Two experiments tested the idea that economic transactions among friends are influenced by a norm of generosity. Whereas a fairness norm ought to promote agreement in offers between buyers and sellers, a generosity norm should promote altruistic disagreements caused by sellers offering lower...

The authors introduce a new team game, the intergroup chicken game, to model intergroup conflicts involving bilateral threats (e.g., military conflicts, industrial disputes). The group that wins the game is the one that competes while the other group yields, and the benefits associated with...