Social Observation Increases Functional Segregation between MPFC Subregions Predicting Prosocial Consumer Decisions

Daehyun Jung,Hackjin Kim,Sunhae Sul,Minwoo Lee

doi:10.1038/s41598-018-21449-z

Daehyun Jung, Hackjin Kim + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-21449-z

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Abstract

Although it is now well documented that observation by others can be a powerful elicitor of prosocial behaviour, the underlying neural mechanism is yet to be explored. In the present fMRI study, we replicated the previously reported observer effect in ethical consumption, in that participants were more likely to purchase social products that are sold to support people in need than non-social products when being observed by others. fMRI data revealed that the anterior cingulate cortex (ACC) and the dorsomedial prefrontal cortex (dmPFC) encoded subject-specific value parameters of purchase decisions for social and non-social products, respectively, under social observation. The ACC showed strong functional coupling with the amygdala and the anterior insula when participants in the observation condition were making purchases of social versus non-social products. Finally, ventromedial prefrontal cortex (vmPFC) activity predicted faster reaction time and increased prosocial behavior during decisions to purchase social versus non-social products, regardless of social observation. The present findings suggest that subregions of the mPFC, namely the dmPFC, ACC, and vmPFC, are hierarchically organized to encode different levels of decision values from the value of context-sensitive reputation to that of internalized prosociality.

Highlights

Consistent with the notion of altruism as a signalling strategy, abundant evidence has shown that people tend to demonstrate increased prosocial tendency when their reputation concern is made salient either by social observation or by subtle surveillance cues[6]
The present study investigated the neural mechanism of observer effects on prosocial decision-making, using a consumer decision task
The pACC showed strong functional coupling with the amygdala and the anterior insula during decisions to purchase social versus non-social products

Summary

Introduction

Consistent with the notion of altruism as a signalling strategy, abundant evidence has shown that people tend to demonstrate increased prosocial tendency when their reputation concern is made salient either by social observation or by subtle surveillance cues[6]. In the specific context of prosociality, the vmPFC seems to encode decision values for highly internalized forms of altruistic behaviors (i.e., internalized prosocial valuation) as in harm-aversion in social dilemma and moral emotions[31,32,33,34,35,36,37,38], whereas the dmPFC is involved in decisions that are strategically beneficial[22,39,40] These findings altogether suggest that the impact of reputation concern on prosocial behaviors could be subserved by systematic patterns of neural activation across differential subregions in the MPFC. We adopted a novel “ethical consumption task,” where participants were instructed to make a series of binary purchase decisions on food items at given prices (Fig. 1), and manipulated the level of reputation concern to investigate the neural mechanisms of prosocial behavior in public versus in private

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