Infidelity and the Science of Cheating

Why do men find sexual infidelity by their mates so distressing? Why do women find emotional infidelity so threatening? The new view blames it all on our genetic inheritance, a faddish intellectual trend that is likely to gain momentum in the coming years.

Think of a committed romantic relationship that you have now, or that you had in the past. Now imagine that your spouse, or significant other, becomes interested in someone else. What would distress you more:

Discovering that he or she has formed a deep emotional attachment to the other, confiding in that person and seeking comfort there rather than from you?

Discovering that your partner is enjoying daily passionate sex with the other person, trying positions rarely seen outside the Kamasutra?

While this makes for an interesting party game--though we don't advise trying it around the family Christmas table--the question has a more serious purpose. Researchers have been using such ""forced choice'' experiments to probe one of the more controversial questions in psychology: why do more men than women say sexual betrayal is more upsetting, while more women than men find emotional infidelity more disturbing? Psychologist David Buss of the University of Texas, Austin, first reported this gender gap in 1992. Since then other researchers have repeatedly found the same pattern. But when it comes to explaining why men and women differ, the battle rages.

The year now ending brought claims that genes inherited from our parents make us risk takers or neurotic, happy or sad. In the new year, watch out for ever more studies on how genes passed down from Neanderthal days make us what we are. ""There is tremendous interest in evolutionary perspectives in psychology,'' says John Kihlstrom of Yale University, editor of the journal Psychological Science. And not just among scientists. In 1996, magazine articles waxed scholarly on how evolution explains, for instance, Dick Morris's extramarital escapades. Basically, his DNA made him do it.

The debate shapes up like this. Evolutionary psychologists argue that sex differences in jealousy are a legacy of humankind's past, a biological imperative that no amount of reason, no veneer of civilization, can entirely quash. In other words, genes for traits that characterized the earliest humans shape how we think, feel and act, even if we are doing that thinking, feeling and acting in cities rather than in caves. In particular, men fly into a rage over adultery because to do so is hard-wired into their genes (not to mention their jeans). The reason is that a man can never be altogether sure of paternity. If, at the dawn of humanity, a man's partner slept around, he could have wound up inadvertently supporting the child of a rival; he would also have had fewer chances of impregnating her himself. That would have given him a poor chance of transmitting his genes to the next generation. Or, put another way, only men who carried the gene that made them livid over a spouse's roaming managed to leave descendants. Says UT's Buss, ""Any man who didn't [do all he could to keep his wife from straying sexually] is not our ancestor.''

FOR A WOMAN, THE STAKES WERE DIFFERENT. IF her partner sired another's child, his infidelity could have been over in minutes. (OK, seconds.) But if he became emotionally involved with an- other woman, he might have abandoned wife No. 1. That would have made it harder for her to raise children. So women are evolutionarily programmed to become more distressed at emotional infidelity than sexual infidelity.

The journal Psychological Science recently devoted a special section to the controversy. Leading off: a study by Buss, working with colleagues from Germany and the Netherlands, in which 200 German and 207 Dutch adults were asked the standard ""which is more upsetting'' question. As usual, more men than women in both cultures said that sexual infidelity bothered them more than emotional infidelity. ""This sex difference is quite solid,'' says Buss. ""It's been replicated by our critics and in cross-cultural studies, giving exactly the results that the evolutionary theory predicts.''

Critics of the evolutionary paradigm say it is dangerous to call the jealousy gender gap a product of our genes. ""This theory holds profound implications for legal and social policy,'' says psychologist David DeSteno of Ohio State University. ""Men could get away with murder [of a sexually unfaithful spouse] by attributing it to their biology and saying they had no control over themselves.'' What's more, he argues, the theory is wrong. First, if there are genes for jealousy, they can apparently be influenced by culture. Although in every country more men than women were indeed more upset by sexual infidelity than the emotional variety, the differences between the sexes varied widely. Three times as many American men than women said that sexual treachery upset them more; only 50 percent more German men than women said that. The Dutch fell in between. So the society in which one lives can change beliefs, and thus make the gender gap larger or smaller.

More problematic for evolutionary psychology is another repeated finding. Yes, more men than women find sexual infidelity more disturbing. Something like 45 percent of men and 10 percent of women, or 30 percent of men and 8 percent of women (the numbers depend, says Buss, on how the question is worded), were more upset by the idea of sexual betrayal. But look more closely at the numbers for men. If 45, or 30, percent say that sexual betrayal disturbs them more, that means that most (55 percent, 70 percent) are not disturbed more by it. Yet evolutionary theory predicts that, even though men should not be indifferent to emotional infidelity, they should care more about the sexual kind.

