Lesbians’ brains are wired differently than those of heterosexual women, reports a new scientific study.
Homosexuals’ brains respond differently from those of straight men and women when exposed to sex hormones, but researchers now say the difference is less pronounced in lesbians than in gay men. Lesbians’ brains reacted somewhat, though not completely, like those of heterosexual men, a team of Swedish researchers said in Tuesday’s edition of Proceedings of the National Academy of Sciences. A year ago, the same group reported findings for gay men that showed their brain response to hormones was similar to that of heterosexual women. In both cases the findings add weight to the idea that homosexuality has a physical basis and is not learned behavior.
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Heterosexual women found the male and female pheromones about equally pleasant, while straight men and lesbians liked the female pheromone more than the male one. Men and lesbians also found the male hormone more irritating than the female one, while straight women were more likely to be irritated by the female hormone than the male one.
All three groups rated the male hormone more familiar than the female one. Straight women found both hormones about equal in intensity, while lesbians and straight men found the male hormone more intense than the female one. The brains of all three groups were scanned when sniffing male and female hormones and a set of four ordinary odors. Ordinary odors were processed in the brain circuits associated with smell in all the volunteers. In heterosexual males the male hormone was processed in the scent area but the female hormone was processed in the hypothalamus, which is related to sexual stimulation. In straight women the sexual area of the brain responded to the male hormone while the female hormone was perceived by the scent area. In lesbians, both male and female hormones were processed the same, in the basic odor processing circuits, Savic and her team reported.
Each of the three groups of subjects included 12 healthy, unmedicated, right-handed and HIV-negative individuals.
As always with these studies, I am baffled that scientists publish findings based on such tiny sample sizes. Further, while I tend to believe homosexuality is indeed wired in the brain rather than a simple “lifestyle choice,” it’s not at all clear to me how this study sheds any light on the subject. After all, no one doubts that homosexuals are more attracted to people of the same sex than heterosexuals.
Echidne shares my questions about the survey.
More generally, that something shows up in the brain does not tell us that it always showed up in the brain the same way. Experiences we have (such as depressive illnesses) can change the way the brain reacts. What if having sex with a certain sex changes the way your brain reacts? Note that I’m not arguing against homosexuality having a physical basis. I’m arguing against the increasingly common assumption that brain scan differences are proof for a genetic explanation of behavior. Think about people who are bilingual. Their brains scan differently than the brains of monolinguals but the second language is certainly learned.
She gives her own anecdotal account of essentially “losing” her ability to differentiate the smells of cooking meats after conversion to vegetarianism.
