Human Pheromones & Sexual Orientation Linked Brain Activity to Preferred Pheromones Linked to Sexual Preference

By Miranda Hitti
WebMD Medical News  Reviewed By Brunilda Nazario, MD on Monday, May 09, 2005


May 9, 2005 -- Swedish researchers say they've found two human pheromones that are affected by sexual orientation.

Pheromones are chemicals that stimulate animals of the same species for one or more behavioral responses, often including sexual behavior. In animal studies, choice of sexual partner is influenced by sex-specific pheromones. Researchers have long debated whether humans produce or respond to pheromones.
Two possible human pheromones have been studied by Swedish scientists including Ivanka Savic of the Karolinska Institute's neurosciences department. One chemical, called "AND," is found in men's sweat. The other, called "EST," is an estrogen-like steroid found in women's urine.

However, sexual orientation may influence the brain's response to those chemicals, say Savic and colleagues. Their findings appear in the early edition of Proceedings of the National Academy of Sciences of the United States of America.

Similar Findings in Women, Homosexual Men

Savic's study included 36 healthy homosexual men, heterosexual men, and heterosexual women (12 of each) in their mid-20s or 30s. They had similar education levels and "differed only with respect to biological sex and sexual orientation," say researchers.

Participants sniffed a variety of scents -- including AND, EST, lavender oil, and cedar oil -- while undergoing brain scans, which show activated regions.

As in an earlier experiment by Savic, the brains of heterosexual men were activated by EST but not AND. In the heterosexual women, AND but not EST activated these regions.

Among the homosexual men, activation was seen with exposure to AND but not EST. That's the same pattern as heterosexual women and the opposite of heterosexual men, say Savic and colleagues.

In all three groups, when a scent did not activate brain regions that affect sexual arousal and mood, it was still perceived by parts of the brain that process odors, the researchers say.

These studies show that our brain reacts differently to the two pheromones compared with common odors. It also suggests a link between sexual orientation and the brain, they conclude.

Savic and colleagues call for more research on the topic.

SOURCES: Savic, I. Proceedings of the National Academy of the Sciences of the United States of America, early edition, May 9-13, 2005. News release, Proceedings of the National Academy of the Sciences of the United States of America. WebMD Medical News: "Yes, Virginia, There Is a Pheromone."