Transcranial stimulation over the right temporoparietal junction decreases outcome bias

Outcome bias is the phenomenon that people often evaluate a decision more favorably if it leads to a good outcome than if it leads to a bad outcome. Although outcome bias is ubiquitous in decision evaluation, its neural mechanism remain unknown. We use transcranial direct current stimulation (tDCS) to stimulate the right temporoparietal junction (rTPJ), a cortical region associated with intention inference, to investigate the role of the rTPJ in outcome bias. We find that anodal stimulation over the rTPJ reduces outcome bias, regardless of whether the evaluators are independent third parties or non-independent second parties. This anodal stimulation effect is driven by making participants more concerned about decision intentions. Our findings provide the causal evidence for the role of the rTPJ in outcome bias and thus shed light on the neural mechanism underlying outcome bias.