Neural responses to advantageous and disadvantageous inequity

Klaus Fliessbach,Christian E Elger,Courtney B Phillipps,Bernd Weber,Armin Falk,Marieke Schnabel,Peter Trautner

doi:10.3389/fnhum.2012.00165

Abstract

In this paper we study neural responses to inequitable distributions of rewards despite equal performance. We specifically focus on differences between advantageous inequity (AI) and disadvantageous inequity (DI). AI and DI were realized in a hyperscanning functional magnetic resonance imaging (fMRI) experiment with pairs of subjects simultaneously performing a task in adjacent scanners and observing both subjects' rewards. Results showed (1) hypoactivation of the ventral striatum (VS) under DI but not under AI; (2) inequity induced activation of the right dorsolateral prefrontal cortex (DLPFC) that was stronger under DI than under AI; (3) correlations between subjective evaluations of AI evaluation and bilateral ventrolateral prefrontal and left insular activity. Our study provides neurophysiological evidence for different cognitive processes that occur when exposed to DI and AI, respectively. One possible interpretation is that any form of inequity represents a norm violation, but that important differences between AI and DI emerge from an asymmetric involvement of status concerns.

Highlights

It is a widely accepted principle of distributive justice that goods should be distributed to individuals according to their contribution, i.e., people should receive equal pay for equal work (Homans, 1961)
Pairwise comparisons showed that the disadvantageous inequity (DI) condition was associated with a significantly weaker activity compared to both conditions E (t63 = 2.76, p = 0.007) and advantageous inequity (AI) (t63 = 3.56, p < 0.001)
Our results show that: (i) ventral striatum (VS) activity is reduced for conditions of DI but not for AI. (ii) Disadvantageous inequity increases activation in the right dorsolateral prefrontal cortex (DLPFC). (iii) The evaluation of AI is related to ventrolateral prefrontal and insular regions

Summary

Introduction

It is a widely accepted principle of distributive justice that goods should be distributed to individuals according to their contribution, i.e., people should receive equal pay for equal work (equity principle) (Homans, 1961). While several studies on non-human primates have demonstrated rejections of DI, reports of animals rejecting AI (i.e., abandoning their own advantage) are scarce [for a review, see Brosnan (2009)]. These findings reveal a fundamental asymmetry between positive and negative violations of the equity principle, which cannot be explained solely in terms of inequity aversion: conceptually, inequity aversion implies an increase of dissatisfaction with increasing inequity, no matter whether this is to one’s advantage or disadvantage.

Methods

Results

Conclusion