Biological differences in gay men and lesbians
[edit] Physiological
Recent studies have found notable differences between the physiology of gay people and non-gay people. There is evidence that:
* Gay men have similar brains to those of straight women and gay women to those of straight men [48]
* The average size of the INAH-3 in the brains of gay men is approximately the same size as INAH 3 in women, which is significantly smaller, and the cells more densely packed, than in heterosexual men's brains.[5]
* The suprachiasmatic nucleus was found by Swaab and Hopffman to be larger in gay men than in non-gay men,[49] the suprachiasmatic nucleus is also known to be larger in men than in women.[50]
* The anterior commissure is larger in women than men and was reported to be larger in gay men than in non-gay men,[51] but a subsequent study found no such difference.[52]
* Gay men report, on an average, slightly longer and thicker penises than non-gay men.[53]
* Gay men's brains respond differently to fluoxetine, a selective serotonin reuptake inhibitor.[54]
* The functioning of the inner ear and the central auditory system in lesbians and bisexual women are more like the functional properties found in men than in non-gay women (the researchers argued this finding was consistent with the prenatal hormonal theory of sexual orientation).[55]
* The startle response (eyeblink following a loud sound) is similarly masculinized in lesbians and bisexual women.[56]
* Three regions of the brain (medial prefrontal cortex, left hippocampus, and right amygdala) are more active in gay men than non-gay men when exposed to sexually arousing material.[57]
* Gay and non-gay people emit different armpit odors.[58]
* Gay men are more likely to have a counter-clockwise hair whorl pattern.[59]
* Gay and non-gay people's brains respond differently to two human sex pheromones (AND, found in male armpit secretions, and EST, found in female urine).[60][61][62]
* Finger length ratios between the index and ring fingers may be different between non-gay and lesbian women.[63][64][55][65][66][67]
[edit] Cognitive
Recent studies suggest the presence of subtle differences in the way gay people and non-gay people process certain kinds of information. Researchers have found that:
* Gay men and lesbians are significantly more likely to be left-handed or ambidextrous than are non-gay men and women;[68][69][70] Simon LeVay argues that because "[h]and preference is observable before birth[71]... [t]he observation of increased non-right-handness in gay people is therefore consistent with the idea that sexual orientation is influenced by prenatal processes," perhaps heredity.[5]
* Gay men[72] and lesbians are more verbally fluent than heterosexuals of the same sex[73][74][75] (but two studies did not find this result).[76][77]
* Gay men may receive higher scores than non-gay men on tests of object location memory (no difference was found between lesbians and non-gay women).[78]
