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Money talks: neural substrate of modulation of fairness by monetary incentives.

Zhou Y, Wang Y, Rao LL, Yang LQ, Li S - Front Behav Neurosci (2014)

Bottom Line: We found evidence for a significant modulation by the proposed amount on fairness in the right lateral prefrontal cortex (PFC) and the bilateral insular cortices.Inter-individual differences in the modulation effects in the left inferior frontal gyrus (IFG) accounted for inter-individual differences in the behavioral modulation effect as measured by the rejection rate, supporting the concept that the PFC plays a critical role in making fairness-related normative decisions in a social interaction condition.Our findings provide neural evidence for the modulation of fairness by monetary incentives as well as accounting for inter-individual differences.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Behavioral Science, Magnetic Resonance Imaging Research Center, Institute of Psychology, Chinese Academy of Sciences Beijing, China.

ABSTRACT
A unique feature of the human species is compliance with social norms, e.g., fairness, even though this normative decision means curbing self-interest. However, sometimes people prefer to pursue wealth at the expense of moral goodness. Specifically, deviations from a fairness-related normative choice have been observed in the presence of a high monetary incentive. The neural mechanism underlying this deviation from the fairness-related normative choice has yet to be determined. In order to address this issue, using functional magnetic resonance imaging we employed an ultimatum game (UG) paradigm in which fairness and a proposed monetary amount were orthogonally varied. We found evidence for a significant modulation by the proposed amount on fairness in the right lateral prefrontal cortex (PFC) and the bilateral insular cortices. Additionally, the insular subregions showed dissociable modulation patterns. Inter-individual differences in the modulation effects in the left inferior frontal gyrus (IFG) accounted for inter-individual differences in the behavioral modulation effect as measured by the rejection rate, supporting the concept that the PFC plays a critical role in making fairness-related normative decisions in a social interaction condition. Our findings provide neural evidence for the modulation of fairness by monetary incentives as well as accounting for inter-individual differences.

No MeSH data available.


Related in: MedlinePlus

(A) Regions showing the neural correlates of inter-individual differences in the behavior modulation effect of the rejection rate in the human proposal condition. (B) Significant negative correlation was found in the left IFG between the bold signal of the [high(unfair-fair) − low(unfair-fair)] contrast and the rejection rate of the [high(unfair-fair) − low(unfair-fair)] proposals. (C) Significant interaction effect of fairness*stake size was found in the left IFG for participants who deviated from the fairness norm. Abbreviations: IFG, inferior frontal gyrus. *p < 0.05. Error bars indicate standard errors of the mean.
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Figure 6: (A) Regions showing the neural correlates of inter-individual differences in the behavior modulation effect of the rejection rate in the human proposal condition. (B) Significant negative correlation was found in the left IFG between the bold signal of the [high(unfair-fair) − low(unfair-fair)] contrast and the rejection rate of the [high(unfair-fair) − low(unfair-fair)] proposals. (C) Significant interaction effect of fairness*stake size was found in the left IFG for participants who deviated from the fairness norm. Abbreviations: IFG, inferior frontal gyrus. *p < 0.05. Error bars indicate standard errors of the mean.

Mentions: Multiple regression analysis was performed to determine the regions whose BOLD signal change, which was detected using the [high(unfair−fair) − low(unfair−fair)] contrast, varied with the modulation effect on the rejection rate. Because the pattern of the interaction between stake size and fairness in the human condition was different from that in the computer condition, as shown by the abovementioned analyses, in the main text we only showed the results obtained by separating the human proposals from the computer proposals when computing inter-individual indices (for the results obtained by combining the human proposals with those of the computer proposals, please see supplementary text and Figure S3). Significantly negative correlations were found in the left IFG (MNI coordinate = [−51, 15, 15]; p < 0.05, cluster-level correction) in the human condition (Figure 6 and Table S1), which suggests that a greater IFG signal for high(unfair–fair) vs. low(unfair–fair) stakes predicts a significant deviation from the fairness-related normative decision (i.e., a reduced behavioral rejection rate for an unfair proposal with a high stake size). No regions were found in the computer condition.


