We already knew ovulating women have enhanced gaydar, and now there is evidence for part of how it works.

Scientists have found that heterosexual faces are slightly more symmetrical than homosexual faces, and the more heterosexual a face was rated, the more symmetrical it was. Researchers also found that faces rated more masculine tended to be rated heterosexual, confirming an overall sense that feminine male faces may somewhat accurately indicate homosexuality.

I wonder a bit about this study. Shakespeare said “God has given you one face, and you make yourself another.” I get that facial symmetry sounds like a pretty hard-coded body structure, but I still wonder how much our faces simply tell who we’ve become over the course of a lifetime. We’d have to run this test on newborns to really get accurate data.

New research demonstrates that higher brain symmetry gives gay men an enhanced ability over straight men to recall faces, a skill women typically excel at.

The same researchers found a corresponding correlation with handedness.

Left-handed heterosexuals were better at facial recognition than left-handed homosexuals and right-handed heterosexuals, which aligns with our knowledge that women and left-handed men have more bilaterally symmetrical brains than right-handed men.

Source:

• Paul Brewster, Caitlin Mullin, Roxana Dobrin, Jennifer Steeves. Sex differences in face processing are mediated by handedness and sexual orientation. Laterality: Asymmetries of Body, Brain and Cognition, 2010
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New evidence confirms a new aspect of how male children change their mother’s bodies. Scientist studied mother’s brains looking for male DNA, and found it in 63% of them, distributed across the brain and persisting through the mother’s lifetime. This means that mother’s receive DNA from their children across the placental barrier!

Not only do mothers help create gay sons, but all sons may help create their mothers. Wow.

In the past these studies measured genital arousal, an invasive procedure not everyone would want to submit to. It caused particular problems measuring the sexual response of those too young, old, or conservative to submit to typical sex research.

The new test is simpler and less invasive. Scientists show subjects erotic videos, and measure how their pupils dilate in response.

Some of the findings confirm the expected. Straight men’s pupils responded to sexual images of women, and barely responded to images of men. Straight women’s pupils responded to both, confirming Lisa Diamond’s theory that women’s sexuality is more fluid than men’s.

The most interesting finding was confirmation of the existence of male bisexuality. Contrary to previous physiological studies, bisexual men in this study had pupil dilation in response to both male and female images.

According to our pupillary responses, bisexuality exists.

Summary:

• Straight Women: Pupil dilations in response to both erotic male and female images.
• Gay Women: Pupil dilations in response to erotic female images.
• Straight Men: Pupil dilations in response to erotic female images.
• Gay Men: Pupil dilations in response to erotic male images.
• Bisexual Men: Pupil dilations in response to both erotic male and female images.

Source:

• Rieger G, Savin-Williams RC (2012) The Eyes Have It: Sex and Sexual Orientation Differences in Pupil Dilation Patterns. PLoS ONE 7(8): e40256. doi:10.1371/journal.pone.0040256

Widely reported, the initial study found that gay men’s hair tends to swirl around the crown of their head one way, while straight men’s tends to swirl the other direction. Straight men won’t admit to swirling, but a glance at their crowns shows they do. The technical term is actually whorl, and researchers looked at gay and straight men’s whorls and noted their clockwise and counter-clockwise manifestations.

Subsequent studies have not validated the hair whorl findings, and scientists are not sure hair whorls are a valid feature to count. As one says after analyzing the situation:

It’s hard to determine which way the hair whorls in people with long or curly hair, and the data do not fit the simple genetic model perfectly. So you should not use hair whorl direction to demonstrate basic genetics.

He doesn’t even mention those of us who no longer swirl around our crowns. :-(

They both tell us the same about our sexuality. Not much.

• John H. McDonald, Hair whorl: The myth

Scientists used to believe that both gender’s brains identical, but closer study in rats and humans in the 1970s and 80s revealed that some parts of the brain are have different structures for different genders. Early research then looked for brain differences between gay and straight people.

