Gender differences in cooperation with group membership

We study experimentally how males and females differ in the way same-gender peers observing their action affects their social behavior. In our experiment, people play a Prisoner's Dilemma game with a partisan audience watching the choice. Two groups participated in each session; these groups could be both all-male, both all-female, or one all-male and one all-female. Groups were separated into two rooms. Each person in the group played the game once with an audience of the same group and once with audience of the other group. Behavior is significantly affected by the interaction of gender and place: males cooperate substantially less often when observed by their peer group, while females cooperate substantially more often. We discuss a possible explanation for this pattern: Males and females wish to signal their in-group peers, but males wish to signal their formidability and females wish to signal their cooperativeness.