Risk and Prisoner's Dilemma: A Reinterpretation of Coombs' Re-parameterization

Wing Tung Au, Su Lu, Hildie Leung, Paton Yam, Jane M.Y. Fung

Research output: Journal article publicationJournal articleAcademic researchpeer-review

12 Citations (Scopus)


We propose a model to measure risk in a prisoner's dilemma based on Coombs' (1973) re-parameterization of the game as an individual risk decision-making task that chooses between a gamble of cooperation and another gamble of defection. Specifically, we propose an index, r, to represent the risk associated with cooperation relative to defection. In conjunction with Rapoport's (1967) index of cooperation (K), our formulation of risk allows us to construct games that vary in risk (as indexed by r) while controlling for cooperativeness (as indexed by K). Following utility analysis that models risk seeking as a convex utility function and risk averse as a concave function, we predict that risk-seeking people cooperate more in games that the cooperation choice is more risky, whereas risk-averse people cooperate more in games that the cooperation choice is less risky. In the three studies that we varied game parameters, used different measures of risk orientation and prosocial orientation and used different experimental procedures, we found robust results supporting our predictions. Theoretical analysis of our formulation further suggests that risk and cooperativeness of a prisoner's dilemma game is not entirely independent. Games that have a higher cooperativeness index are necessarily more risky.
Original languageEnglish
Pages (from-to)476-490
Number of pages15
JournalJournal of Behavioral Decision Making
Issue number5
Publication statusPublished - 1 Dec 2012
Externally publishedYes


  • Cooperativeness index
  • Prisoner's dilemma
  • Risk
  • Social value orientation

ASJC Scopus subject areas

  • Decision Sciences(all)
  • Arts and Humanities (miscellaneous)
  • Applied Psychology
  • Sociology and Political Science
  • Strategy and Management


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