Direct reciprocity with costly punishment: generous tit-for-tat prevails.

@article{Rand2009DirectRW,
  title={Direct reciprocity with costly punishment: generous tit-for-tat prevails.},
  author={David G. Rand and Hisashi Ohtsuki and Martin A. Nowak},
  journal={Journal of theoretical biology},
  year={2009},
  volume={256 1},
  pages={45-57}
}
The standard model for direct reciprocity is the repeated Prisoner's Dilemma, where in each round players choose between cooperation and defection. Here we extend the standard framework to include costly punishment. Now players have a choice between cooperation, defection and costly punishment. We study the set of all reactive strategies, where the behavior depends on what the other player has done in the previous round. We find all cooperative strategies that are Nash equilibria. If the cost… CONTINUE READING