Causal role of right dorsolateral prefrontal cortex for norm-guided social decision making: A meta-analysis of TMS studies.

Theoretical accounts ascribe the right dorsolateral prefrontal cortex (rDLPFC) a crucial role in social decision making, but previous studies assessing the rDLPFC's function with transcranial magnetic stimulation (TMS) provided inconsistent evidence. While some studies suggest that the rDLPFC promotes norm-guided behavior, others report the rDLPFC to implement selfish choices. To decide between these conflicting accounts, we conducted a meta-analysis of studies that investigated the impact of rDLPFC TMS on social decision making. While we observed no significant effect of rDLPFC TMS across all studies, moderator analyses revealed that the rDLPFC's role in social decision making crucially depends on the social context: in particular, we found that rDLPFC promotes norm-guided behavior predominantly when decision makers have to trade-off their interaction partners' intentions and fairness expectations against their selfish interests (reactive fairness). In contrast, there was no evidence that rDLPFC TMS affects prosocial giving (proactive fairness). Our results thus inform theoretical accounts by showing that brain stimulation over rDLPFC does not increase or decrease norm-guided behavior per se; instead, contextual factors determine the role of the rDLPFC in social interactions.

Generosity in dictator game and social value orientation predicted the type of costly punishment in ultimatum game.

The current study investigated two types of punishment (prosocial and proself punishment) in the ultimatum game (UG) and examined the impact of individuals' prosocial orientation on the costly punishment in the UG in a representative sample of Chinese undergraduate students (N = 344). The prosocial orientation was measured with individuals' performance in the dictator game (DG), social value orientation (SVO), and the personal norm of reciprocity. Prosocial and proself punishers were established with responses in advantage and disadvantage offers in the UG. Results showed that prosocial and proself punishers coexisted in the UG, and prosocial punishers were more likely to be prosocial in SVO and allocated more resources to the recipient in the DG than proself punishers, but differences in positive/negative reciprocity between prosocial and proself punishers were not found. Further regression analysis found that SVO type and generosity in the DG could predict the type of punishers in the UG, but not positive/negative reciprocity. These findings indicate that individuals rejecting unfair offers in the UG may be motivated by either prosocial motivation with strict fairness concern (prosocial punishment) or selfish motivation with maximizing self-interest concern (proself punishment). Moreover, SVO type and generosity in the DG might be effective measures to discriminate prosocial and proself punishers in the UG.