Extramarital affairs are not so common.

Married couples may not be fooling around with other partners as frequently as some people think, Michael Wiederman, a psychological sciences professor at Ball State University, Muncie, Ind., says. A national survey of 2,000 married men and women revealed that incidents of extramarital affairs are far fewer than Hollywood and adult magazines suggest About 22% of men and 11% of women admitted to having an affair during their lifetimes. On the other hand, several popular publications, such as Playboy and Cosmopolitan, found in their surveys that half of all men and a third of women admit to having extramarital sex.

Wiederman found that young men and women are less likely to have had affairs, while people in their 40s and 50s had the highest rates. "Young people have been married only a short time, while older people have more opportunities over the years to engage in such activities. Older women were the least likely to have affairs. These women, usually in their 60s and older, come from a generation when extramarital affairs were...