Before revision:  In this study, punishment/reward is implemented by asking participants whether they want to pay a cost to decrease/increase the payoff of a defector/cooperator . Study 2 (N=253) extends Study 1 to a different method of punishing/rewarding ;
After revision:  In this study, punishment/reward . Study 2 (N=253) extends Study 1 to a different method of punishing/rewarding ;