APPENDIX 1 On Non-zero-sumness [SNIP] - Nonzero: The Logic of Human Destiny, By Robert Wright

On Non-zero-sumness
[SNIP]

(...)The seminal exercise in computer-simulated evolution is described in Robert Axelrod's classic book The Evolution of Cooperation. It involved that most famous of non-zero-sum games, the prisoner's dilemma.


Actually, the fame is in some ways unfortunate, because the prisoner's dilemma has a couple of quirks that impede intuitive comprehension. For one thing, in this game the object is to get the lowest score, since the score represents how many years each player has to spend in prison. The second counterintuitive feature is that in this game to "cheat" is to tell the truth and to "cooperate" is to not tell the truth. But, for better or worse, the prisoner's dilemma is the textbook non-zero-sum game, so we'll here explore it by way of showing how, with the help of game theory, evolution can be simulated on a computer.


In the prisoner's dilemma, two partners in crime are being interrogated separately. The state lacks the evidence to convict them of the crime they committed but does have enough evidence to convict both on a lesser charge bringing, say, a one-year prison term for each. The prosecutor wants conviction on the more serious charge, and pressures each man individually to confess and implicate the other. She says: "If you confess but your partner doesn't, I'll let you off free and use your testimony to lock him up for ten years. And if you don't confess, yet your partner does, you go to prison for ten years. If you confess and your partner does too, I'll put you both away, but only for three years." The question is: Will the two prisoners cooperate with each other, both refusing to confess? Or will one or both of them "defect" ("cheat")?

(...)

[see: APPENDIX 1 for more, including Prisoner's Dilemma Chart ]

An excerpt from Nonzero: The Logic of Human Destiny, By Robert Wright, published by Pantheon Books. Copyright 2000 by Robert Wright. www.nonzero.org