Money talks: neural substrate of modulation of fairness by monetary incentives.

Zhou Y, Wang Y, Rao LL, Yang LQ, Li S - Front Behav Neurosci (2014)

(A) Regions showing the neural correlates of inter-individual differences in the behavior modulation effect of the rejection rate in the human proposal condition. (B) Significant negative correlation was found in the left IFG between the bold signal of the [high(unfair-fair) − low(unfair-fair)] contrast and the rejection rate of the [high(unfair-fair) − low(unfair-fair)] proposals. (C) Significant interaction effect of fairness*stake size was found in the left IFG for participants who deviated from the fairness norm. Abbreviations: IFG, inferior frontal gyrus. *p < 0.05. Error bars indicate standard errors of the mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4017157&req=5

Figure 6: (A) Regions showing the neural correlates of inter-individual differences in the behavior modulation effect of the rejection rate in the human proposal condition. (B) Significant negative correlation was found in the left IFG between the bold signal of the [high(unfair-fair) − low(unfair-fair)] contrast and the rejection rate of the [high(unfair-fair) − low(unfair-fair)] proposals. (C) Significant interaction effect of fairness*stake size was found in the left IFG for participants who deviated from the fairness norm. Abbreviations: IFG, inferior frontal gyrus. *p < 0.05. Error bars indicate standard errors of the mean.
Mentions: Multiple regression analysis was performed to determine the regions whose BOLD signal change, which was detected using the [high(unfair−fair) − low(unfair−fair)] contrast, varied with the modulation effect on the rejection rate. Because the pattern of the interaction between stake size and fairness in the human condition was different from that in the computer condition, as shown by the abovementioned analyses, in the main text we only showed the results obtained by separating the human proposals from the computer proposals when computing inter-individual indices (for the results obtained by combining the human proposals with those of the computer proposals, please see supplementary text and Figure S3). Significantly negative correlations were found in the left IFG (MNI coordinate = [−51, 15, 15]; p < 0.05, cluster-level correction) in the human condition (Figure 6 and Table S1), which suggests that a greater IFG signal for high(unfair–fair) vs. low(unfair–fair) stakes predicts a significant deviation from the fairness-related normative decision (i.e., a reduced behavioral rejection rate for an unfair proposal with a high stake size). No regions were found in the computer condition.

Bottom Line: We found evidence for a significant modulation by the proposed amount on fairness in the right lateral prefrontal cortex (PFC) and the bilateral insular cortices.Inter-individual differences in the modulation effects in the left inferior frontal gyrus (IFG) accounted for inter-individual differences in the behavioral modulation effect as measured by the rejection rate, supporting the concept that the PFC plays a critical role in making fairness-related normative decisions in a social interaction condition.Our findings provide neural evidence for the modulation of fairness by monetary incentives as well as accounting for inter-individual differences.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Behavioral Science, Magnetic Resonance Imaging Research Center, Institute of Psychology, Chinese Academy of Sciences Beijing, China.

ABSTRACT
A unique feature of the human species is compliance with social norms, e.g., fairness, even though this normative decision means curbing self-interest. However, sometimes people prefer to pursue wealth at the expense of moral goodness. Specifically, deviations from a fairness-related normative choice have been observed in the presence of a high monetary incentive. The neural mechanism underlying this deviation from the fairness-related normative choice has yet to be determined. In order to address this issue, using functional magnetic resonance imaging we employed an ultimatum game (UG) paradigm in which fairness and a proposed monetary amount were orthogonally varied. We found evidence for a significant modulation by the proposed amount on fairness in the right lateral prefrontal cortex (PFC) and the bilateral insular cortices. Additionally, the insular subregions showed dissociable modulation patterns. Inter-individual differences in the modulation effects in the left inferior frontal gyrus (IFG) accounted for inter-individual differences in the behavioral modulation effect as measured by the rejection rate, supporting the concept that the PFC plays a critical role in making fairness-related normative decisions in a social interaction condition. Our findings provide neural evidence for the modulation of fairness by monetary incentives as well as accounting for inter-individual differences.

No MeSH data available.


Related in: MedlinePlus