Heuristics guide the implementation of social preferences in one-shot Prisoner's Dilemma experiments

TL;DR

This study investigates cooperation in one-shot Prisoner's Dilemma experiments, revealing the influence of heuristics and social preferences on cooperative behavior, with a focus on the distribution of cooperation levels and underlying motivations.

Contribution

It introduces evidence that social preferences are guided by simple heuristics rather than rational payoff analysis, explaining persistent 50% cooperation.

Findings

Trimodal distribution of cooperation levels across b/c ratios

Increased b/c reduces zero cooperation and boosts maximal cooperation

Persistent 50% cooperation linked to heuristics, not payoff rationality

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.