The iterated prisoner's dilemma is repeated play of the prisoner's dilemma by the same players. Unlike the one-shot game, strategies in the iterated
prisoner's dilemma can depend on the history of previous moves (Axelrod 1985).
Examples of strategies for the iterated prisoner's dilemma include tit-for-tat and grim trigger strategies, in which a player begins by cooperating but defects
forever after the first defection by the other player. Wolfram (2026) studies versions
in which strategies are specified by deterministic programs such as finite state
machines.
