Jealousy has been the focus of both theoretical formulation and empirical investigation (see Pines, 1992; Salovey, 1991; White & Mullen, 1989, for reviews). Although several types of envy and jealousy have been recognized, sexual jealousy has received the most attention by researchers (Cano & O'Leary, 1997; White & Mullen, 1989), and appears to be a ubiquitous experience (Mullen & Martin, 1994; Pines, 1992). In particular, several researchers have been interested in potential gender differences in the stimuli for sexual jealousy. In general, it appears that men may be more sensitive to the sexual aspects of infidelity, whereas women are more prone to focus on the emotional or relationship implications of infidelity (Buss, Larsen, Westen, & Semmelroth, 1992; Buunk, Angleitner, Oubaid, & Buss, 1996; Geary, Rumsey, Bow-Thomas, & Hoard, 1995; Symons, 1979; Wiederman & Allgeier, 1993).
Researchers have commonly taken an evolutionary perspective in attempting to explain this apparent gender difference in the stimulus for jealousy. That is, it is hypothesized that contemporary men and women possess different psychological mechanisms having to do with concern about sexual versus emotional infidelity, as each type of infidelity had different repercussions for ancestral males versus females throughout our evolutionary history (Allgeier & Wiederman, 1994; Buss, 1994; Symons, 1979; Wiederman & Allgeier, 1993). Sexual infidelity by a female might result in decreased paternity confidence for the steady male partner, as it is possible that such infidelity would result in conception and pregnancy. For women, confidence in their genetic relationship to their own offspring is not an issue, but potential diversion of resources or abandonment on the part of a wayward relationship partner was potentially of great relevance during our evolutionary history. Evolutionary theorists posit that one would expect corresponding gender differences in sexual jealousy, such that men would be more concerned about potential extradyadic sexual involvement by a steady relationship partner whereas women should be more concerned about potential extradyadic emotional involvement. Indeed, men do appear to be more suspicious than women regarding their mate's sexual fidelity (e.g., Paul & Galloway, 1994) when, in fact, men are more likely than women to have such extradyadic sexual involvement both before (Wiederman & Hurd, in press) and after (Wiederman, 1997) marriage.
Despite the prevalence of sexual jealousy and the recent theorizing and research on the topic from an evolutionary perspective, many questions regarding sexual jealousy remain. For example, does the gender of the interloper affect people's perceptions of the jealousy-inducing liaison? Specifically, do men and women differ in their reactions to a romantic partner engaging in a same-gender versus other-gender encounter outside of the primary relationship? White and Mullen (1989) raised these questions nearly a decade ago. Surprisingly, to our knowledge they have not been addressed by researchers. The objective of the current series of studies was to investigate possible effects of the gender of the interloper in young adults' perceptions of potentially jealousy-evoking situations during courtship.
Possible gender differences in reactions to a dating partner's same-gender versus other-gender sexual encounter outside the primary relationship were investigated. Despite the lack of previous findings upon which to base specific hypotheses, we expected women to be more upset over the notion of their partner engaging in a same-gender encounter compared to an other-gender encounter, whereas we hypothesized that men would display more concern over the notion of their partner engaging in sexual activity with another male compared to engaging in sexual activity with a female. From an evolutionary perspective, sex between two women …