Dopamine Modulates Egalitarian Behavior In Humans
Saez I, Zhu L, Set E, Kayser A & Hsu M. Current Biology, 2015. Abstract
Egalitarian motives form a powerful force in pro- moting prosocial behavior and enabling large-scale cooperation in the human species [1]. At the neural level, there is substantial, albeit correlational, evi- dence suggesting a link between dopamine and such behavior [2, 3]. However, important questions remain about the specific role of dopamine in setting or modulating behavioral sensitivity to prosocial con- cerns. Here, using a combination of pharmacological tools and economic games, we provide critical evi- dence for a causal involvement of dopamine in human egalitarian tendencies. Specifically, using the brain penetrant catechol-O-methyl transferase (COMT) in- hibitor tolcapone [4, 5], we investigated the causal relationship between dopaminergic mechanisms and two prosocial concerns at the core of a number of widely used economic games: (1) the extent to which individuals directly value the material payoffs of others, i.e., generosity, and (2) the extent to which they are averse to differences between their own payoffs and those of others, i.e., inequity. We found that dopaminergic augmentation via COMT inhibition increased egalitarian tendencies in participants who played an extended version of the dictator game [6]. Strikingly, computational modeling of choice behavior [7] revealed that tolcapone exerted selective effects on inequity aversion, and not on other compu- tational components such as the extent to which indi- viduals directly value the material payoffs of others. Together, these data shed light on the causal relation- ship between neurochemical systems and human prosocial behavior and have potential implications for our understanding of the complex array of social impairments accompanying neuropsychiatric disor- ders involving dopaminergic dysregulation.
[Experiment Instructions]