Coalitional Support Regulates Resource Divisions in Men.

The logic of animal conflict predicts that organisms should assess cues of formidability to mitigate the costs of escalated contests. Accordingly, individual fighting ability has been shown to regulate the outcome of contests: All else equal, more formidable individuals claim a larger share of disputed resources, and less formidable individuals defer to their claims. The human ability to cooperate in groups complicates these interactions because a coalition of individuals can take resources from an individual that none of them could dominate when acting alone. We propose that the prevalence of male coalitional aggression in humans selected for psychological mechanisms that track how much coalitional support is immediately available to men when they are contesting a resource and use this information to regulate decisions about how to divide it. Specifically, men with coalitional allies present should be motivated to press their self-interest more than men who are acting alone-even if the solitary man has allies elsewhere. Experiments using economic games in a university lab setting were employed to test this coalitional support hypothesis. Across six experiments employing three different economic games (total n=496), coalitional support consistently regulated men's-but not women's-choices. These results suggest that coalitional support is an important factor regulating resource division in men. The fact that women pressed their self-interest, but did so whether allies were present versus absent, suggests that women's coalitional psychology was designed by different selection pressures than men's.