Brain regions engaged in social credibility while integrating social information and individual information to update one’s belief about the preferable judgments.

(A) The activity in the right lateral frontopolar cortex (FPC; [x,y,z] = [42,44,19]), in the precuneus (x,y,z) = (18,−58,31), and in the bilateral inferior parietal lobule (x,y,z) = (60,−34.43) and (−54,−49,52) was greater when participants were given the high-credible judgments of the large group than those when they were given the relatively low-credible information of the small group (P < 0.05, whole-brain family-wise error [FWE] corrected at cluster level; general linear model [GLM]2). (B) Whole-brain regression analysis between brain activity and the individual differences, Δσ, represents the ratio between the credibility of social information in the large group and the credibility of social information in the small group. We found that the different activity in the bilateral FPC represented the individual differences in Δσ. That is, participants with greater activation in the FPC showed higher differences in the credibility that they assigned to the judgments of a larger group relative to those of a smaller group (P < 0.05 FWE corrected at the cluster level; GLM2). The functional MRI (fMRI) data can be found in The data underlying Fig 5B can be found in S1 Data.