Sexual Orientation: In The Brain

Study Finds Brain Differences In Reaction To Testosterone Scent

(AP)  The response in gay men and straight women was concentrated in the hypothalamus with a maximum in the preoptic area that is active in hormonal and sensory responses necessary for sexual behavior, the researchers said.

And when estrogen, the female hormone was used, there was only a response in the olfactory portion of the brains of straight women. Homosexual men had their primary response also in the olfactory area, with a very small reaction in the hypothalamus, while heterosexual men responded strongly in the reproductive region of the brain.

Savic said the group is also doing a study involving homosexual women but those results are not yet complete.

In a separate study looking at people's response to the body odors of others, researchers in Philadelphia found sharp differences between gay and straight men and women.

"Our findings support the contention that gender preference has a biological component that is reflected in both the production of different body odors and in the perception of and response to body odors," said neuroscientist Charles Wysocki, who led the study.

In particular, he said, finding differences in body odors between gay and straight individuals indicates a physical difference.

It's hard to see how a simple choice to be gay or lesbian would influence the production of body odor, he said.

Wysocki's team at the Monell Chemical Senses Center studied the response of 82 heterosexual and homosexual men and heterosexual and homosexual women to the odors of underarm sweat collected from 24 donors of varied gender and sexual orientation.

They found that gay men differed from heterosexual men and women and from lesbian women, both in terms of which body odors gay men preferred and how their own body odors were regarded by the other groups.

Gay men preferred odors from gay men, while odors from gay men were the least preferred by heterosexual men and women and by lesbian women in the study. Their findings, released Monday, are to be published in the journal Psychological Science in September.

The Swedish research was funded by the Swedish Medical Research Council, the Karolinska Institute and the Magnus Bergvall Foundation. Wysocki's research was supported by the Monell Center.