Transforming the dilemma

Christine Taylor, Martin A. Nowak

Research output: Contribution to journalReview articlepeer-review

129 Scopus citations


How does natural selection lead to cooperation between competing individuals? The Prisoner's Dilemma captures the essence of this problem. Two players can either cooperate or defect. The payoff for mutual cooperation, R, is greater than the payoff for mutual defection, P. But a defector versus a cooperator receives the highest payoff, T, where as the cooperator obtains the lowest payoff, S. Hence, the Prisoner's Dilemma is defined by the payoff ranking T > R > P > S. In a well-mixed population, defectors always have a higher expected payoff than cooperators, and therefore natural selection favors defectors. The evolution of cooperation requires specific mechanisms. Here we discuss five mechanisms for the evolution of cooperation: direct reciprocity, indirect reciprocity, kin selection, group selection, and network reciprocity (or graph selection). Each mechanism leads to a transformation of the Prisoner's Dilemma payoff matrix. From the transformed matrices, we derive the fundamental conditions for the evolution of cooperation. The transformed matrices can be used in standard frameworks of evolutionary dynamics such as the replicator equation or stochastic processes of game dynamics in finite populations.

Original languageEnglish (US)
Pages (from-to)2281-2292
Number of pages12
Issue number10
StatePublished - Oct 2007

All Science Journal Classification (ASJC) codes

  • Genetics
  • Ecology, Evolution, Behavior and Systematics
  • General Agricultural and Biological Sciences


  • Direct and indirect reciprocity
  • Evolution of cooperation
  • Group selection
  • Kin selection
  • Network reciprocity (graph selection)
  • Prisoner's Dilemma


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