Swedish researchers are reporting today that brain patterns in homosexual people resemble those seen in heterosexual members of the opposite sex, a finding that will add to the debate about the origins of homosexuality.
In the new study, to be published later today in the Proceedings of the National Academy of Sciences, scientists at the Karolinska Institute describe brain scans taken of 90 people, 50 heterosexuals and 40 homosexuals, split evenly by gender.
They found that the brains of homosexual men and heterosexual women were more symmetrical than the brains of heterosexual men and homosexual women. A similar difference emerged when the researchers looked in particular at the amygdala, a brain region associated with emotional reactions. Heterosexual women and homosexual men had more connections between their right and left amygdala and more connections with other brain regions than did homosexual women and heterosexual men.
Scientists have spent decades looking for brain differences between homosexual and heterosexual people and since the early 1990s have been finding anatomical distinctions in regions associated with sexual behavior. The new study suggests broader brain differences between homosexual and heterosexual men and women, even in regions not linked to sexual attraction. —Richard Monastersky