This paper investigates how the introduction of social preferences affects players' equilibrium behavior in both the one-shot and the infinitely repeated version of the Prisoner's Dilemma game. We show that fairness concerns operate as a 'substitute' for time discounting in the infinitely repeated game, as fairness helps sustain cooperation for lower discount factors. In addition, such cooperation can be supported under larger parameter values if players are informed about each others' social preferences than if they are uninformed. Finally, our results help to identify conditions under which cooperative behavior observed in recent experimental repeated games can be rationalized using time preferences alone (patience) or a combination of time and social preferences (fairness).
prisoner's dilemma repeated games inequity aversion time discounting social preferences