Preference Evolution, Two-Speed Dynamics, and Rapid Social Change*

We present a dynamic analysis of the evolution of preferences in a strategic environment. In our model, each player’s behavior depends upon both the game’s payoffs and his idiosyncratic biases, but only the game’s payoffs determine his evolutionary success. Dynamics run at two speeds at once: while natural selection slowly reshapes the distribution of preferences, players quickly learn to behave as their preferences dictate. We establish the existence and uniqueness of the paired trajectories of society's preferences and aggregate behavior. While aggregate behavior adjusts smoothly in equilibration games, in coordination games aggregate behavior can jump discretely in an instant of evolutionary time.