Extradyadic Relationships and Jealousy

Incidence of Extradyadic Sex

Throughout history and in contemporary society, reports on the incidence of illegitimate children sired by men with women other than their wives testify to the consistent [Page 318]occurrence of extradyadic sex among males, and the fact that about 10% of children in Western societies are not sired by the legal husbands suggests that extradyadic sex is no rare phenomenon among women either. Nevertheless, there are few reliable data documenting the precise prevalence of such behavior. After reviewing 12 surveys of extramarital behavior, Thompson (1983) concluded that the probability that at least one partner in a marriage will have an extramarital relationship lies somewhere between 40% and 76%. Extradyadic sex seems to occur more often in dating and cohabiting than in marital relationships, whereas extradyadic sex seems more common in gay relationships and less common in lesbian relationships than in heterosexual relationships (Blumstein & Schwartz, 1983). Recent data indicate that there is a large cross-cultural variety in the frequency with which extradyadic sex occurs. Caraël, Cleland, Deheneffe, Ferry, and Ingham (1995) found that extramarital sex was much more prevalent in African countries than in Asian countries and that it was more prevalent among men than among women. For example, in Guinea Bissau, 38% of the men and 19% of the women had had extradyadic sex during the past year, compared to only 8% of the men and 1% of the women in Hong Kong. In the Netherlands, the comparable percentage is 5% (Van Zessen & Sandfort, 1991). It must be emphasized that these figures concern only the past year, and the lifelong incidence is likely to be considerably higher. In addition, within Western cultures there is considerable variation among various ethnic groups in the incidence of extradyadic sex. For example, more blacks than whites engage in extradyadic sex and do so more frequently (Weinberg & Williams, 1988).

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