Indirect reciprocity can overcome free-rider problems on costly moral assessment

Tatsuya Sasaki, Isamu Okada, Yutaka Nakai

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


Indirect reciprocity is one of the major mechanisms of the evolution of cooperation. Because constant monitoring and accurate evaluation in moral assessments tend to be costly, indirect reciprocity can be exploited by cost evaders. A recent study crucially showed that a cooperative state achieved by indirect reciprocators is easily destabilized by cost evaders in the case with no supportive mechanism. Here, we present a simple and widely applicable solution that considers pre-assessment of cost evaders. In the pre-assessment, those who fail to pay for costly assessment systems are assigned a nasty image that leads to them being rejected by discriminators. We demonstrate that considering the pre-assessment can crucially stabilize reciprocal cooperation for a broad range of indirect reciprocity models. In particular for the most leading social norms, we analyse the conditions under which a prosocial state becomes locally stable.

Original languageEnglish
Article number20160341
JournalBiology Letters
Issue number7
Publication statusPublished - 2016 Jul 1


  • Evolution of cooperation
  • Indirect reciprocity
  • Pool punishment
  • Replicator dynamics
  • Second-order free-rider
  • Social norm

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Agricultural and Biological Sciences(all)


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