The effect of punishment on cooperation in a multilevel public goods game: compositional data analysis

When addressing collective challenges, cooperation is essential both within and across subgroups. In multilevel social dilemmas, cooperation can occur at two levels: local cooperation (within one's subgroup) and global cooperation (across subgroups). While punishment has been shown to foster local cooperation in standard, non-multilevel public goods games, its role in promoting global cooperation remains unclear. To examine cooperative behavior at both levels, the present study involves 120 participants and employs a multilevel public goods game with punishment. Participants decided how to allocate endowments among self, local, and global accounts. We tested (i) whether punishment promotes local and/or global cooperation, (ii) whether individuals punish in-group or out-group members more, and (iii) what behaviors are punished. Using compositional data analysis suitable for examining allocation ratios among multiple targets, we found that punishment promoted both local and global cooperation by primarily targeting non-cooperators. Importantly, punishment behavior toward in-group and out-group members did not differ. These findings suggest that punishment can facilitate cooperation beyond subgroup boundaries and provide a potential mechanism for sustaining collective action across groups.