## Repeated prisoner's dilemma

Instructions

You and a randomly chosen co-player for several rounds of the prisoner?s dilemma game. After each round a dice is thrown: if it shows 6, the game is stopped. Otherwise, you will play another round with the same co-player.
In every round, each can opt either for cooperation or defection. If both choose to cooperate, both get 3 points each. If you both choose to defect, you get 1 point each. If you choose defect and the other cooperate, you receive 5 points and your co-player nothing. Conversely, if you cooperate and the other defects, you receive nothing and the co-player gets 5 points.
Evaluations Number of players: 22 (11 games)
Time evolution of mean payoff and frequencies of R, S, T and P:
Notes
• Three games with persistent mutual cooperation.
• Two games where a unilateral defect occurred in the last round.
• The overall frequency of cooperate and defect is 75% to 25%.
• The repetitions increase cooperation from 50% to 75%.
Comments Most players learn during the game to defect. Thereby their payoff decreases. If the game extends further, many learn to cooperate, however.
Written by Christoph Hauert