Dürsch, Peter; Oechssler, Joerg; Schipper, Burkhard - 2013 - Revised version
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...