We develop awareness-dependent subjective expected utility by taking unawareness structures introduced in Heifetz et al. (J Econ Theory 130:78–94, <CitationRef CitationID="CR15">2006</CitationRef>; Games Econ Behav 62:304–324, <CitationRef CitationID="CR16">2008</CitationRef>; Unawareness, beliefs, and speculative trade. University of California, Davis, <CitationRef CitationID="CR17">2011a</CitationRef>) as primitives in...</citationref></citationref></citationref>

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...