How to make cooperation the optimizing strategy in a two‐person game

This paper demonstrates the existence of a partial tit‐for‐tat (matching) strategy which, when used by one player in an iterated “Prisoner's Dilemma” game, will induce a response of pure cooperation in the other player if that player behaves optimally. The minimum matching frequency of such a strategy is shown to be monotonically related to the Rapoport‐Chammah “Cooperation Index.”