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Abstract

Within the class of memory-one strategies for the iterated Prisoner’s Dilemma,
we characterize partner strategies, competitive strategies and zero-determinant
strategies. If a player uses a partner strategy, both players can fairly share
the social optimum; but a co-player preferring an unfair solution will be penalized
by obtaining a reduced payoff. A player using a competitive strategy
never obtains less than the co-player. A player using a zero-determinant
strategy unilaterally enforces a linear relation between the two players’ payoffs.
These properties hold for every strategy used by the co-player, whether
memory-one or not.