Cooperation among non-relatives evolves by state-dependent generalized reciprocity

Zoltan Barta*, John M. McNamara, Dora B. Huszar, Michael Taborsky

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

59 Citations (Scopus)


For decades, attempts to understand cooperation between non-kin have generated substantial theoretical and empirical interest in the evolutionary mechanisms of reciprocal altruism. There is growing evidence that the cognitive limitations of animals can hinder direct and indirect reciprocity because the necessary mental capacity is costly. Here, we show that cooperation can evolve by generalized reciprocity (help anyone, if helped by someone) even in large groups, if individuals base their decision to cooperate on a state variable updated by the outcome of the last interaction with an anonymous partner. We demonstrate that this alternative mechanism emerges through small evolutionary steps under a wide range of conditions. Since this state-based generalized reciprocity works without advanced cognitive abilities it may help to understand the evolution of complex social behaviour in a wide range of organisms.

Original languageEnglish
Pages (from-to)843-848
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1707
Publication statusPublished - 22 Mar 2011


  • tit for tat
  • internal state
  • anonymous partners
  • gratitude

Cite this