Women Tend to Defect in a Social Dilemma Game in Southwest China

Factors of influence in prisoner's dilemma task: a review of medical literature

The Prisoner's Dilemma (PD) is one of the most popular concepts amongst the scientific literature. The task is used in order to study different types of social interactions by giving participants the choice to defect or cooperate in a specific social setting/dilemma. This review focuses on the technical characteristics of the PD task as it is used in medical literature and describes how the different PD settings could influence the players' behaviour. We identify all the studies that have used the PD task in medical research with human participants and distinguish, following a heuristic approach, seven parameters that can differentiate a PD task, namely (a) the opponent parties' composition; (b) the type of the opponent as perceived by the players; (c) the interaction flow of the game; (d) the number of rounds; (e) the instructions narrative and options that are given to players; (f) the strategy and (g) the reward matrix and payoffs of the game. We describe how each parameter could influence the final outcome of the PD task and highlight the great variability concerning the settings of these parameters in medical research. Our aim is to point out the heterogeneity of such methods in the past literature and to assist future researchers with their methodology design.

Persistent cooperation and gender differences in repeated Prisoner's Dilemma games: Some things never change

In the finite-horizon repeated Prisoner's Dilemma, a compelling backward induction argument shows that rational players will defect in every round, following the uniquely optimal Nash equilibrium path. It is frequently asserted that cooperation gradually declines when a Prisoner's Dilemma is repeated multiple times by the same players, but the evidence for this is unconvincing, and a classic experiment by Rapoport and Chammah in the 1960s reported that cooperation eventually recovers if the game is repeated hundreds of times. They also reported that men paired with men cooperate almost twice as frequently as women paired with women. Our conceptual replication with Prisoner's Dilemmas repeated over 300 rounds with no breaks, using more advanced, computerized methodology, revealed no decline in cooperation, apart from endgame effects in the last few rounds, and replicated the substantial gender difference, confirming, in the UK, a puzzling finding first reported in the US in the 1960s.