Whether Modulating the Activity of the Temporalparietal Junction Alters Distribution Decisions within Different Contexts: Evidence from a tDCS Study

Distinct role of the right temporoparietal junction in advantageous and disadvantageous inequity: A tDCS study

Fairness is a hallmark of humans' ability to maintain cooperative relationships with large numbers of unrelated others. It influences many aspects of daily life, from how people share their resources with partners to how policymakers shape income distribution policy. The right temporoparietal junction (rTPJ) is a hub of the mentalizing network and it has been proposed to play a key role in guiding human reciprocal behavior; however, its precise functional contribution to fair behavior in situations of advantageous and disadvantageous inequity remains unclear. The purpose of this study was to clarify the role of the rTPJ in relation to fair behavior in situations of advantageous and disadvantageous inequity by modulating the activation of the rTPJ through transcranial direct current stimulation (tDCS). Anodal tDCS at 1.5 mA over the primary visual cortex (VC) or rTPJ was performed and participants subsequently played a binary-choice version of the Dictator Game. We found that anodal tDCS over the rTPJ increased the participants' equity choices in the disadvantageous inequity situation but not in the advantageous inequity situation. The tDCS effect is moderated by sex and, in particular, the tDCS effect increases female equity choices. The results suggest that the rTPJ plays a distinct role in inequity aversion in these two types of inequity situations.

Modulating the activity of right temporo-parietal junction increases bidding behavior in lottery contests

Contest often involves bids that are higher than the Nash equilibrium, and overbidding behaviour closely relates to personal reasoning and judgement. The right temporo-parietal junction (rTPJ) plays an important role in social, cognitive and inference decision-making. In the present study, we investigated the effect of transcranial direct current stimulation (tDCS) of the rTPJ on overbidding behaviour by using a modified model-lottery contests task. Our results showed that participants that received cathodal-stimulation had significantly higher expenditure compared to participants that received anodal and sham stimulation. Cathodal-stimulation may reduce the participants' ability to infer other contestants' intention or may modulate the non-monetary utility of winning. Our data indicate that excitability of the rTPJ may contribute to overbidding behaviour.

Modulating the activity of right temporo-parietal junction by anodal tDCS enhances the agent's repayment in hold-up game

Hold-up problem is very common in non-contractible relation-specific investment transactions. And this problem can affect by trust, cooperation and altruism behavior of human beings. Recent neuroscience researches had explored a network of right temporo-parietal junction (rTPJ) involved in human cooperation and altruism behavior. The purpose of this study is to modulate the activation of rTPJ through transcranial direct current stimulation (tDCS), and to study the influence of rTPJ on investment and offer behavior in hold-up game. The results of our study showed that the anodal stimulation significantly increased participants' offer compared with the cathodal and sham stimulation. A possible explanation is that changes in rTPJ activity induced by anodal stimulation improve the accuracy of agents' mental reasoning and promote cooperation by influencing agents' offer behavior.

Causal Role of the Right Dorsolateral Prefrontal Cortex in Organizational Fairness Perception: Evidence From a Transcranial Direct Current Stimulation Study

The right dorsolateral prefrontal cortex (rDLPFC) plays an essential role in social decision-making. Although several neural imaging studies have provided evidence that the rDLPFC is correlated with fairness perception, little research has investigated the causal effect of this encephalic region on individuals’ consciousness, particularly perceptions of organizational fairness. The present study explores the causal relationship between the rDLPFC and organizational fairness perception by using brain modulation techniques. Healthy participants received transcranial direct current stimulation (tDCS) and fulfilled the modified ultimatum game (UG) in the sham-controlled experiment. Our results showed that only cathodal stimulation of the rDLPFC resulted in increasing rejection offers compared with the sham stimulation in conditions of disadvantageous inequity. No differences were found between the anodal and sham stimulation in any inequity condition. This study strengthens the main functional effects of the rDLPFC in negative emotional control in relation to organizational fairness perceptions.

Anodal tDCS Over the Right Temporoparietal Junction Lowers Overbidding in Contests

Overbidding, which means bidding over the Nash equilibrium, is commonly observed in competitive social interactions, such as a contest or auction. Recent neuroscience studies show that the right temporoparietal junction (rTPJ) is related to overbidding and associated with inferring the intentions of others during competitive interactions. The present study investigates the neural underpinnings of overbidding and how the rTPJ impacts bidding behavior by using tDCS to modulate the activation of the rTPJ. Participants completed a two-person proportional prize contest, in which overbidding was frequently observed and each participant's share of the prize was equal to the individual's expenditure divided by the aggregated expenditure. We observed a significant tDCS effect, i.e., participants' average expenditure and overbidding rate were significantly reduced in the anodal stimulation compared with the cathodal and sham stimulation. Possible explanations include that enhanced activity in the rTPJ via the anodal stimulation increased the accuracy of a participant's inference of the strategies of others, or a participant's concern for others, and thus helped the participant bid optimally. Our findings provide evidence supporting that the activation of the rTPJ in contests affects overbidding and bidding strategy, and further confirm that the rTPJ is involved in the inference of mental states in a competition context.

Stimulating the Right Temporoparietal Junction with tDCS Decreases Deception in Moral Hypocrisy and Unfairness

Self-centered and other-regarding concerns play important roles in decisions of deception. To investigate how these two motivations affect deception in fairness related moral hypocrisy, we modulated the brain activity in the right temporoparietal junction (rTPJ), the key region for decision making involved in self-centered and other-regarding concerns. After receiving brain stimulation with transcranial direct current stimulation (tDCS), participants finished a modified dictator game. In the game, they played as proposers to make allocations between themselves and recipients and had a chance to deceive by misreporting their totals for allocations. Results show that deception in moral hypocrisy was decreased after anodal stimulation than sham and cathodal stimulation, only when participants know that their reported totals (appearing fair) would be revealed to recipients rather than being unrevealed. Anodal stimulation also increased offers to recipients than cathodal stimulation regardless of the revelation of reported totals. These findings suggest that enhancing the activity of rTPJ decreased deception caused by impression management rather than self-deception in moral hypocrisy and unfairness through facilitating other-regarding concerns and weakening non-material self-centered motivations. They provide causal evidence for the role of rTPJ in both other-regarding concerns and non-material self-centered motivations, shedding light on the way to decrease moral hypocrisy.