Abstract
Empirical evidence indicates that people are inequity averse. However, it is unclear whether and how suffering unfairness impacts subsequent behavior. We investigated the consequences of unfair treatment in subsequent interactions with new interaction partners and the associated neural mechanisms. Participants were experimentally manipulated to experience fair or unfair treatment in the ultimatum game (UG), and subsequently, they were given the opportunity to retaliate in the dictator game (DG) in their interactions with players who had not played a role in the previous fair or unfair treatment. The results showed that participants dictated less money to unrelated partners after frequently receiving unfair offers in the previous UG (vs. frequently receiving fair offers in the previous UG), but only when they were first exposed to unfair UG/DG. Stronger activation in the right dorsal anterior insula was found during receiving unfair offers and during the subsequent offer-considering phase. The regional homogeneity (ReHo), a measure of the local synchronization of neighboring voxels in resting-state brain activity, in the left ventral anterior insula and left superior temporal pole was positively correlated with the behavior change. These findings suggest that unfair treatment may encourage a spread of unfairness, and that the anterior insula may be not only engaged in signaling social norm violations, but also recruited in guiding subsequent adaptive behaviors.
Highlights
Humans are unique among all species in the extent to which they enforce social norms through the strategy of “an eye for an eye, a tooth for a tooth.” Fairness norms, in particular, are enforced by reciprocally fair behaviors
For the remaining 27 participants, a two by five by two mixed design repeated-measure ANOVAs of the rejection rate revealed a main effect of block, with higher rejection rate in fair
The goal of the present study was to examine the consequences of unfair treatment in subsequent interactions with new interaction partners and the associated neural mechanisms
Summary
Humans are unique among all species in the extent to which they enforce social norms through the strategy of “an eye for an eye, a tooth for a tooth.” Fairness norms, in particular, are enforced by reciprocally fair behaviors. Neuroscience studies using the UG showed that unfair offers were associated with increased activity in the anterior insula (Sanfey et al, 2003; Tabibnia et al, 2008) and that rejections of unfair offers were associated with reward-related brain regions such as the dorsal striatum (Osumi et al, 2010; Crockett et al, 2013; Wu et al, 2014). There is important work that examines the neural substrates of inequity aversion, such as the effects of emotion (Hollmann et al, 2011; Kirk et al, 2011; Harle et al, 2012; Crockett et al, 2013; Grecucci et al, 2013), intentionality (Guroglu et al, 2010), decisions for the self or on behalf of third parties (Civai et al, 2012; Corradi-Dell’acqua et al, 2013), competing with peers (Halko et al, 2009), social status (Hu et al, 2014), and age (Harle and Sanfey, 2012; Bailey et al, 2013), the consequences of unfair treatment aside from the rejection of unfair offers remain largely unknown
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