Person:

Benenson, Joyce

Theoretical models based on primate evidence suggest that social structure determines the costs and benefits of particular aggressive strategies. In humans, males more than females interact in groups of unrelated same-sex peers, and larger group size predicts success in inter-group contests. In marked contrast, human females form isolated one-on-one relationships with fewer instrumental benefits, so social exclusion constitutes a more useful strategy. If this model is accurate, then human social exclusion should be utilized by females more than males and females should be more sensitive to its occurrence. Here we present four studies supporting this model. In Study 1, using a computerized game with fictitious opponents, we demonstrate that females are more willing than males to socially exclude a temporary ally. In Study 2, females report more actual incidents of social exclusion than males do. In Study 3, females perceive cues revealing social exclusion more rapidly than males do. Finally, in Study 4, females’ heart rate increases more than males’ in response to social exclusion. Together, results indicate that social exclusion is a strategy well-tailored to human females’ social structure.

Studies on human cooperation using economic games rarely include ecologically relevant factors. In studies on non-human primates however, both status and sex typically influence patterns of cooperation. Across primate species, high status individuals are more likely to cooperate, though this depends on the species-specific social structure of each sex. Based on human social structure, we predict that higher status males who interact more in hierarchical groups than females, will invest more than high status females in valued same-sex peers after successful cooperation. Across three studies, 187 male and 188 female participants cooperated with a (fictitious) same-sex partner who varied in competence. Participants then divided a reward between themselves and their partner. High status was induced in three different ways in each study, social influence, leadership and power. No overall sex difference in reward sharing was observed. Consistent with the hypothesis however, across all three studies, high status males invested more than high status females in cooperative partners, suggesting that high status males intuitively evaluate sharing rewards with same-sex partners as more beneficial.