Why We Cheat

Infidelity is a hot topic of conversation, but being faithful does have its merits.

By Martin Downs
WebMD Feature

Reviewed By Brunilda Nazario, MD

Sexual infidelity is one of humanity's great obsessions, perhaps second only to violence. We abhor it, yet we want to hear all about it, and some can't resist it. It's what has kept Jerry Springer on TV for the past 14 years and Greek mythology alive in the retelling for the past 3,000.

In one story after another, mundane and epic, we are reminded of the emotional and social fallout of messing around. That's in addition to the scowls it gets from the world's biggest religions. Why, then, is monogamy so hard for so many?

Perhaps for humans, monogamy does not come naturally, and biology predisposes us to seek multiple sex partners. That's what zoologist David Barash, PhD, and psychiatrist Judith Lipton, MD, argue in their book, The Myth of Monogamy: Fidelity and Infidelity in Animals and People. Virtually all animals, they say, are far from being 100% monogamous 100% of the time.

"The only completely, fatalistically monogamous animal we've been able to identify is a tapeworm found in the intestines of fish," Lipton tells WebMD. That's because the male and female worms fuse together at the abdomen and never separate afterward.

Other animals, including humans, are motivated to ensure their reproductive success not only by picking the highest quality mate they can get but also by taking others on the side.

"The examples where monogamy is perceived to be the norm are generally facades when you actually do DNA testing and see who's sleeping with whom," Lipton says. She and Barash make a distinction between sexual fidelity and what they call "social monogamy." Even in animals that mate for life, like many birds do, DNA tests reveal that the offspring are often not related to the male of the pair.

That is the case with people, too. Lipton says she was once contacted by a Canadian hospital, where doctors were running genetic tests to find out children's risks for inherited diseases. In about 10% of the samples, the children were not genetically related to the supposed father.

But make no mistake: Lipton and Barash, who have been married to each other for 28 years, don't say that sexual fidelity is impossible or wrong because it is not natural, only that it takes some effort. "We human beings spend a large part of our lives learning to do unnatural things, like play the violin or type on a computer," Lipton says.

The Flawed and the Faithful

If fidelity is a matter of skill, then why are some talented and others terribly clumsy?

People who enter into long-term monogamous relationships, and who really keep their promises, "tend to be very healthy mentally," Peter Kramer, MD, tells WebMD. Kramer, a psychiatrist, is the host of The Infinite Mind on NPR and author of Listening to Prozac, Should You Leave? and most recently, Against Depression.

"There are lots of things that they're not, and that makes it possible for them to do this thing that may be in some ways difficult," he says.

Don-David Lusterman, PhD, a marriage and family therapist and author of Infidelity: A Survival Guide, says he thinks some people who cheat are what he calls "pursuers," who are also called womanizers when they are men. "They tend to require great numbers of conquests and they perceive them as conquests," Lusterman tells WebMD. "I see that as a developmental flaw in an individual, as opposed to an affair frequently being a function of some disruption in the couplehood. They're very different things."

In clinical terms, he says, pursuers often have a narcissistic personality disorder. They crave and demand affection and attention but are not able to return it in kind.

Those who aren't pursuers may be susceptible to an affair because they are not aware that something is amiss or lacking in the relationship. Given the attention of another man or woman, "they just suddenly feel more special," says Luanne Cole Weston, PhD, a psychologist and expert moderator of WebMD's Sex MattersŪ message boards. "They ceased to feel as special in their own first relationship."

Others are well aware of their frustration and they actively seek what they want outside the relationship. "I do hear some variation of that quite frequently," Priya Batra, PsyD, a women's health psychologist in the Kaiser Permanente health care system, tells WebMD.

The proverbial midlife crisis can be another trigger for cheating, "And then you have the younger person who hasn't tasted enough of everything who maybe committed prematurely," Weston says.

Infidelity by the Numbers

A lot of the statistics on infidelity floating around are dubious. Some say that as many as 50% of women cheat on their husbands, and 70% of men step out on their wives.

More reliable and believable data come from the University of Chicago's National Opinion Research Center. About 15% of women surveyed in 2002 said they'd ever had sex with someone besides their spouse while married, and 22% of men had. Roughly 2% of women and 4% of men had done so in the past year.

It's clear that men are more prone to infidelity, and notably, the longer they live, the more likely they are to cheat. According to the 1992 National Health and Social Life Survey, 37% of men aged 50-59 had ever had an extramarital affair, compared with just 7% of men aged 18-29. The men's percentages went up steadily in each age range, whereas for women, the most perfidious were the baby boomers, born between 1943 and 1952. About 20% of them reported ever having had an affair, but in all other age ranges, infidelity hovered between 11% and 15%.