PSYCHOLOGICAL SCIENCE Special Section GENDER, JEALOUSY, AND REASON Christine R. Harris and Nicholas Christenfeld University of California, San Diego Abstract—Research has suggested that men are especially bothered by evidence of their partner's sexual infidelity, whereas women are troubled more by evidence of emotional infidelity. One evolutionary account {Buss, Larsen, Westen, & Semmelroth, 1992) argties that this is an innate difference, aris- ing from men's need for paternity certainty and women, s need for male investment in their offspring. We suggest that the dif- ference may instead be based on reasonable differences be- tween the sexes in how they interpret evidence of infidelity, A man, thinking that women have sex only when in love, has reason to believe that if his mate has sex with another man, she is in love with that other. A woman, thinking that tnen can have sex without love, should still be bothered by sexual infidelity, but less so because it does not imply that her tnate has fallen in love as well. A survey of 137 subjects confirmed that tnen and women do differ in the predicted direction in how much they think each form of infidelity implies the other: proposing innate emotional differences tnay, therefore, be gratuitous. Buss, Larsen, Westen, and Semmelroth (1992) have sug- gested that men and women are intrinsically different in the magnitude of their responses to sexual and emotional infidelity, as a result of differing reproductive costs over human evolu- tionary history. Women, seeking to ensure males' long-term involvement, have evolved to care about their mates falling in love with others and not to be so concerned about their mates having sex with others. Men, keen not to expend resources on other men's children, should be concerned about their women having sex with others, and not care so much about their falling in love with others. Buss et al. supported their argument with data indicating that when asked to choose whether sexual or emotional infidelity would be more bothersome, more women than men selected emotional infidelity, and more men than women selected sexual infidelity. We argue here that these re- sults can be explained without suggesting that men and women are innately different in how much they are disturbed by emo- tional and sexual infidelity. Although Buss et al. and other investigators before them (Daly & Wilson, 1983; Symons. 1979J proposed an evolutionary account for men caring about sexual infidelity and women about emotional infidelity. Buss et al. argued that "emotional infidel- ity may signal sexual infidelity and vice versa, and hence both sexes should become distressed at both forms" (p. 255). We suggest instead that men and women may be equally upset by each type of infidelity and that the crucial difference may lie in how much they think that each form of infidelity signals the other. Imagine a man returning from work one day to discover Address correspondence to Christine R. Harris, Department of Psy- chology 0109, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093; e-mail: charris@ucsd.edu. incontrovertible proof of his wife's sexual infidelity. He might well think that because women have sex only when in love, it is quite certain that she has fallen in love with this other man as well. A woman, however, finding the same evidence about her husband, might think that because men often have sex without being in love, there is no reason to assume he is in love with the other woman. The man, then, is upset by what he takes to be sexual and emotional infidelity, whereas the woman is con- cerned only about sexual infidelity. The man will be more both- ered by the sexual infidelity than is the woman because he draws a more troubling conclusion from that evidence. The man should have a stronger response to sexual infidehty even if the man and woman care equally about their spouses' actual sexual exploits. The situation should be reversed with evidence of emotional infidelity. The man, on coming across evidence of this sort, should reason that women can be in love without having sex. and so he need not assume that there is sexual infidelity as well. The woman, however, thinking that men in love are certainly having sex. will assume that both sorts of treachery have oc- curred, and be doubly bothered. Thus, emotional infidelity should especially trouble women, and sexual infidelity should especially trouble men. This pre- diction follows not from any postulated innate difference in responses to the specific infidelities, but rationally from the hypothesis that men think women have sex only when in love and women think men have sex without love. We tested this hypothesis in a survey, and also sought to replicate the original finding of Buss et al. METHOD Subjects were 137 undergraduate students (55 males and 82 females) who individually and anonymously completed a sur- vey of attitudes about relationships as part of a requirement for experimental participation. Among other questions about sex- uality and dating were three questions about sexual and emo- tional infidelity. The first was taken from Buss et al. and was included to replicate their finding; the other two were designed to measure how much men and women think each form of in- fidelity implies the other: 1) Please think of a serious romantic relationship you have had in the past, currently have, or would like to have. Imagine that you discover that your romantic partner has become interested in someone else. What would upset you more? a) Imagining your partner trying different sexual positions with that other person. b) Imagining your partner falling in love with that other person. 2) Please think of a serious romantic relationship you have had in the past, currently have, or would like to have. Imagine that you discover that your mate is engaging in sexual intercourse with someone else. How likely do you think it is that your mate is in love with this person? 364 Copyright © 19% American Psychological Society VOL. 7. NO. 6. NOVEMBER 1996