Women Risk Risky Sex at Worst Time

Nov. 7, 2007 -- Women are most attracted to sex with masculine, high-risk men during ovulation, when they are most likely to get pregnant, a Kinsey Institute study suggests.

Heather Rupp, PhD, a research fellow at the Kinsey Institute, studied 12 single heterosexual women aged 23 to 28. While hooked up to an fMRI machine that detects activity in different parts of the brain, the women looked at 256 photos of male faces.

Using a computer morphing program, researchers altered the photos to make the male faces look more or less masculine. The women were also given sexual risk information on the men that included their number of sexual partners and their typical condom-use patterns.

After viewing the faces and the information, the women were asked to rate how likely they were to have sex with the man in each photo.

But in this study, Rupp and colleagues weren't as much interested in who the women said they'd have sex with as in what happened inside their heads.

Around the time of ovulation, when the women were most likely to conceive after unprotected sex, the women's brains showed more activity in areas linked to reward and risk taking. Stimuli that arouse this area of the brain include drugs, alcohol, and gambling.

During ovulation, the women also had weaker brain responses in brain areas linked to inhibition and risk evaluation. And while women showed more activity in brain areas linked to decision-making and reward when looking at photos of high-risk men than when looking at photos of low-risk men, this activity was weaker during ovulation than it was later in the menstrual cycle.

At this week's annual meeting of the Society for Neuroscience, Rupp suggested that during ovulation, women may be more likely to engage in risky sex and be more vulnerable to drug and alcohol abuse than at other times.

"At ovulation, when is likely, women may prioritize fertilization and find masculine men more rewarding and less risky," Rupp suggested in her meeting presentation. "Towards the end of the menstrual cycle, when hormones are preparing for potential pregnancy, the priority may shift from mating to finding a low-risk, stable partner who can provide more parental investment and resources."

(Do you believe that you lose your inhibitions when you ovulate? Tell us about it on WebMD's Women's Health: Friends Talking message board.)