 The topic of polarization is anticipated in an earlier tradition of cellular automata models initiated by Robert Axelrod. The basic premise of Axelrod (1997) is that people tend to interact more with those like themselves and tend to become more like those with whom they interact. But if people come to share one another’s beliefs (or other cultural features) over time, why do we not observe complete cultural convergence? At the core of Axelrod’s model is a spatially instantiated imitative mechanism that produces cultural convergence within local groups but also results in progressive differentiation and cultural isolation between groups.