Brain scans have provided the most compelling evidence yet that being gay or straight is a biologically fixed trait.

The scans reveal that in gay people, key structures of the brain governing emotion, mood, anxiety and aggressiveness resemble those in straight people of the opposite sex.

The differences are likely to have been forged in the womb or in early infancy, says Ivanka Savic, who conducted the study at the Karolinska Institute in Stockholm, Sweden.

“This is the most robust measure so far of cerebral differences between homosexual and heterosexual subjects,” she says.

Previous studies have also shown differences in brain architecture and activity between gay and straight people, but most relied on people’s responses to sexuality driven cues that could have been learned, such as rating the attractiveness of male or female faces.

Source: Gay brains structured like those of the opposite sex