Self-serving impulses and moral considerations often act as two opposing forces that govern our everyday behavior. But how does the brain decide which one wins?
As a step toward answering that question, Ernst Fehr of the University of Zurich and his colleagues watched as 52 volunteers played the ultimatum game, an anonymous exchange in which an individual decides whether to punish a partner's behavior at his or her own cost. In this version of the game, one player proposes how to divide 20 Swiss francs with the second player. If the responder accepts, the first player gets the money demanded and the responder gets the rest. But if the responder rejects a lopsided offer, neither gets anything. “In this game, players must overcome selfish impulses if they want to punish their partners for an unfair offer,” Fehr explains.