Cooperation without counting - The puzzle of friendship

Cooperative relationships, which involve the exchange of altruistic behaviors that are costly to the actor and beneficial to the recipient, are thought to be the product of kin selection or reciprocal altruism. Humans form close, enduring, cooperative relationships with nonrelatives. In these relationships, which we call friendships, both emotional and material support are exchanged. If these relationships are shaped by the adaptive logic of Tit-For-Tat reciprocal altruism, then we would expect people to keep track of benefits given to and received from friends, and for there to be contingencies between favors given now and favors received in the past. However, the social science literature suggests that Tit-for-Tat reciprocity is characteristic of relationships among casual acquaintances and strangers, not among friends. A considerable body of empirical work indicates that people value balanced reciprocity in their relationships with friends, but avoid keeping careful count of benefits given and received, and are offended when friends reciprocate immediately and directly. Thus, the dynamic of friendship does not fit the logic of models of reciprocity and presents a puzzle for evolutionary analysis.