Positive Interactions Promote Public Cooperation

Carrots Are Better Than Sticks The challenge of dealing with freeloaders—who benefit from a common good but refuse to pay their “fair share” of the costs—has often been met in theoretical and laboratory studies by sanctioning costly punishment, in which contributors pay a portion of their benefit so that freeloaders lose theirs. Rand et al. (p. 1272; see the news story by Pennisi and the cover) added a private interaction session after each round of the public goods game during which participants were allowed to reward or punish other members of their group. The outcome showed that reward was as effective as punishment in maintaining a cooperative mindset, and doing so via rewarding interactions allowed the entire group to prosper because less is lost to the costs of punishing. Reward is as good as punishment to promote cooperation, costs less, and increases the share out of resources up for grabs. The public goods game is the classic laboratory paradigm for studying collective action problems. Each participant chooses how much to contribute to a common pool that returns benefits to all participants equally. The ideal outcome occurs if everybody contributes the maximum amount, but the self-interested strategy is not to contribute anything. Most previous studies have found punishment to be more effective than reward for maintaining cooperation in public goods games. The typical design of these studies, however, represses future consequences for today’s actions. In an experimental setting, we compare public goods games followed by punishment, reward, or both in the setting of truly repeated games, in which player identities persist from round to round. We show that reward is as effective as punishment for maintaining public cooperation and leads to higher total earnings. Moreover, when both options are available, reward leads to increased contributions and payoff, whereas punishment has no effect on contributions and leads to lower payoff. We conclude that reward outperforms punishment in repeated public goods games and that human cooperation in such repeated settings is best supported by positive interactions with others.