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The Science of Gaydar

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EXAMPLE B: Thumbprint Density (Male)
Gay men and straight women have an increased density of fingerprint ridges on the thumb and pinkie of the left hand.  

As he recruited experiment subjects, Lippa scanned the passing scalps, some shaved clean, some piled in colorful tresses. “It’s like a kind of art. You look at the back of people’s heads, and it’s literally like a vector field,” he says. “We assume that whatever causes people to be right-handed or left-handed is also causing hair whorl. The theory we’re testing is that there’s a common gene responsible for both.” And that gene might be a marker for sexual orientation. So, as part of his study, he has swabbed the inside cheek of his subjects. It will be months before that DNA testing is complete.

I was surprised at how many people quickly agreed to lend five minutes of their pride celebration to science. “If I could tell my mother it’s a gene, she would be so happy,” said one, Scott Quesada, 42, who sat in a chair for Lippa’s inspection.

“Classic counterclockwise whorl,” the researcher pronounced, snapping a photo.

Quesada, who is right-handed and seemed to have a typically masculinized finger-length ratio, was impressed. “I didn’t know I had a whorl at all,” he said.

By the end of the two-day festival, Lippa had gathered survey data from more than 50 short-haired men and photographed their pates (women were excluded because their hairstyles, even at the pride festival, were too long for simple determination; crewcuts are the ideal Rorschach, he explains). About 23 percent had counterclockwise hair whorls. In the general population, that figure is 8 percent.

A string of other studies, most of them conducted quietly and with small budgets, has offered up a number of other biological indicators. According to this research, for instance, gay men, like straight women, have an increased density of fingerprint ridges on the thumb and the pinkie of the left hand; and overall their arms, legs, and hands are smaller relative to stature (among whites but not blacks). There are technical differences in the way most men and most women hear, except among lesbians, whose ears function more like men’s. And there are gender-based cognitive differences in which gay men appear more like women. One involves mentally rotating a 3-D object, something males tend to do better than females—except gay men score more like straight women and lesbians function more like straight men. In navigational tasks and verbal-fluency tests, gay men and lesbians tend to have sex-atypical scores.

From these findings, it might be tempting to conclude that lesbians are universally masculinized and gay men are somehow feminized—the classic “inversion model” of homosexuality advanced by Freud. But the picture is more complicated than that. There is also evidence—some more silly-sounding than serious—that homosexuals may be simultaneously more feminine and more masculine, respectively. The stereotypes—that lesbians tend to commit to relationships early and have little interest in casual sex; that gay men have more sexual partners than their counterparts—turn out to be true. One study that supports the hyper-masculinity theory of male homosexuality involves penis size. An Ontario-based psychological researcher named Anthony Bogaert re-sorted Kinsey Institute data—in which 5,000 men answered detailed questions about their sex lives, practices, fantasies, and, it turns out, measurements of their erect organs—along sexual-orientation lines. Gay men’s penises were thicker (4.95 inches versus 4.80) and longer (6.32 inches versus 5.99). The measurements, it should be noted, were self-reported and perhaps involve reporting bias, but no one has done a study investigating whether gay men are more prone to exaggerating their assets, so, well, draw your own conclusions.

But if true, these findings negate the inversion model, Bogaert says. Instead of picturing gender and orientation along a line, with straight men and women on either end and gay people in the middle, he suggests, a matrix might be a more accurate way to map the possibilities.

Some of this work has been derided as modern-day phrenology, and obviously possessing one trait or another—a counterclockwise hair whorl here, an elongated ring finger there—doesn’t necessarily make a person gay or straight. But researchers point out that these are statistical averages from the community as a whole. And the cumulative findings support the belief now widely held in the scientific community that sexual orientation—perhaps along with the characteristics we typically associate with gayness—is biological. “We’re reaching a consensus on a broad question,” says J. Michael Bailey, a psychologist at Northwestern University. Is sexual orientation “something we’re born with or something we largely acquire through social experience? The answer is clear. It’s something we’re born with.”

Because many of these newly identified “gay” traits and characteristics are known to be influenced in utero, researchers think they may be narrowing in on when gayness is set—and identifying its possible triggers. They believe that homosexuality may be the result of some interaction between a pregnant mother and her fetus. Several hypothetical mechanisms have been identified, most pointing to an alteration in the flow of male hormones in the formation of boys and female hormones in the gestation of girls. What causes this? Nobody has any direct evidence one way or another, but a list of suspects includes germs, genes, maternal stress, and even allergy—maybe the mother mounts some immunological response to the fetal hormones.


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