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Two members of a criminal gang are arrested and imprisoned. Each prisoner is in

solitary confinement with no means of communicating with the other. The prosecutors lack sufficient evidence to convict the pair on the principal charge, but they have enough to convict both on a lesser charge. Simultaneously, the prosecutors offer each prisoner a bargain. Each prisoner is given the opportunity either to betray the other by testifying that the other committed the crime, or to cooperate with the other by remaining silent. The possible outcomes are:~~Solitary Confinement~~

The** Prisoner'Prisoner's Dilemma** is a well-studied game in game theory, where supposedly rational incentive following leads to both players stabbing each other in the back and being worse off than if they had cooperated.

The ~~"stay silent"~~"stay silent" option is generally called ~~Cooperate,~~**Cooperate**, and the ~~"betray"~~"betray" option is called ~~Defect.~~**Defect**. The only Nash Equilibrium of the ~~Prisoner'~~Prisoner's Dilemma is both players defecting, even though each would prefer the cooperate/cooperate outcome.

Notice that it's only if you treat the other player's decision as completely independent from yours, if the other player defects, then you score higher if you defect as well, whereas if the other player cooperates, you do better by defecting. Hence Nash Equilibrium to defect (at least if the game is to be played only once), and indeed, this is what classical causal decision theory says. And yet—and yet, if only somehow both players could agree to cooperate, they would both do better than if they both defected. If the players are timeless decision agents, or functional decision theory agents, they can.

A popular variant is the Iterated ~~Prisoner'~~Prisoner's Dilemma, where two agents play the ~~Prisoner'~~Prisoner's Dilemma against each other a number of times in a row. A simple and successful strategy is called Tit for Tat - cooperate on the first round, then on subsequent rounds do whatever your opponent did on the last round.

(Stanford Encyclopedia of Philosophy)~~Prisoner'~~Prisoner's dilemma

Miranda Dixon-Luinenburg v1.8.0Sep 22nd 2020 (+297/-6) copied citations and external/see also links LW2

__Prisoner's dilemma__(Stanford Encyclopedia of Philosophy)

__Game theory____Decision theory____Newcomb's problem____Counterfactual mugging____Parfit's hitchhiker____Smoking lesion____Absentminded driver____Pascal's mugging__- Coordination/Cooperation

- Drescher, Gary (2006).
*Good and Real*. Cambridge: The MIT Press. ISBN 0262042339.

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