Edited by Aldo Rustichini, University of Minnesota, Minneapolis, MN, and accepted by the Editorial Board September 3, 2014 (received for review August 4, 2014)
People’s preferences for income distribution fundamentally affect their behavior and contribute to shaping important social and political institutions. The study of such preferences has become a major topic in behavioral research in social psychology and economics. Despite the large literature studying preferences for income distribution, there is no direct neuronal evidence of how the brain responds to income distributions when people have made different contributions in terms of work effort. The present paper reports from, to our knowledge, the first neuroimaging study designed to examine how the brain responds to the distribution of income in such situations. As such, to our knowledge it is also the first study to examine the neuronal basis for equity theory.
The present paper reports results from, to our knowledge, the first study designed to examine the neuronal responses to income inequality in situations in which individuals have made different contributions in terms of work effort. We conducted an experiment that included a prescanning phase in which the participants earned money by working, and a neuronal scanning phase in which we examined how the brain responded when the participants evaluated different distributions of their earnings. We provide causal evidence for the relative contribution of work effort being crucial for understanding the hemodynamic response in the brain to inequality. We found a significant hemodynamic response in the striatum to deviations from the distribution of income that was proportional to work effort, but found no effect of deviations from the equal distribution of income. We also observed a striking correlation between the hemodynamic response in the striatum and the self-reported evaluation of the income distributions. Our results provide, to our knowledge, the first set of neuronal evidence for equity theory and suggest that people distinguish between fair and unfair inequalities.
Author contributions: A.W.C., T.E., K.H., K.S., E.Ø.S., and B.T. designed research; T.E., K.H., and K.S. performed research; A.W.C., T.E., K.H., K.S., E.Ø.S., and B.T. analyzed data; and A.W.C., T.E., K.H., K.S., E.Ø.S., and B.T. wrote the paper. The authors are listed in alphabetical order.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. A.R. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1414602111/-/DCSupplemental.
Freely available online through the PNAS open access option.
