Often groups need to meet repeatedly before a decision is reached. Hence, most individual decisions will be contingent on decisions taken previously by others. In particular, the decision to cooperate or not will depend on one’s own assessment of what constitutes a fair group outcome. Making use of a repeated $N$-person prisoner’s dilemma, we show that reciprocation towards groups opens a window of opportunity for cooperation to thrive, leading populations to engage in dynamics involving both coordination and coexistence, and characterized by cycles of cooperation and defection. Furthermore, we show that this process leads to the emergence of fairness, whose level will depend on the dilemma at stake.

• Received 26 August 2011

DOI:https://doi.org/10.1103/PhysRevLett.108.158104