Gross Jörg, Götz Martin, Reher Katharina, Toscano Filippo
Department of Psychology, Social and Economic Psychology, University of Zurich, Zurich, Switzerland.
Commun Psychol. 2025 Jan 25;3(1):10. doi: 10.1038/s44271-025-00192-y.
Group cooperation is a cornerstone of human society, enabling achievements that surpass individual capabilities. However, groups also define and restrict who benefits from cooperative actions and who does not, raising the question of how to foster cooperation across group boundaries. This study investigates the impact of voluntary mobility across group boundaries on intergroup cooperation. Participants, organized into two groups, decided whether to create benefits for themselves, group members, or everyone. In each round, they were paired with another participant and could reward the other's actions during an 'enforcement stage', allowing for indirect reciprocity. In line with our preregistered hypothesis, when participants interacted only with in-group members, indirect reciprocity enforced group cooperation, while intergroup cooperation declined. Conversely, higher intergroup cooperation emerged when participants were forced to interact solely with out-group members. Crucially, in the free-mobility treatment - where participants could choose whether to meet an in-group or an out-group member in the enforcement stage - intergroup cooperation was significantly higher than when participants were forced to interact only with in-group members, even though most participants endogenously chose to interact with in-group members. A few 'mobile individuals' were sufficient to enforce intergroup cooperation by selectively choosing out-group members, enabling indirect reciprocity to transcend group boundaries. These findings highlight the importance of free intergroup mobility for overcoming the limitations of group cooperation.
群体合作是人类社会的基石，能带来超越个人能力的成就。然而，群体也界定并限制了谁能从合作行动中受益，谁不能受益，这就引出了如何促进跨群体边界合作的问题。本研究调查了跨群体边界的自愿流动对群体间合作的影响。参与者被分成两组，他们要决定是为自己、小组成员还是所有人创造利益。在每一轮中，他们与另一名参与者配对，并可以在“执行阶段”奖励对方的行为，从而实现间接互惠。与我们预先注册的假设一致，当参与者仅与组内成员互动时，间接互惠促进了群体合作，而群体间合作则下降。相反，当参与者被迫仅与组外成员互动时，群体间合作出现得更多。至关重要的是，在自由流动处理中——参与者可以选择在执行阶段与组内成员还是组外成员见面——群体间合作显著高于参与者被迫仅与组内成员互动时，尽管大多数参与者内生地选择与组内成员互动。少数“流动个体”通过有选择地选择组外成员来促进群体间合作，使间接互惠能够跨越群体边界。这些发现凸显了群体间自由流动对于克服群体合作局限性的重要性。
