Friendships, a fundamental aspect of human social life, can be traced to the ancestral conditions under which humans evolved (Cosmides & Tooby, 1992). Men and women need friends as friendships provide many benefits such as help during difficult times, advice, and access to other friends and potential mates. Men and women select same-sexfriends similar to them on a variety of dimensions such as intelligence, physical attractiveness, status, dominance, education, age, and mate value (e.g., Buss, 1984). While same-sex friendships provide adaptive benefits, such friendships may also be destructive. The strong similarity between same-sex friends may cause friends to compete for and steal mates (Buss, 1984; Tolson & Urberg, 1993). Bythe very nature of their similarity, same-sex friends may be highly compatible with their friends' mates, may have insider information about their friends' relationships with mates, and may be aware of occasions when the relationship is weak (Bleske & Shackelford, 2001).
Opposite sex friendships represent a qualitatively different type of friendship than same-sex friendships. Bleske-Rechekand Buss (2001) suggested that humans possess evolved preferences for opposite-sex friendships that have been adaptive over the course of human evolutionary history. Their in-depth study of the initiation, selection, and dissolution of opposite-sex friendships revealed some similarity with same-sex friendships. For instance, people form opposite-sex friendships to serve needs of companionship.People value friends who are honest, intelligent, and dependable and reject friends who betray, annoy, and lie. However, there are some clear sex differences in opposite-sex friendships that do not exist in same-sex friendships. For example, men, more than women, are motivated by the potential for sex from their opposite-sex friend, report being more sexually attracted to their opposite-sex friend,prefer sexual attractiveness in an opposite-sex friend, and tend to terminate opposite-sex friendships that do not provide sex. This represents men's evolved desire for sexual variety that increases chances for survival of their genes through offspring.
The research reported in this article investigates whether promiscuity plays a role in same-sex and opposite-sex friend selection. Since same-sexfriends share strong similarity and spend time with their friends' mates or potential mates, it becomes important to select same-sex friends who will not be sexual rivals. One way to determine rivalry in a potential same-sex friend is by assessing how promiscuous the person is. Having promiscuous friends may not always be a disadvantage; promiscuous friends can introduce a person to a vibrantsocial scene and to potential mates. Disadvantages arise only when a person is in a committed relationship or when there is a threat of losing mates or potential mates to the promiscuous friend. Promiscuous women may draw a man away from his mate and could possibly lead him to route his resources away from the primary relationship, leaving women and their offspring to fend for themselves (Schmitt &Buss, 1996). In comparison, promiscuous men are less desirable to women as women typically seek long-term mates.
Overview of Study
This study was designed to weave together the themes described above. Participants read brief vignettes of hypothetical people varying in sexual behavior. There were three categories of sexual behavior: overt promiscuity, subtle promiscuity, and non-promiscuity.Overt promiscuity referred to blatant displays or suggestions of sexual behavior. Subtle promiscuity was considered to be less obvious indicators of sexual behavior, and non-promiscuity was considered to be indicators of conservative sexual behavior. Participants also completed the Sociosexual Inventory (SOI; Simpson & Gangstead, 1991). The SOI is an index of a person's promiscuous tendencies....