Voluntary play increases cooperation in the presence of punishment: A lab in the field experiment

Problems of cooperation have often been simplified as the choice between defection and cooperation, although in many empirical situations it is also possible to walk away from the interaction. When opting out of is a feasible alternative, it is questionable whether known solutions to the problem of cooperation, such as punishment could still work, given the limited sanctioning potential it imposes on free riders. We present the results of two experiments with non-student subjects who play optional and compulsory public goods games both with and without a punishment stage. We find that the possibility of opting-out motivates cooperation. Instead, when punishment is introduced, higher cooperation emerges in the compulsory game. This key result indicates that informal solutions to public good problems might rule each other out and punishment is a robust solution only if players are not allowed to opt out of the interaction.