Wednesday, March 19, 2008

Nature Article on Prisoner's Dilemma

The latest issue of Nature has an interesting article on punishment and the Prisoner's Dilemma here. Here is the abstract:

Winners Don't Punish
By Anna Dreber et. al.

A key aspect of human behaviour is cooperation. We tend to help others even if costs are involved. We are more likely to help when the costs are small and the benefits for the other person significant. Cooperation leads to a tension between what is best for the individual and what is best for the group. A group does better if everyone cooperates, but each individual is tempted to defect. Recently there has been much interest in exploring the effect of costly punishment on human cooperation. Costly punishment means paying a cost for another individual to incur a cost. It has been suggested that costly punishment promotes cooperation even in non-repeated games and without any possibility of reputation effects. But most of our interactions are repeated and reputation is always at stake. Thus, if costly punishment is important in promoting cooperation, it must do so in a repeated setting. We have performed experiments in which, in each round of a repeated game, people choose between cooperation, defection and costly punishment. In control experiments, people could only cooperate or defect. Here we show that the option of costly punishment increases the amount of cooperation but not the average payoff of the group. Furthermore, there is a strong negative correlation between total payoff and use of costly punishment. Those people who gain the highest total payoff tend not to use costly punishment: winners don't punish. This suggests that costly punishment behaviour is maladaptive in cooperation games and might have evolved for other reasons.

I always knew that Peter Kropotkin was ahead of his time! Maybe these empirical studies will motivate political theorists to revive Kropotkin's ideas and insights. If I had more time that would be a project I myself would be interested in pursuing. But alas, time is becoming more and more of a scarce commodity. So little time, so many things to ponder!