That big news came from an announcement by Dr. Simon LeVay in 1991. Examining the hypothalamus from the brains of gay men who died of AIDS, and comparing them to the brains of deceased straight men, he found that gay men’s hypothalmus’ were half the size of straight men’s, a proportion more like that of women. Although this early study was subsequently questioned, Dr. LeVay’s work opened up the study of the physiology and genetics of gay people.

One of the gendered differences is in brain symmetry. Straight women’s brains are symmetrical, with both hemispheres of equal size, while straight men are asymmetrical, with a larger right hemisphere. Swedish researchers used MRIs to compare brain hemispheres of straight and gay men and women. They found that the physical structures of gay men’s brains were more like heterosexual women’s, and lesbians brains were more like those of straight men.

Beyond brain symmetry, these researchers did positron emission tomography (PET) scans to measure blood flow to the amygdala of each hemisphere. Straight men and gay women had more nerve connections in the right side of the amygdala, while straight women gay men had more neural connections in the left amygdala. The amygdala is the center of emotional learning and memory consolidation, affecting behavior as part of our “flight, flight, or mate” response (although it is easier to remembered with three Fs, ahem). As a British scientist told the BBC:

In other words, the brain network which determines what sexual orientation actually “orients” towards is similar between gay men and straight women, and between gay women and straight men.

This Swedish study stands out for another reason. Because money for gay research is usually blocked by social conservatives, those who do gay research are often gay themselves, opening the results to charges of bias. This Swedish study was not looking for any findings on gay people. They were studying strokes, asked participants if they were gay or straight as part of the intake process, and found these results in the subsequent data.

Summary:

• Gay Men: Tend towards symmetrical brains and increased amygdala neural connections on the left side resembling straight female brain structures, indicating basic other-gender similarities from birth.
• Lesbians: Tend towards asymmetrical brains and increased amygdala neural connections on the right side resembling straight male brain structures, indicating basic other-gender similarities from birth.

• Simon LeVay, PhD, et al., A Difference in Hypothalamic Structure Between Heterosexual and Homosexual Men, Science, June, 1991
• Ivanka Savic-Berglund, MD, PhD, Proceedings of the National Academy of Sciences, June 16, 2008

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Some of the results were what we would expect. Men and women attracted to women responded positively to women’s sweat. Men and women attracted to men where attracted to straight men’s sweat. The big finding was in the participant’s reactions to gay men’s sweat. It got the strongest response: the strongest attraction from gay men, and the least attraction from others.

The study’s authors concluded that gay men produce unique odor components that heterosexual men, heterosexual women and lesbians do not, and that gay men perceive sweat odors differently as well. Some people theorize this is the root of homophobia… that there is something about gay men that is physically repellant to others. It would be interesting to find that homophobia arises from something as biological as our chemistry.

It is hard to imagine a more primal test of attraction than pit smelling. I know I’ve smelled pits that make me hot and bothered and others that make me cringe. Smell seems the essence of the magical “chemistry” we all seek in a partner, something deep in our own chemistry and wiring determines our response.

And as the study’s author said, “It’s hard to see how a simple choice to be gay or lesbian would influence the production of body odor.”

Summary:

• Gay Men: Attracted to male sweat indicating a biological root to attraction. May produce an odor repellant to those who are not gay men, a result of unknown origin but implicating a biological root to gay male-focused homophobia.
• Lesbians: Attracted to female sweat indicating a biological root to attraction.

• Charles J. Wysocki et al, Preference for Human Body Odors Is Influenced by Gender and Sexual Orientation, Psychological Science, September 2005; vol. 16, 9: pp. 694-701

To test our response to different smells researchers scanned participant’s brains while they sniffed various odors, including the androgen-like pheromones of males (AND) and estrogen-like pheromones of females (EST). Their responses to the sex hormones were predictable: lesbians and straight men were attracted to the scents of women and irritated by male pheromones, and gay men and straight women were attracted to the scents of men and irritated by female pheromones.

