When Democratic Choice Meets Identity: Cooperation in a Public Goods Game with Third-Party Punishment

兵庫県立大学 国際商経学部

This study investigates the interaction between democratic institutions and group identity in a social dilemma. While democratic legitimacy is known to enhance cooperation, its effectiveness in the presence of strong in-group bias remains under-explored. We conduct a laboratory experiment employing a factorial design that manipulates the monitor selection mechanism (democratically elected versus randomly assigned) and group identity (induced versus absent). Group identity is induced via the minimal group paradigm and reinforced by a group consolidation task. The main experimental stage features a repeated public goods game with a third-party punishment mechanism. In identity treatments, groups are mixed, comprising both in-group and out-group members relative to the monitor. Crucially, to isolate the effect of procedural legitimacy from discriminatory punishment, we enforce strict anonymity: monitors observe contribution levels but not the contributors' group affiliations. Our results demonstrate that the impact of democratic institutions varies significantly by the identity match between the monitor and the contributor. For out-group enforcement, elected monitors generate a significant "level effect," imposing stricter enforcement that raises baseline cooperation compared to exogenously assigned monitors. Conversely, regarding in-group enforcement, while punishment by a randomly assigned monitor typically triggers a collapse in cooperation due to betrayal aversion, elected monitors generate a "rebound effect." Although the negative reaction to punishment persists initially, election legitimacy buffers this effect, leading to a significant recovery in cooperation over time. These findings suggest that democratic legitimacy transforms punishment from a hostile act into a valid signal, enabling effective enforcement even in polarized environments.