Department of Sexual Predestination
An article a few weeks ago in the Economist — "Dyed in the womb: A lesbian's sexual identity seems to be established before birth" — reported on a fascinating study done by a researcher at the University of East London, in England, that found that lesbians blink like heterosexual men. As the Economist observes: "That, in turn, suggests that the part of their brain that controls this reflex has been masculinised in the womb."
The basis for the research was as follows: "Anyone who is startled by an unexpected noise tends to blink. If, however, the startling noise is preceded by a quieter sound, this blink is not so vigorous as it would otherwise have been. It is this lack of vigour which differs between the sexes. Men blink less vigorously than women when primed in this way."
So Dr. Qazi Rahman and his team sat a bunch of men and women, gay and straight, down in a room, wired up their blinking muscles, and made noise. Lo and behold, they found that, statistically, lesbians blinked more like straight men than straight women.
If you want to read more about why this is so, chemically, you can read the paper here, in the October 2003 issue of Behavioral Neuroscience.
I myself have never bought the argument that being gay was a "lifestyle" choice. But maybe that's because my opinions were "liberalized" in the womb!