What concept in game theory describes a situation where players have an incentive to cheat?

The prisoner's dilemma describes a situation where players have an incentive to cheat or defect, even though mutual cooperation would benefit everyone more.

The classic setup involves two suspects questioned separately. Each can remain silent or testify against the other. In the familiar payoff structure, testifying is the better individual choice whether the other suspect stays silent or testifies, making defection a dominant strategy. Yet both players would receive a better collective outcome if they cooperated.

Merrill Flood and Melvin Dresher developed the game at RAND in 1950. Mathematician Albert W. Tucker later gave it the prison-and-interrogation story and its enduring name. John Nash helped distinguish one-shot reasoning from repeated play: in repeated relationships, trust, retaliation, and reputation can make cooperation sustainable.

A common mix-up is calling every conflict a prisoner's dilemma. The defining features are the tension between individual incentives and mutual benefit, plus a payoff structure in which defection is attractive for each player. It is not the same as a zero-sum game, where one player's gain exactly offsets another's loss.