Transcranial direct current stimulation of the rLPFC shifts normative judgments in voluntary cooperation

Normative judgment is a key capacity for human social norm compliance. Previous studies have revealed that the right lateral prefrontal cortex (rLPFC) is closely related to social norm compliance and that it has proven stimulation effects on behavior in voluntary and sanction-induced norm compliance, but not normative judgments. Nearly all these studies have been based on sanction-induced coordination cooperation, and a number of them have found that rLPFC has no effect on normative judgment with transcranial direct current stimulation (tDCS). However, no research study exists regarding the effects of the normative judgment in voluntary cooperation. In this study, we used a linear asymmetric public good game to investigate the role of normative judgment in voluntary cooperation with tDCS on rLPFC. Participants were engaged in anonymous social interactions and made decisions with real financial consequences after being randomly assigned to receive either anodal, cathodal, or sham stimulation of 15 min. Results suggest that compared with the sham group, anodal/cathodal tDCS influenced the behavior and normative judgment of participants in opposite directions. These outcomes provide a neural evidence for the rLPFC mechanism on normative judgment in voluntary cooperation.