D 1958-Luz Marina Zuluaga-Colombia
D 1959-Akiko Kojima-Japan
D 1960-Linda Jeanne Bement-USA
L 1961-Marlene Schmidt-Germany
D 1962-Norma Beatriz Nolan-Argentina
D 1963-Ieda Maria Britto Vargas-Brazil
D 1964-Kiriaki “Corinna” Tsopei-Greece
D 1965-Apasra Hongsakula-Thailand
L 1966-Margareta Arb Arvidsson-Sweden
D 1967-Sylvia Louise Hitchcock-USA
D 1968-Martha Maria Cordeiro Vasconcellos-Brazil
D 1969-Gloria Maria Diaz Aspillera-Philippines
D 1970-Marisol Malaret Contreras-Puerto Rico
D 1971-Georgina Rizk-Lebanon
D 1972-Kerry Anne Wells-Australia
D 1973-Maria Margareta Moran Roxas-Philippines
D 1974-Amparo Muñoz Quesada-Spain
L 1975-Anne Marie Pohtamo-Finland
D 1976-Rina Messinger-Israel
D 1977-Janelle “Penny” Commissiong-Trinidad/Tobago
L 1978-Margaret Gardiner-South Africa
D 1979-Maritza Sayalero Fernández-Venezuela
L 1980-Shawn Nichols Weatherly-USA
L 1981-Irene Lailin Sáez Conde-Venezuela
D 1982-Karen Dianne Baldwin-Canada
L 1983-Lorraine Elizabeth Downes-New Zealand
L 1984-Yvonne Ryding-Sweden
D 1985-Deborah Carthy-Deu-Puerto Rico
D 1986-Bárbara Palacios Teyde-Venezuela
D 1987-Cecilia Carolina Bolocco Fonck-Chile
D 1988-Porntip Nakhirunkanok-Thailand
L 1989-Angela Visser-Holland
D 1990-Mona Grudt-Norway
D 1991-María Guadalupe “Lupita” Jones Garay-Mexico
D 1992-Michelle McLean-Namibia
D 1993-Dayanara Torres Delgado-Puerto Rico
D 1994-Sushmita Sen-India
D 1995-Chelsi Pearl Smith-USA
M 1996-Yoseph Alicia Machado Fajardo-Venezuela
D 1997-Brook Antoinette Mahealani Lee-USA
D 1998-Wendy Rachelle Fitzwilliam-Trinidad/Tobago
D 1999-Mpule Keneilwe Kwelagobe-Botswana
D 2000-Lara Dutta-India
D 2001-Denise Marie Quiñones August-Puerto Rico
D 2002-Oksana Fyodorova (Oxana Fedorova)-Russia (dethroned)
D ---Justine Lissette Pasek Patiño-Panama
D 2003: Amelia Vega Polanco-Dominican Republic
L 2004: Jennifer Hawkins-Australia
D 2005: Natalie Glebova-Canada
D 2006: Zuleyka Jerris Rivera Mendoza-Puerto Rico

Miss USA

D Jackie Loughery 1952
D Myrna Hansen 1953
D Miriam Stevenson 1954
L Carlene King Johnson 1955
D Carol Morris 1956
D Leona Cage 1957
L Charlotte Sheffield 1957
M Eurlyne Howell 1958
D Terry Lynn Huntingdon 1959
D Linda Bement 1960
D Sharon Brown 1961
D Macel Wilson 1962
L Marite Ozers 1963
L Bobbie Johnson 1964
L Sue Downey 1965
D Maria Remenyi 1966
D Sylvia Hitchcock 1967
D Cheryl Ann Patton 1967
D Dorothy Anstett 1968
L Wendy Dascomb 1969
D Debbie Shelton 1970
D Michele McDonald 1971
M Tanya Wilson 1972
D Amanda Jones 1973
L Karen Morrison 1974
D Summer Bartholomew 1975
D Barbara Peterson 1976
L Kimberly Tomes 1977
L Judi Andersen 1978
M Mary Therese Friel 1979
L Shawn Weatherly 1980
L Jineane Ford 1980
L Kim Seelbrede 1981
D Terri Utley 1982
D Julie Hayek 1983
D Mai Shanley 1984
D Laura Martinez-Herring 1985
L Christy Fichtner 1986
D Michelle Royer 1987
D Courtney Gibbs 1988
D Gretchen Polhemus 1989
D Carole Gist 1990
M Kelli McCarty 1991
L Shannon Marketic 1992
D Kenya Moore 1993
D Lu Parker 1994
D Chelsi Smith 1995
D Shanna Lynn Moakler 1995
D Ali Landry 1996
D Brook Lee 1997
D Brandi Sherwood 1997
M Shawnae Jebbia 1998
D Kimberly Ann Pressler 1999
D Lynnette Cole 2000
L Kandace Krueger 2001
D Shauntay Hinton 2002
D Susie Castillo 2003
L Shandi Finnessey 2004
D Chelsea Cooley 2005
L Tara Elizabeth Conner 2006

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