One of my favorite blogs, Evolved Primate, talks about how sex differences affect cooperative behavior in a prisoners’ dilemma setting:
One of the more surprising findings in these studies has been the conspicuous absence of sex related differences in cooperative behavior, as in most of the conducted experiments to date – and certainly for all results taken together – men and women seem to exhibit virtually identical rates of cooperation. This is surprising, not only because it runs counter to stereotypical clichés (intentional) about sex and gender roles, but also because it appears to conflict with competing theories in evolutionary psychology which support the notion that women and men should exhibit different behavior when it comes to cooperation.
However, results differ when they are being watched:
All of the participants were first randomly assigned to groups of 20 people, and then they played prisoner’s dilemma games against each other and against members of the other groups. In each of the experimental games, the two interacting players were watched by one of the respective groups. That is, one player was watched by his or her own group (in-group), while the other was watched by the opposing players group (out-group).
By further separating between exclusively male, exclusively female, and mixed groups in this experiment, the researchers were then able to produce a rich data set on the differential behavior of men and women in this prisoner’s dilemma with an audience. The results are summarized as follows:
Overall men and women are again found to exhibit similar levels of cooperativeness. However, the tendency to cooperate in this new design is crucially dependent on who is watching. Men cooperate less when being watched by their own group, than when being watched by the opponent’s group. Women display the opposite pattern; they cooperate when their peers are watching, but not when only members of an “out-group” are watching. The rate of cooperation when peers are watching is higher for women than it is for men, although both exhibit comparable rates of cooperation when being watched by an out-group audience. The lack of an overall gender difference in cooperativeness therefore appears to be a result of the differing responses to who is watching, and the fact that these responses run in opposite directions for men and women.
In summary, the results support the hypothesis of qualitatively different responses to social dilemmas between men and women. From an evolutionary perspective it may be argued that
“while both males and females wish to gain the approval of their in-group members, the actions that are socially desirable differ across gender. Males wish to signal that they are formidable, while females wish to signal that they are cooperative.”