All test subjects were similar in age and educational levels, healthy, unmedicated, right handed, HIV negative, and had a similar reaction to ordinary odors like lavender and cedar.

This study tells us that sexual attraction comes from a deeply physiological response. Watching the brain scans, researchers noted that smells that generated a sexual response were similar in both location and degree of activation in each of the attraction pairs.

We do not know why we are attracted to the pheromones we are attracted to, but we do know it is a fundamental body function determined through genes or womb environment early in fetal development.

Summary:

• Gay Men: Attracted to male pheromones, irritated by female pheromones, indicating prenatal wiring for sexual attraction to men.
• Lesbians: Attracted to female pheromones, irritated by male pheromones, indicating prenatal wiring for sexual attraction to women.

• Ivanka Savic-Berglund, MD, PhD, Brain Response To Putative Pheromones in Lesbian Women, Proceedings of the National Academy of Sciences, May 8, 2006
• Ivanka Savic-Berglund, MD, PhD, et al., Proceedings of the National Academy of Sciences, May 2005

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

A fresco from Pompeii depicts Priapus, one of the fertility gods, weighing his penis against a bag of gold.

Much of the available evidence we have about gay male bodies demonstrates that gay men may have less exposure to testosterone in the womb than straight men, but one contrary piece of evidence comes from measuring penis size. More testosterone means a larger penis, and gay men’s penises are larger than straight men’s.

The Kinsey Institute collected data on the penises of over 5,000 men, including over 900 gay men, between 1938 and 1963. Using five different measures of length and circumference, the results showed that gay men had larger penises than straight men on all five measures.

OK, I know you want to know, so here it is: Straight men averaged 5.99 inches long, while Gay men averaged 6.32 inches. And while straight male chubbiness measured 4.80 inches, gay men’s circumference averaged 4.95 inches. So gay men are over 5% longer and 4% thicker than straight men. So much for gay men being “less man” than others. I guess homophobes will now have to mock the sissies for their longer, fatter cocks.

Summary:

• Gay Men: Longer, thicker penises indicate increased prenatal exposure to male hormones.
• Lesbians: Not applicable

Source:

• Anthony Bogaert, PhD, The Relation Between Sexual Orientation and Penile Size, Archives of Sexual Behavior, June, 1999

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Monkeys climb trees.

People attracted to men (hetero women and gay men) tend to have less long bone growth in their arms, legs and hands, than people attracted to women (hetero men and lesbians).

The theory is that those with longer arm, leg, and hand bones had more exposure to androgens in the womb, and those with shorter bones had less.

Summary:

• Gay Men: Shorter leg, arm, and hand bones in proportion to height indicates lower exposure to male hormones in the womb.
• Lesbians: Longer leg, arm, and hand bones in proportion to height indicates higher exposure to male hormones in the womb.

• Martin, J. T. and D. H. Nguyen. 2004. Anthropometric analysis of homosexuals and heterosexuals: implications for early hormone exposure, Hormones and Behavior 45: 31-39

Researchers into the eye blink response startle their subjects with a loud noise, then rate the response on the prepulse inhibition (PPI) scale. These hard-wired responses give us a view into the limbic system or “the emotional brain” that helps control emotion, behavior, long-term memory, and smell. The limbic system is also highly interconnected with the brain’s pleasure center meaning it plays an important part in sexual arousal and the high of some recreational drugs. The limbic system also processes memory, tagging certain experiences as having special significance.

Lesbians have a strong blink response, closer to the response of straight men. Gay men’s responses are weaker than straight men’s, but not so dramatically.

One of the study’s author explained why this is important:

The startle response is pre-conscious and cannot be learned. It is mediated by an ancient region of the brain called the limbic system which also controls sexual behavior. This is very strong evidence that female sexual orientation at least may be ‘hard-wired’ in this region.

Summary:

• Lesbians: Strong blink response resembling straight men’s indicates prenatal hard-wiring of the limbic system.
• Gay Men: Weaker blink response than straight men, but the differentiation is minor.

