Women: A World of Turn-ons

To compare men and women's sexual responses, Meredith Chivers, then a psychologist at Northwestern University, asked heterosexual men and women to lounge in a recliner in a dimly lit room. Each person separately watched back-to-back episodes of six erotic films -- gay men, gay women, straight men and women, and one video of mating primates.

Chivers monitored each participant's physical and emotional response to the films, using gadgets attached to their genitals to monitor blood flow, a sign of arousal. Participants gave a subjective rating to each sex scene by adjusting a 180-degree lever -- 0 meaning no arousal and 180 indicating full turn-on.

Although the women said the primate and lesbian flicks weren't exciting, their vitals told a different story. In contrast, the men's brains and penises were right in line -- they weren't aroused by the primates and responded most to the heterosexual films.

Why are women's bodies ready for sex when their brains aren't? Chivers speculates that the response may be an evolutionary adaptation that protects women from injury and infection in instances when sex was forced upon them.
The results appear in Biological Psychology.