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Study: gays’ brain symmetry resembles other sex
June 16, 2008
Courtesy PNAS
and World Science staff
Researchers have found that gay people’s brains resemble those of the opposite sex in some ways, including the extent to which the brain’s sides are symmetric. Amygdala activity in (top
to bottom rows) heterosexual men, heterosexual women, homosexual
men and homosexual women. (Image courtesy PNAS)
Some psychological tests have shown differences between men and women in how much they use
each of the brain’s hemispheres, or opposite sides, in verbal tasks.
Other research has hinted that homosexuals exhibit the tendencies of the opposite sex in brain behavior unrelated to sexual activity.
In the new study, Ivanka Savic of the Karolinska Institute in Stockholm and colleague per Lindström found that the brains of
heterosexual men and homosexual women are slightly asymmetric:
the right hemisphere is larger than the left.
But the brains of gay men and straight women are not, they found.
The scans also revealed differences in the way the amygdala—a brain structure important for emotional learning—is connected to the rest of the brain, the researchers reported. In these connections, they said, gay men resemble straight women, and lesbians straight men.
A possible explanation is that the amygdala in the latter group is wired for a greater “fight-or-flight” response, said the researchers, who analyzed the brains of 90 subjects.
The scientists used the scanning method known as magnetic resonance imaging or MRI to assess brain size, as well as additional data from a separate scanning method called positron emission tomography or PET.
The findings are published in this week’s early online edition of the research journal
Proceedings of the National Academy of Sciences.
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Researchers have found that gay people’s brains resemble those of the opposite sex in some ways, including the extent to which the brain’s sides are symmetric. Some psychological tests have shown differences between men and women in how much they use the brain’s hemispheres, or different sides, in verbal tasks. Other research has hinted that homosexuals exhibit the tendencies of the opposite sex in brain behavior unrelated to sexual activity. In the new study, Ivanka Savic of the Karolinska Institute in Stockholm and colleague Per Lindström found that the brains of heterosexual men and homosexual women are slightly asymmetric—the right hemisphere is larger than the left. But the brains of gay men and straight women are not, they found. The scans also revealed differences in the way the amygdala—a brain structure important for emotional learning—is connected to the rest of the brain, the researchers reported. In these connections, they said, gay men resemble straight women, and lesbians straight men. A possible explanation is that the amygdala in the latter group is wired for a greater “fight-or-flight” response, said the researchers, who analyzed the brains of 90 subjects. The scientists used the scanning method known as magnetic resonance imaging or MRI to assess brain size, as well as additional data from a separate scanning method called positron emission tomography or PET. The findings are published in this week’s early online edition of the research journal pnas.