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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

Prefrontal cortices influenced by the interaction between fairness and stake size and simple effects of the interaction effects in (A) all the proposal conditions and (B) the human proposal condition. Abbreviations: IFG, inferior frontal gyrus; SFG, superior frontal gyrus. *p < 0.05, **p < 0.01, ***p < 0.001. Error bars indicate standard errors of the mean.
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Figure 4: Prefrontal cortices influenced by the interaction between fairness and stake size and simple effects of the interaction effects in (A) all the proposal conditions and (B) the human proposal condition. Abbreviations: IFG, inferior frontal gyrus; SFG, superior frontal gyrus. *p < 0.05, **p < 0.01, ***p < 0.001. Error bars indicate standard errors of the mean.

Mentions: Given that our primary goal was to test the influence of stake size on fairness, an interesting contrast was computed by the [high(unfair−fair) − low(unfair−fair)] contrast. The bilateral insula extending to the adjacent striatum and the right middle/inferior frontal gyrus (IFG) were found to show significant contrast (p < 0.05, cluster-level correction) (Table 2). No regions survived the reverse contrast. An examination of the simple effects showed that the activation in the frontal cluster during unfair proposals was significantly stronger than during fair proposals when the stake size was high [post-hoc pairwise comparison, F(1, 27) = 24.82, p < 0.001, partial η2 = 0.479], and a similar trend was found while the stake size was low but did not meet statistical significance. In addition, the activation in the frontal cluster for high monetary proposals was significantly stronger than for low monetary proposals during the unfair proposal condition [F(1, 27) = 19.33, p < 0.001, partial η2 = 0.417] (Figure 4A). When we separated the human from the computer condition to examine the interaction of stake size and fairness, a similar pattern of interaction but with smaller clusters within those regions was found in the human condition (Table 2 and Figure 4B). No regions were influenced by the interaction between stake size and fairness in the computer condition (p < 0.05, cluster-level correction).


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)

Prefrontal cortices influenced by the interaction between fairness and stake size and simple effects of the interaction effects in (A) all the proposal conditions and (B) the human proposal condition. Abbreviations: IFG, inferior frontal gyrus; SFG, superior frontal gyrus. *p < 0.05, **p < 0.01, ***p < 0.001. 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 4: Prefrontal cortices influenced by the interaction between fairness and stake size and simple effects of the interaction effects in (A) all the proposal conditions and (B) the human proposal condition. Abbreviations: IFG, inferior frontal gyrus; SFG, superior frontal gyrus. *p < 0.05, **p < 0.01, ***p < 0.001. Error bars indicate standard errors of the mean.
Mentions: Given that our primary goal was to test the influence of stake size on fairness, an interesting contrast was computed by the [high(unfair−fair) − low(unfair−fair)] contrast. The bilateral insula extending to the adjacent striatum and the right middle/inferior frontal gyrus (IFG) were found to show significant contrast (p < 0.05, cluster-level correction) (Table 2). No regions survived the reverse contrast. An examination of the simple effects showed that the activation in the frontal cluster during unfair proposals was significantly stronger than during fair proposals when the stake size was high [post-hoc pairwise comparison, F(1, 27) = 24.82, p < 0.001, partial η2 = 0.479], and a similar trend was found while the stake size was low but did not meet statistical significance. In addition, the activation in the frontal cluster for high monetary proposals was significantly stronger than for low monetary proposals during the unfair proposal condition [F(1, 27) = 19.33, p < 0.001, partial η2 = 0.417] (Figure 4A). When we separated the human from the computer condition to examine the interaction of stake size and fairness, a similar pattern of interaction but with smaller clusters within those regions was found in the human condition (Table 2 and Figure 4B). No regions were influenced by the interaction between stake size and fairness in the computer condition (p < 0.05, cluster-level correction).

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