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RESEARCH PRODUCT

Hierarchy is Detrimental for Human Cooperation

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Studies of animal behavior consistently demonstrate that the social environment impacts cooperation, yet the effect of social dynamics has been largely excluded from studies of human cooperation. Here, we introduce a novel approach inspired by nonhuman primate research to address how social hierarchies impact human cooperation. Participants competed to earn hierarchy positions and then could cooperate with another individual in the hierarchy by investing in a common effort. Cooperation was achieved if the combined investments exceeded a threshold, and the higher ranked individual distributed the spoils unless control was contested by the partner. Compared to a condition lacking hierarchy, cooperation declined in the presence of a hierarchy due to a decrease in investment by lower ranked individuals. Furthermore, hierarchy was detrimental to cooperation regardless of whether it was earned or arbitrary. These findings mirror results from nonhuman primates and demonstrate that hierarchies are detrimental to cooperation. However, these results deviate from nonhuman primate findings by demonstrating that human behavior is responsive to changing hierarchical structures and suggests partnership dynamics that may improve cooperation. This work introduces a controlled way to investigate the social influences on human behavior, and demonstrates the evolutionary continuity of human behavior with other primate species. We are indebted to Luis Quevedo for discussions about the origin of rank societies. We thank Lydia Hopper, Antonio Cabrales, Gary Charness, Arno Riedl, Jordi Brandts, and Gross Jörg for feedback on an earlier version of this manuscript. We thank the anonymous reviewers for feedback that improved this manuscript. This work was supported by the Netherlands Organisation for Scientific Research, by Universidad Carlos III de Madrid, MEC Spain (ECO2013-46550-R) and the Generalitat Valenciana (PROMETEOII/2014/054).