"It is surprising that the wives and husbands and girlfriends aren't more suspicious," says Lever. "Even when they know something's amiss —a sex life that's fizzled or intimacy waning—they count on their partner's love to keep them from straying."
Philanderers are so inscrutable partly because there’s no single profile for a cheater.
The survey did find some common scenarios, however.
Cheating tends to happen well into the relationship—especially in the three- to five-year zone—by a man who is dissatisfied with his sex life or a woman who feels emotionally deprived. The new lover is most often a friend or co-worker, and the typical fling lasts less than a week.
"It can be the 30-year-old guy who's been cohabiting for six years with his girlfriend, or the 45-year old guy who has seemed happily married for 15 years, or, perhaps most surprising, it's the young mom who seems totally wrapped up with her infant and toddler," says Lever.
Indeed, having kids is no deterrent. According to the survey, 15 percent of women and 16 percent of men with children ages 2 to 5 years had an affair. An unexpected 7 percent of women and 9 percent of men cheated while there was a baby under the age of 2 in the home.