Effects of group identity on resource use in a simulated commons dilemma.

In a review of research on in-group categorization and group identity, Brewer (1979) proposed that cooperative solutions to social dilemmas, such as Hardin 's (1968) "tragedy of the commons ", may be achieved by exploiting the positive consequences arising from a common social-group identity. Three laboratory experiments were conducted to assess the effects of making salient either a superordinate (collective) or subordinate (differentiating) group identity in heterogeneous groups. In the first two experiments, naturally occurring social categories were used as a basis for group differentiation. In the third, the level of social-group identity was manipulated by varying the common fate of the group members. It was predicted that individual restraint would be most likely when a superordinate group identity was made salient and under conditions in which feedback indicated that the common resource was being depleted. Results from all three experiments provide support for this general hypothesis, indicating that cooperative responding is enhanced even when the basis for superordinate group identity is minimal.