Neurocomputational evidence that conflicting prosocial motives guide distributive justice

A fascinating perspective and analysis from Hu et al. who show that three prosocial motives (fairness, harm aversion, and rank reversal aversion) are encoded by separate neural systems, compete for representation in various brain areas processing equality and harm signals, and are integrated in the striatum, which functions as a crucial hub for translating the motives to behavior (see also the commentary by Armstrong and McKee).  

Significance

Resource allocation in human societies usually triggers discussions about fairness, but satisfactory solutions to distribution problems also involve other prosocial motives that may prescribe different actions. Here, we address how the human brain mitigates such conflicts between multiple prosocial motives (fairness, harm aversion, and rank reversal aversion) during wealth distribution. Combining a experimental paradigm with fMRI and integrated neurocomputational modeling, we show that different prosocial motives are separately represented and integrated into choices by neural activity in striatum and its interactions with different brain regions. These findings extend unidimensional economic theories of third-party social preferences, characterize biological bases for individual and contextual differences in resource distribution behavior, and have economic and political implications for the design of taxation policies.

Abstract

In the history of humanity, most conflicts within and between societies have originated from perceived inequality in resource distribution. How humans achieve and maintain distributive justice has therefore been an intensely studied issue. However, most research on the corresponding psychological processes has focused on inequality aversion and has been largely agnostic of other motives that may either align or oppose this behavioral tendency. Here we provide behavioral, computational, and neuroimaging evidence that distribution decisions are guided by three distinct motives—inequality aversion, harm aversion, and rank reversal aversion—that interact with each other and can also deter individuals from pursuing equality. At the neural level, we show that these three motives are encoded by separate neural systems, compete for representation in various brain areas processing equality and harm signals, and are integrated in the striatum, which functions as a crucial hub for translating the motives to behavior. Our findings provide a comprehensive framework for understanding the cognitive and biological processes by which multiple prosocial motives are coordinated in the brain to guide redistribution behaviors. This framework enhances our understanding of the brain mechanisms underlying equality-related behavior, suggests possible neural origins of individual differences in social preferences, and provides a new pathway to understand the cognitive and neural basis of clinical disorders with impaired social functions.