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) argues that this is an innate difference, arising from men's need for paternity certainty and women's need for male investment in their offspring. We suggest that the difference may instead be based on reasonable differences between 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 male has sex with another man, she is in love with that other. A,woman, thinking that men can have sex without love, should still be bother ed by sexual infidelity, but less so because it does not imply that her mate has fallen in love as well. A survey of 137 subjects confirmed that men and women do differ in the predicted direction in how much they think each form of infidelity implies the other; proposing innate emotional differences may, therefore, be gratuitous.
