s4h-game-theory-prisoners-dilemma

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# Game Theory: Prisoner's Dilemma

The prisoner's dilemma is the central problem of cooperation. Its structure: each player has an individual incentive to defect regardless of what the other does, so both defect — and both end up worse than if they had cooperated. Individual rationality produces collective irrationality.

This structure appears everywhere: countries competing on subsidies both nations would be better without, companies in a price war that erodes margins for everyone, colleagues who each underinvest in shared infrastructure, advertisers who would all benefit if no one ran ads but each is tempted to run them. Recognising the structure is the first move; it tells you why the situation is hard and what the real leverage points are.

Robert Axelrod's computer tournaments (1984) produced one of the most important empirical results in social science: in *repeated* prisoners' dilemmas, Tit for Tat — cooperate first, then mirror your opponent's previous move — consistently outperformed every more complex strategy. Its winning properties: *nice* (cooperates first), *retaliatory* (immediately punishes defection), *forgiving* (returns to cooperation as soon as the opponent does), and *clear* (easy to understand and predict). The lesson: cooperation is achievable without altruism, if the game is repeated and players are patient.

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## Your Process

**Step 1: Structure verification**
Confirm the three conditions that define a prisoner's dilemma: