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March 01, 2011


Mike Scott

Your description in #15 is not a Prisoner's Dilemma. For a proper Prisoner's Dilemma, if one caves then that one wins big and the other one loses big.

Technically, it is necessary that:

(score for defecting while other player cooperates) > (score for mutual cooperation) > (score for mutual defection) > (score for cooperating while other player defects)

and also:

(score for mutual cooperation) > (average score for scenario where one player defects and one cooperates).

Joe Buck

@Mike Scott: no, in the original Prisoner's Dilemma, if neither prisoner talks, they both get off. If one talks, that prisoner gets a reduced sentence and the other gets a severe sentence. Since the best possible payoff is to go free, the best outcome is for neither to talk, but the minimax solution is for both to cave and get the reduced sentence.

J Taylor

@Joe Buck The original prisoner's dilemma is thus:

Two suspects are arrested by the police. The police have insufficient evidence for a conviction, and, having separated the prisoners, visit each of them to offer the same deal. If one testifies for the prosecution against the other (defects) and the other remains silent (cooperates), the defector goes free and the silent accomplice receives the full 10-year sentence. If both remain silent, both prisoners are sentenced to only six months in jail for a minor charge. If each betrays the other, each receives a five-year sentence. Each prisoner must choose to betray the other or to remain silent. Each one is assured that the other would not know about the betrayal before the end of the investigation. How should the prisoners act?

(retrieved from wikipedia)

In yours, there is no incentive to talk whatsoever, so there's not really any "dilemma" to go with it.

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