Cripps et al. (2005) conjectured that in an infinitely repeated game with two equally patient players, if there is positive probability that the players could be Stackelberg types, then equilibrium behavior would resemble a war of attrition, i.e., a two-sided reputation result would hold. In...

We characterize the class of symmetric two-player games in which tit-for-tat cannot be beaten even by very sophisticated opponents in a repeated game. It turns out to be the class of exact potential games. More generally, there is a class of simple imitation rules that includes tit-for-tat but...