Friday, September 11, 2015

The excuse principle can maintain cooperation through forgivable defection in the Prisoner's Dilemma game

 2013 Jul 17;280(1766):20131475. doi: 10.1098/rspb.2013.1475. Print 2013 Sep 7.

The excuse principle can maintain cooperation through forgivable defection in the Prisoner's Dilemma game.

Author information

  • 1Institute of Ecology and Earth Sciences, University of Tartu, , 51014 Tartu, Estonia. indrikis.krams@ut.ee

Abstract

Reciprocal altruism describes a situation in which an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, but there is an ultimate fitness benefit based on an expectation that the other organism will act in a similar manner at a later time. It creates the obvious dilemma in which there is always a short-term benefit to cheating, therefore cooperating individuals must avoid being exploited by non-cooperating cheaters. This is achieved by following various decision rules, usually variants of the tit-for-tat (TFT) strategy. The strength of TFT, however, is also its weakness-mistakes in implementation or interpretation of moves, or the inability to cooperate, lead to a permanent breakdown in cooperation. We show that pied flycatchers (Ficedula hypoleuca) use a TFT with an embedded 'excuse principle' to forgive the neighbours that were perceived as unable to cooperate during mobbing of predators. The excuse principle dramatically increases the stability of TFT-like behavioural strategies within the Prisoner's Dilemma game.

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