Gay men "attracted by same odours as women"

(AFP) Homosexual men respond in the same way as women to pheromones, or odors believed by many to regulate sexual arousal, a new Swedish study shows, lending credence to the theory that homosexuality is biologically determined.

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"We found that homosexual men react the same way as women do to the (testosterone derivative) androstadien pheromone: they get aroused," said Per Lindström, a physician at the neuroscience department at the Karolinska University Hospital and the co-author of a new study on the subject.

The report, titled "Brain response to putative pheromones in homosexual men", reveals that gays, unlike heterosexual men, are not aroused by the female pheromone estratetraen but are instead turned on by the same odors that get straight women's juices flowing.

"This shows that reactions to these pheromones are not linked to gender but to sexual preference," Lindström told AFP, admitting that the study of human pheromones is controversial.

While experts agree that pheromones in animals influence the behavior and often function as an attractant of the opposite sex, there is no consensus on what role the chemical stimulant plays in human relations.

"It is not yet generally accepted that humans have a pheromonal system at all," Lindström said, insisting however that his research has shown a clear link between pheromones and sexual attraction.

When a heterosexual woman senses androstadien pheromones, which have a nearly undetectable odor, the part of her brain that governs sexual arousal is activated. If she senses pheromones from another woman however, only her sense of smell is triggered, he said.

"We believe that our studies lend more credence to the biological explanation model than to a psychological one when it comes to homosexuality. And this result can also help remove the feeling of guilt that still often accompanies homosexuality," Lindström said in an interview on Swedish public radio.

For the study, which was published on Monday in scientific publication Proceedings of the National Academy of Sciences of the United States of America, or PNAS, researchers used a complex brain imaging technique to measure the level of arousal in heterosexuals and gays when exposed to the same pheromones.

Four test groups, consisting of 12 individuals each, were examined: one made up of heterosexual men, one with gay men, one with heterosexual women and one with homosexual women.

"This is a very complex and very expensive technology, so we couldn't afford and didn't have the time to conduct the tests on larger groups," Lindström told AFP, claiming that the research had nonetheless been conclusive.

Lindström and the two other co-authors of the report, Ivanka Savic and Hans Berglund, are currently working on a follow-up study on how lesbians react to female pheromones.