WASHINGTON, D.C. New research suggests that sexual orientation is biological.
According to a team of Swedish researchers, lesbians' brains reacted somewhat, though not completely, like those of heterosexual men, when exposed to sexual hormones.
That's in line with an earlier study that indicated gay men's brain responses were different from straight men, though the difference for men was more pronounced than has now been found in women.
In both cases the results add weight to the idea that homosexuality has a physical basis and is not learned behavior.
The findings are in today's edition of Proceedings of the National Academy of Sciences.