Intrinsic and instrumental reciprocity: An experimental study

In the context of an indefinitely repeated veto game, we devise an experiment to distinguish between alternative explanations of generous behavior (accepting negative payoffs): altruism, intrinsic backward-looking reciprocity, and instrumental forward-looking reciprocity. Our results are broadly consistent with the hypothesis that observed sacrifices are motivated by equilibrium selfish, forward-looking reciprocal behavior although we find a more subtle way in which past kindness affects behavior.