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It pays to be fair

This work compares two strategies entered into the 2005 Iterated Prisoner's Dilemma Competition. Both strategies select their moves based on past experience of their opponent's. They differ in their objective: One of them aims at maximum gain. The other tries to mirror its opponent's move as closely as possible. The latter strategy is fair in that it forgoes taking advantage of the opponent's cooperation. Taking into account the Competition's scoring system, the gain from mutual defection does not outweigh the loss resulting from mutual cooperation, compared to choosing the opposite move of the opponent's. Nonetheless, the latter strategy performed significantly better than the former. This confirms that altruistic strategies tend to do better than strictly selfish ones in a one-to-one comparison with other things being equal.

Read the nonpaper (pdf)

N. B.: It should be remarked that the result of this comparison is nothing new. In fact it accounts for the large importance that the Prisoner's Dilemma has in the social sciences, as it offers an explanation of how cooperative behaviour ("fairness") may have evolved in the first place. See the books by Axelrod and Poundstone cited in the nonpaper if you are interested in the topic.

Download supplementary material (gnuzipped tar format): scripts used in the investigation and intermediate data files

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