Figure 14.12: Altruistic punishment increases cooperation In each trial of this social-dilemma game, each player was given 20 money units and could contribute any amount of that to a common pool. The money contributed was then multiplied by 1.4 and redistributed evenly among the four players. In one condition, players could punish low contributors by giving up one of their own money units to have three units taken away from the punished player. With the punishment option, cooperation increased from trial to trial. Without that option, it decreased from trial to trial. At the end of all trials, the players could exchange the money units they had accumulated for real money.
(Based on data from Fehr & Gächter, 2002.)