The Neural Basis of Social Influence in a Dictator Decision.

Zhenyu Wei,Zhiying Zhao,Yong Zheng

doi:10.3389/fpsyg.2017.02134

Abstract

Humans tend to reduce inequitable distributions. Previous neuroimaging studies have shown that inequitable decisions are related to brain regions that associated with negative emotion and signaling conflict. In the highly complex human social environment, our opinions and behaviors can be affected by social information. In current study, we used a modified dictator game to investigate the effect of social influence on making an equitable decision. We found that the choices of participants in present task was influenced by the choices of peers. However, participants’ decisions were influenced by equitable rather than inequitable group choices. fMRI results showed that brain regions that related to norm violation and social conflict were related to the inequitable social influence. The neural responses in the dorsomedial prefrontal cortex, rostral cingulate zone, and insula predicted subsequent conforming behavior in individuals. Additionally, psychophysiological interaction analysis revealed that the interconnectivity between the dorsal striatum and insula was elevated in advantageous inequity influence versus no-social influence conditions. We found decreased functional connectivity between the medial prefrontal cortex and insula, supplementary motor area, posterior cingulate gyrus and dorsal anterior cingulate cortex in the disadvantageous inequity influence versus no-social influence conditions. This suggests that a disadvantageous inequity influence may decrease the functional connectivity among brain regions that are related to reward processes. Thus, the neural mechanisms underlying social influence in an equitable decision may be similar to those implicated in social norms and reward processing.

Highlights

Previous studies have found that humans’ decision-making behaviors are sensitive to inequality considerations, and display a social preference for reducing inequity in distributions (Adams, 1965; Fehr and Schmidt, 1999; Bolton and Ockenfels, 2000; Tricomi et al, 2010)
We hypothesized that inequitable group choices would activate the brain regions that are associated with norm violations and reinforcement learning, such as the dorsomedial prefrontal cortex and the rostral cingulate zone (RCZ)
The results indicated that the main effect of social influence was significant in the insula, medial prefrontal cortex (mPFC), middle frontal gyrus (MFG), bilateral middle temporal gyrus (MTG), superior frontal gyrus (SFG), inferior frontal gyrus (IFG), inferior temporal gyrus (ITG), bilateral inferior parietal lobule (IPL), cuneus, parahippocampal gyrus, postcentral gyrus, posterior cingulate, and cingulate gyrus

Summary

Introduction

Previous studies have found that humans’ decision-making behaviors are sensitive to inequality considerations, and display a social preference for reducing inequity in distributions (Adams, 1965; Fehr and Schmidt, 1999; Bolton and Ockenfels, 2000; Tricomi et al, 2010). Using experimental games with real rewards, researchers have found that people will sacrifice benefits to themselves both when they are offered less than a recipient (disadvantageous inequity) as well as when they are offered more (advantageous inequity) (Loewenstein et al, 1989; Camerer, 2003; Fehr and Fischbacher, 2003; Dawes et al, 2007). One such game, the Dictator Game, has been used to study individuals’. Subjects were found to give 25% of the total to the recipient, which is not a rational decision (Forsythe et al, 1994; Hoffman et al, 1996)

Methods

Results

Discussion

Conclusion