Excerpts from

Prisoner’s Dilemma

William Poundstone


Deadlock is the least troublesome of the four [Deadlock, Prisoner’s Dilemma, Chicken and Stag Hunt]. The game looks like this (where the worst outcome is defined to have a utility of 0):

  Cooperate Defect
Cooperate 1,1 0,3
Defect 3,0 2,2

The deadlock player quickly surmises that he should defect. As in the prisoner’s dilemma, a player does better defecting no matter what his partner does. The difference is that players actually prefer mutual defection to mutual cooperation.

Players want to defect in the hope of getting 3 points. But even if they both defect, it’s no tragedy – each gets his second-best outcome. That’s better than they could do with cooperation. Deadlock is not properly a dilemma at all. There is no reason for wavering: you should defect. Mutual defection is a Nash equilibrium.

Deadlock occurs when two parties fail to cooperate because neither really wants to – they just want the other guy to cooperate. Not all failures to come to arms control agreements are the result of prisoner’s dilemmas. It may be that neither side truly wants to disarm. Possibly that was the case with the U.S. – Soviet “moment of hope” in 1955.

William Poundstone, Prisoner’s Dilemma, Doubleday, NY 1992, p. 218.

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