Cover Story

Northwestern University psychologist J. Michael Bailey, PhD, says he is used to getting attention, both positive and negative, for his research on sexual orientation. "It always provokes mixed reactions," he says.

But when an article titled "Federally funded study measures porn arousal" appeared in The Washington Times last December and described in unflattering terms a study conducted with his graduate student Meredith Chivers, he was unusually frustrated, he says. Conservative radio and television shows picked up the story, but because the study was under review, he couldn't explain why it wasn't the boondoggle it had been made out to be.

The purpose of the study, says Bailey, was to explore a basic question about the relationship between sexual arousal and sexual orientation that has its roots in studies conducted in the 1960s. That research, says Bailey, showed that heterosexual and gay men could be distinguished on the basis of their erectile response to pictures of nude men and women. The effect is so robust, he notes, that it can be used forensically to detect men's sexual orientation, and it probably plays a significant role in shaping men's self-identification as gay or heterosexual.

But similar research on women has not been conducted until very recently. Now, however, new evidence has emerged to suggest that "category specificity," as Bailey calls it--the tendency for gay men to become aroused only to same-sex images and heterosexual men to become aroused only to opposite-sex images--is not true of women. If so, it means there are fundamental sex differences in the relationship between arousal and orientation.

In their study, Chivers and Bailey showed erotic films to heterosexual, bisexual and lesbian women while measuring their genital and subjective arousal. They found that women, unlike men, showed the same genital responses to different kinds of erotic stimuli regardless of their sexual orientation, says Bailey. Whether the films depicted two males, two females, or a male and a female engaging in sexual activity, the different groups of women in the study responded similarly.

"The main message is that there is a very fundamental sex difference between sexual arousal patterns in men and women," says Bailey. The difference has implications for understanding both the phenomenology of sexual orientation--what it's like to be straight, gay or lesbian--and the process by which people learn about their orientation, says Bailey.