Theories that reject the existence of altruism presume that emotional benefits serve as ulterior motives for doing good deeds. These theories argue that even in the absence of material and reputational benefits, individuals reap utility from the feelings associated with doing good. In response...

We explore the signal value of emotion and reason in human cooperation. Across four experiments utilizing dyadic prisoner dilemma games, we establish three central results. First, individuals believe that a reliance on emotion signals that one will cooperate more so than a reliance on reason....