title: Heuristics guide the implementation of social preferences in one-shot Prisoner's Dilemma experiments.
abstract: Cooperation in one-shot anonymous interactions is a widely documented aspect of human behaviour. Here we shed light on the motivations behind this behaviour by experimentally exploring cooperation in a one-shot continuous-strategy Prisoner's Dilemma (i.e. one-shot two-player Public Goods Game). We examine the distribution of cooperation amounts, and how that distribution varies based on the benefit-to-cost ratio of cooperation (b/c). Interestingly, we find a trimodal distribution at all b/c values investigated. Increasing b/c decreases the fraction of participants engaging in zero cooperation and increases the fraction engaging in maximal cooperation, suggesting a role for efficiency concerns. However, a substantial fraction of participants consistently engage in 50% cooperation regardless of b/c. The presence of these persistent 50% cooperators is surprising, and not easily explained by standard models of social preferences. We present evidence that this behaviour is a result of social preferences guided by simple decision heuristics, rather than the rational examination of payoffs assumed by most social preference models. We also find a strong correlation between play in the Prisoner's Dilemma and in a subsequent Dictator Game, confirming previous findings suggesting a common prosocial motivation underlying altruism and cooperation.
authors.affiliation: Department of Mathematics, University of Southampton, Southampton, UK.
authors.forename: Valerio
authors.initials: V
authors.lastname: Capraro
authors.affiliation: Department of Psychology, Yale University, New Haven CT 06511 USA.
authors.forename: Jillian J
authors.initials: JJ
authors.lastname: Jordan
authors.affiliation: 1] Department of Psychology, Yale University, New Haven CT 06511 USA [2] Department of Economics, Yale University, New Haven CT 06511 USA [3] School of Management, Yale University, New Haven CT 06511 USA.
authors.forename: David G
authors.initials: DG
authors.lastname: Rand
mesh_terms: D001185:Artificial Intelligence; D005716:Game Theory; D006801:Humans; D007398:Interpersonal Relations; D009042:Motivation; D012919:Social Behavior