• Qazi Rahman, PhD, et al., Behavioral Neuroscience, Oct. 2003

We think of our ears picking up sounds, but don’t consider that inner ear makes sounds too. As the tiny bones of the inner ear move, they give off gives off weak clicking sounds called “otoacoustic emissions.” Listening to inner ear clicks offers scientists a non-invasive way to study of prenatal hormones on the body.

As one of the most delicate mechanisms of the body, the inner ear is highly vulnerable to womb conditions. In general, men don’t hear sounds as well as women, an effect created by prenatal exposure to male hormones that affects the cochlea. Straight women’s cochleas are three times more sensitive than men’s. Maybe that explains all those men who can sleep through the baby fussing in the night?

Lesbian and bisexual women’s inner ears emitted less frequent and weaker sounds than heterosexual women’s. Lesbian’s inner ears are one third as sensitive as straight women’s, meaning their inner ear structures are closer to men’s. The study’s author notes that for lesbians, “Their auditory centers have been masculinized, and the presumption is that so have the sites in the brain that direct sexual preference.” Knowing that lesbians tend to have masculinized inner ears, we can deduce that other parts of their bodies and brains must be affected as well.

This effect was not found in gay men, as we have the same otoacoustic emmisions as straight men.

Summary:

• Lesbians: Weaker otoacoustic emissions indicates higher prenatal exposure to male hormones.
• Gay Men: No differentiation observed.

• Dennis McFadden, PhD, et al., Proceedings of the National Academy of Sciences, Mar. 1998

Queer handedness

Handedness is interesting because we can see patterns in people, but don’t know what makes me right handed and some other person left handed (and we won’t even get into the ambidextrous). Current theories on handedness include genetics, birth stress, ultrasound, and prenatal testosterone. We also know body asymmetry correlates with gendered cognition, so we surmise there may be a relationship between cognition and handedness.

The other confusing thing is that varying studies have come up with conflicting results. One study only found the effect in gay women, while another only found it in gay men. Adding further confusion, the more older brothers a boy has, the more likely he is to be gay, but this is only true for right-handed males. Left-handed males are only more likely to be gay if they have no older brothers. Right-handed males without older brothers, and left-handed males with older brothers, were homosexual at about the same rate.

Clearly something is going on here, but more study is figure out exactly what!

Summary:

• Gay Men: Tend towards left-handedness. No older brother effect for right-handed gay men.
• Lesbians: Tend towards left-handedness.

Sources:

• Lalumière ML, Blanchard R, Zucker KJ., Sexual orientation and handedness in men and women: a meta-analysis. Psychol Bull. 2000 Jul;126(4):575-92. A meta-analysis of 20 previous studies showing gay people are somewhat more left handed than straight people.
• Mustanski, B. S., Bailey, J. M., & Kaspar, S. (2002). Dermatoglyphics, handedness, sex, and sexual orientation. Archives of Sexual Behavior, 31, 113–122. Found that homosexual women to be more left handed that straight women, but did not find the same effect in heterosexual and homosexual men.
• Lippa, R. A. (2003). Handedness, sexual orientation, and gender-related personality traits in men and women. Archives of Sexual Behavior, 32 103–114. Found homosexual men more left handed than heterosexual men, but did not find the same effect in women.
• Blanchard, R., Cantor, J. M., Bogaert, A. F., Breedlove, S. M., & Ellis, L. (2006). Interaction of fraternal birth order and handedness in the development of male homosexuality. Hormones and Behavior, 49, 405–414. Found the older brother effect in handedness.

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

You already know that every individual has a unique fingerprint, but did you know these fingertip swirls are usually asymmetrical? Most of us have more fingertip ridges on our right hands than our left.

Gay people are different. We tend to have higher left hand ridge counts. 30% of us have more fingertip ridges on our left, whereas only 14% of straight people have more on their left hands.

