How we Cooperate... Perhaps

Evolutionary psychologists argue that homo sapiens’ ability to cooperate is a selected adaptation, unique to our species among the great apes. Economic theory, for the main, attempts to explain cooperative behavior as the non-cooperative equilibrium of a complex game with many stages. The innovation of behavioral economics is to include exotic arguments in preferences (for example, a sense of fairness ) but the analytical structure is still Nash (non-cooperative) equilibrium. I argue that both these approaches are unsatisfying. Instead, I propose that cooperators possess classical (non-exotic) preferences, but optimize in a cooperative (Kantian) way, and that doing so is not irrational. I distinguish between cooperative behavior and altruism, argue that altruism is unnecessary for cooperation, and indeed may not induce outcomes that are different from those that occur with cooperation, absent altruism. My approach provides microfoundations for cooperative behavior that are precisely analogous to the microfoundation that Nash equilibrium provides for non-cooperative behavior.