Evolution of norms for judging social behavior

Taylor A. Kessinger, Corina E. Tarnita, Joshua B. Plotkin

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Reputations provide a powerful mechanism to sustain cooperation, as individuals cooperate with those of good social standing. But how should someone s reputation be updated as we observe their social behavior, and when will a population converge on a shared norm for judging behavior? Here, we develop a mathematical model of cooperation conditioned on reputations, for a population that is stratified into groups. Each group may subscribe to a different social norm for assessing reputations and so norms compete as individuals choose to move from one group to another. We show that a group initially comprising a minority of the population may nonetheless overtake the entire population-especially if it adopts the Stern Judging norm, which assigns a bad reputation to individuals who cooperate with those of bad standing. When individuals do not change group membership, stratifying reputation information into groups tends to destabilize cooperation, unless individuals are strongly insular and favor in-group social interactions. We discuss the implications of our results for the structure of information flow in a population and for the evolution of social norms of judgment.

Original languageEnglish (US)
Article numbere2219480120
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number24
StatePublished - 2023

All Science Journal Classification (ASJC) codes

  • General


  • Cooperation
  • Evolutionary game theory
  • Indirect reciprocity
  • Reputations
  • Social evolution


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