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Persistent cooperation and gender differences in repeated Prisoner's Dilemma games: Some things never change
Andrew M Colman1, Briony D Pulford1, Eva M Krockow1
1Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester LE1 7RH, UK.
Acta Psychologica
|May 5, 2018
Summary
In repeated Prisoner's Dilemma games, cooperation does not decline over many rounds, contrary to common belief. A significant gender difference in cooperation rates was also observed, with men cooperating more than women.
Area of Science:
- Behavioral Economics
- Game Theory
- Social Psychology
Background:
- The finite-horizon repeated Prisoner's Dilemma theoretically predicts universal defection due to backward induction.
- Previous research suggests cooperation declines over repeated interactions, but evidence is mixed, with some studies showing recovery.
- A notable gender difference in cooperation rates was reported in early experiments.
Purpose of the Study:
- To investigate cooperation dynamics in long-term repeated Prisoner's Dilemma games.
- To test the hypothesis of declining cooperation over extended repetitions.
- To replicate and examine the reported gender differences in cooperative behavior.
Main Methods:
- Conceptual replication of the Rapoport and Chammah experiment using computerized Prisoner's Dilemma simulations.
- Repeated the game over 300 rounds with continuous play.
- Analyzed cooperation rates and identified gender-based differences.
Main Results:
- Cooperation remained stable throughout the 300 rounds, with no general decline observed.
- A significant gender difference was confirmed: men cooperated substantially more than women.
- Endgame effects were noted, with cooperation decreasing only in the final rounds.
Conclusions:
- The assumption of declining cooperation in repeated Prisoner's Dilemma is not supported by this study.
- The observed gender difference in cooperation is robust and warrants further investigation.
- Computerized simulations provide a reliable method for studying long-term game theory dynamics.