Two suspects, held apart, are offered the same deal — will either one keep quiet?
Two suspects are arrested and questioned in separate rooms, unable to communicate. Each is offered the same deal: betray your partner and, if they stay silent, you go free while they get 10 years; if you both betray each other, you each get 5 years; if you both stay silent, you each get just 1 year on a lesser charge. Each must decide without knowing the other's choice. What should a purely self-interested suspect do?
Reveal the answer
Betraying is the dominant strategy for each individual — no matter what your partner does, you personally fare better by betraying — yet if both reason this way, they land in mutual betrayal (5 years each), worse for both than if they'd stayed silent (1 year each). Devised as a game by Merrill Flood and Melvin Dresher at RAND in 1950 and later cast as a prison scenario by Albert W. Tucker, it remains the classic illustration of individual rationality undermining collective outcomes.