Jealousy and the nature of beliefs about infidelity: Tests of competing hypotheses about sex differences in the United States, Korea, and Japan

The different adaptive problems faced by men and women over evolutionary history led evolutionary psychologists to hypothesize and discover sex differences in jealousy as a function of infidelity type. An alternative hypothesis proposes that beliefs about the conditional probabilities of sexual and emotional infidelity account for these sex differences. Four studies tested these hypotheses. Study 1 tested the hypotheses in an American sample (N = 1,122) by rendering the types of infidelity mutually exclusive. Study 2 tested the hypotheses in an American sample (N = 234) by asking participants to identify which aspect of infidelity was more upsetting when both forms occurred, and by using regression to identify the unique contributions of sex and beliefs. Study 3 replicated Study 2 in a Korean sample (N = 190). Study 4 replicated Study 2 in a Japanese sample (N = 316). Across the studies, the evolutionary hypothesis, but not the belief hypothesis, accounted for sex differences in jealousy when the types of infidelity are rendered mutually exclusive; sex differences in which aspect of infidelity is more upsetting when both occur; significant variance attributable to sex, after controlling for beliefs; sex‐differentiated patterns of beliefs; and the cross‐cultural prevalence of all these sex differences.