Fingertip swirles seem an odd thing to count, but they tell us something important. Fingertip patterns are highly inheritable, with genetics accounting for 90%–95% of the variation. Our fingerprint swirls are also fully developed by the 4th month of pregnancy, meaning this trait is not affected by other factors in birth, childhood, or later in life.

Body asymmetry is important because it correlates with the ability to perform certain cognitive tasks. Those with higher right hand counts excelled at tasks where men typically excel, and those with higher left hand counts excelled at tasks where women typically excel. Knowing the link between asymmetry and cognitive functioning we learn that fingertip swirl counts tells us there are gender or sexual-orientation related cognitive patterns based in our DNA, factors determined at the moment of conception.

Summary:

• Gay Men: Tend towards higher fingerprint ridge counts on the left hand indicating pre-natal differentiation.
• Lesbians: Same effect as gay men.

Source:

• J.A.Y. Hall and D. Kimura, Dermatoglyphic asymmetry: Relation to sex, handedness and cognitive pattern, (1994) Behavioral Neuroscience, 108, 1203-1206

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Preston left, Kamran right.

If I hold out my hand, I can see that my ring finger and my index finger are about the same length. That may be a sign of my body’s homosexuality. In general, men tend to have longer index fingers than ring fingers, while women’s index fingers tend to be the same size or slightly shorter than their ring fingers.

While finger length sounds like a random data point, it isn’t. The length of our fingers is determined by the amount of testosterone we receive in the womb. Apparently I had less, resulting in feminized finger lengths, while Kamran had the normal amount. This jibes with the concept these are statistical probabilities or tendencies, not absolutes. Lesbians tend towards men’s finger lengths, a sign of a masculinized body.

Strangely, none of this applies to gay men with more than one older brother. As the oldest of five kids, this doesn’t apply to me.

I really enjoy how we learned all this. With serious funding of gay people blocked, researchers went out into public street fairs, asked participants to complete a questionnaire about their sexuality, and then photocopied their hands for measurement later. The triumph of the copying machine as scientific research tool.

Summary:

• Gay men: Finger length tends towards female patterns, indicating lower testosterone exposure in the womb. The pattern is not seen in gay men with more than one older brother.
• Lesbians: Finger lengths tend towards male patterns, indicating higher testosterone exposure in the womb.

Source:

• S. Marc Breedlove et al, Finger-length ratios and sexual orientation, (2000) Nature, 404, 455 – 456

This article is part of a series, Written on the Body, exploring the correlations between our body structures and sexual attraction.

Looking puzzled at about 12 years old

I bring all that up because I am gay through some amalgam of body and soul. How much of my sexuality is from a “gay spirit” and how much was a biological destiny written on my bones, I don’t know, or really care. I am what I am, regardless of how I got here.

That said, it is still pretty fascinating to see the correlations between gay bodies and sexual attraction. Keeping it simple, we can look at what is physically different about gay bodies, and consider why these differences occur. The current list of variations we’ve discovered includes:

• Finger length
• Fingerprints
• Left or right handedness
• Inner ear clicks
• Eye blink reactions
• Bone length in the legs, arms, and hands
• Penis size
• Response to pheromones
• Response to sweat
• Brain structures
• …and hair swirls (oh. really? no? ok. um, not.)

For a list of all articles on gay bodies click here.

Some of my ancestors floating in the Great Salt Lake around 1926. The guy in the back was a family friend. People use to take the train out to the Great Salt Lake for a day at the Saltair resort, therefore the matching swimsuits. No implication of anyones sexuality implied, I just enjoyed the photo of brothers.

We don’t know why, but there’s an interesting theory. When a mother has a series of boys, and becomes pregnant with another male, her body may have an immune system response that affects fetal development, including sexual differentiation of the brain. This could be a reaction of her female body reacting to a series of male embryos or it could be an evolutionary adaptation to ensure there is a feminized boy in the family if girls fail to appear.