Scientists who have been skeptical about the ""my genes made me think it'' theory have a different explanation for the jealousy gender gap. What triggers jealousy depends not on ancient genes, they argue, but on how you think the opposite gender connects love to sex and sex to love. Or, as psychologists Christine Harris and Nicholas Christenfeld of the University of California, San Diego, propose, ""reasonable differences between the sexes in how they interpret evidence of infidelity'' explain the gender gap. In other words, a man thinks that women have sex only when they are in love; if he learns that a woman has had sex with another man, he assumes that she loves him, too. Thus sexual infidelity means emotional infidelity as well. But men believe also that women can be emotionally intimate with another man without leaping into bed with him. A woman's emotional infidelity, then, implies nothing beyond that. By this reasoning, men see sexual betrayal as what Peter Salovey of Yale University and OSU's DeSteno call a ""double shot'' of infidelity. Sexual infidelity is therefore more threatening than mere emotional infidelity.

A woman, on the other hand, notices that men can have sex without love. Thus a man's sexual betrayal does not necessarily mean that he has fallen in love with someone else. So adultery bothers her less than it does men. But a woman also notices that men do not form emotional attachments easily. When they do, it's a real threat to the relationship. Says DeSteno, ""Whichever type of infidelity represents a double shot would bother someone more.''

Now scientists are designing experiments to show whether the mind's ability to reason, rather than genes, can explain the jealousy gender gap. The UCSD team asked 137 undergraduates the ""which distresses you more'' question. As expected, more men than women picked sexual infidelity as more upsetting. But the researchers also found differences in men's and women's beliefs. Women thought that, for men, love implies sex more often than sex implies love. And men said that, for women, sex implies love about as strongly as love implies sex. This difference in assessments of the opposite sex, argue the UCSD psychologists, explains all the gender gap in jealousy. Of course a woman is more bothered by a man's emotional infidelity than by sexual betrayal: a man in love is a man having sex, they figure, but a man having sex is not necessarily a man in love. Now, there's a shock.

OTHER EXPERIMENTS undermine as well the ""my genes made me think it'' argument. DeSteno and Salovey asked 114 undergraduates, and then 141 adults ages 17 to 70, how likely it is that someone of the opposite sex who is in love will soon be having sex, and how likely that someone of the opposite sex who is having sex is or will be in love. Anyone, man or woman, who believed that love is more likely to mean sex than sex is to mean love was more upset by emotional infidelity than by sexual infidelity. And anyone, man or woman, who believed that someone having sex is someone in love found sexual infidelity more upsetting. These data, says DeSteno, ""argue against the evolutionary interpretation. Which infidelity upsets you more seems related to [gender] only because [gender] is correlated with be-liefs about whether sex implies love and love implies sex.''

Evolutionary psychologists don't buy it. Buss points to studies showing that a woman is at greatest risk of being battered, and even murdered, by her partner when he suspects her of sexual infidelity. ""Men's sexual jealousy is an extremely powerful emotion. It makes them go berserk,'' says Buss. ""The "rational' arguments don't square with [the fact that] jealousy feels "beyond rationality.' This vague implication that culture and socialization [cause sex differences] is very old-social-science stuff that sophisticated people don't argue anymore... Sometimes I feel that I am amidst members of the Flat Earth Society.''

For all the brickbats being hurled, there is some common ground between the opposing camps. Buss and colleagues believe that jealousy, like other emotions sculpted by evolution, is ""sensitive to sociocultural conditions.'' And those who scoff at evolutionary psychology agree that, as DeSteno says, ""of course evolution plays a role in human behavior.'' The real fight centers on whether that role is paramount and direct, or whether biology is so dwarfed by culture and human reason that it adds little to our understanding of behavior. Spinning stories of how Neanderthal genes make us think and act the way we do undeniably makes for a lively parlor game. (Example: men prefer women in short skirts because they learned, millennia ago on the savanna, that women in long skirts tended to trip a lot and squash their babies.) And it is one that will be played often in 1997. If there is a lesson here, it may be this: be wary of single-bullet theories advanced so brilliantly that their dazzle gets in the way of their content.