Sunday, April 13, 2008

Psychology: Hurting oneself to hurt others not a useful social strategy ... duh!

Anna Dreber, David G Rand, Drew Fudenberg, and Martin A Nowak of the Program for Evolutionary Dynamics, Department of Economics, Stockholm School of Economics in Sweden, have published a study in Nature that shows that "Winners don't punish." They studied "costly punishment" - hurting oneself to also hurt someone else. (For example, suppose you and I are friends, reader, and we get a twofer bargain on theatre tickets. I'm mad at you, so I decide to fix you by losing the tickets, with the result that neither of us can see the play.)

The researchers found that while costly punishment increased cooperation in a group, the total payoff for the group was less. (In my example, you will pay attention thereafter when I imply that I am mad about something. But we will both lead a duller, more resentful life.)

They conclude, "This suggests that costly punishment behaviour is maladaptive in cooperation games and might have evolved for other reasons."

But how do we know that costly punishment "evolved" at all? The key weakness of evolutionary models of human behaviour is that they assume that no human being actually thinks independently in the present day. That is, the evolutionist is looking for genes or brain circuits that compel people to behave in certain ways, inherited from Pleistocene ancestors. Presumably, none of us forms judgements - wisely or unwisely - from observing our own situation.

The next step for the evolutionary psychologist is typically an unfalsifiable just-so story about how costly punishment helped our cave-dwelling ancestors - even though it has been, from time immemorial, a reliable way of losing friends and alienating people. (If I pulled the stunt described above, I bet you wouldn't agree to share the cost of theatre tickets with me again, whether or not it was a bargain.)

Anyway, here's the abstract and citation: Nature. 2008 Mar 20;452 (7185):348-51 18354481
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.

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