Unlocking the doors of the prisoner's dilemma: Dependence, selectivity, and cooperation

Although the Prisoner's Dilemma game has been widely investigated, fell, st udies have explored what happens when the doors to the prison are unlocked. Conventional game-theoretic analysis predicts greater cooperation in ongoi ng relationships than with occasional partners This suggests that an option to exit decreases cooperation by reducing players' dependence on each othe r far help in the future. An alternative hypothesis is that cooperation inc reases with selectivity - that is, with the ability to play with a desired partner. This suggests that an exit option increases cooperation. We tested both hypotheses in laboratory experiments with human subjects, using "Trum p", a new card-game representation of a Prisoner's Dilemma. In the first ex periment, the exit option reduced dependence and increased selectivity, rel ative to a no-exit condition. We found that selectivity and dependence both increased cooperation, but for different reasons and with different player s; leaving overall cooperation rates unchanged by an option to exit. In a s econd experiment, the exit option increased selectivity but not dependence relative to a forced-suit condition, Here we observed higher cooperation wi th an option to exit, but only for subjects playing defensive strategies.