Once Nice, Always Nice? Results on Factors Influencing Nice Behavior from an Iterated Prisoner's Dilemma Experiment

The reliability of human behavior in situations where cooperation is beneficial for all but is hindered by individual incentives not to cooperate is a central research question in economics and the social sciences. Little is known about how the interaction results of a subject with one partner may affect this subject's behavior when subsequently matched with a new partner. We extend this knowledge by studying the development of cooperation in a repeated prisoner's dilemma experiment. After several rounds, each subject is matched with a new partner. We analyse whether the interaction outcomes with the first partner lead subjects to change their behavior when they interact with the second partner. We focus on niceness as introduced by Axelrod and find statistically significant effects. Mutual cooperation with the first partner is positively correlated with the continuation of a nice strategy, whereas mutual defection leads subjects to give up their nice strategy.