A later study validated the results, and added the calculation that each older brother increases the chances the next son is homosexual by 33%. At an average rate of homosexual orientation of 4%, it would take 9-10 older brothers to reach a 50-50 chance of being gay.

Summary:

• Gay Men: The more older brothers, the more likely a son is gay.
• Lesbians: No sibling effect observed.

• R. Blanchard and A.F. Bogaert, Proportion of homosexual men who owe their sexual orientation to fraternal birth order: an estimate based on two national probability samples, Am. J. Hum. Biol. 16 (2004), pp. 151–157.
• R. Blanchard, Quantitative and theoretical analyses of the relation between older brothers and homosexuality in men, J. Theor. Biol. 230 (2004), pp. 173–187.

A human female ovary, just before an egg is released...the moment when a woman's gaydar is most acute.

Some people say we are not all wired for this whole gay thing, yet it appears women are hard wired with some seriously practical gay awareness.

Mr. Bonobo (photo by Ltshears via Wikimedia Commons)

Interestingly, numerous studies show that bonobos maintain a peaceful society by using sex as an alternative to conflict in their social relations. When researchers put a new and intriguing object into a cage with two female bonobos, they will often have sex with each other before they approach the gift, presumably for stress release.

Meanwhile, in humans, one of the puzzles of human physiology is why the female’s main sensory spot is located separately from the place of direct sexual contact. In males the pleasure center is at the end of the penis, which is why men can happily stick it into just about anything. This motivates men to have sex with women–he derives pleasure from putting his cock into a vagina. But the female is not similarly wired for direct pleasure in intercourse. The orgasmic functions are particularly complex, largely because of the clitoris’s location. But why?

One answer is that the male is already motivated for sex and the resulting procreation, leaving the female body free to evolve for other purposes. The famous primatologist Frans de Waal wrote in 1995, “The frontal orientation of the bonobo vulva and clitoris strongly suggest that the female genitalia be adapted for this [frontal] position.” In her book Evolution’s Rainbow, Stanford biologist Joan Roughgarden notes that,

From the standpoint of female reproduction, little is gained by placing the clitoral neurons near the vagina to further same-sex mating when males are well motivated for intercourse anyway. Instead, the pleasure neurons are shifted to a location that promotes same-sex mating and may yield more effective same-sex bonds, increasing overall Darwinian fitness at no reproductive cost.

(photo by Malloreigh via Flickr)

The mind reels. Could it be that human females evolved a frontal clitoral pleasure center because female-female sexual bonding was so vital to our development? Do human males favor the missionary position because of the ways lesbian bonding affected female bodies? And most importantly to men who want to please their partners, is the clitoris separated from the vagina for reasons that have nothing to do with men? This explains a lot of male frustration in chasing elusive female orgasms, as men are fighting a battle nature rigged for the other team. We can conclude that if men get pleasure wherever they put their penis, and women are designed to find pleasure each other, we end up with a same-sex twist on a classical formulation: men sow their seed, and women bond…with each other.

Overwhelming as it seems, every human female body may be a testament to the power and importance of same-sex bonding in women.

Jesse Bering

Mr. Bering is a research psychologist, and while the human issues he writes about are all over the map, he often focuses on human sexuality in a way that is both scientific and warm. This week’s column takes a fascinating look at the psychological effects of ingesting semen.

It turns out that semen (not sperm, which is the little swimmers, but semen, which is the white goo the spermies travel in) has got some pretty interesting ingredients:

Such anxiolytic chemicals include, but are by no means limited to, cortisol (known to increase affection), estrone (which elevates mood), prolactin (a natural antidepressant), oxytocin (also elevates mood), thyrotropin-releasing hormone (another antidepressant), melatonin (a sleep-inducing agent) and even serotonin (perhaps the most well-known antidepressant neurotransmitter).

No wonder women and gay men get hooked on the stuff, with profound implications about why we desire sexual congress. It makes me wonder about people with sex addictions. Read the whole article, fascinating.