A causal role of the human left temporoparietal junction in computing social influence during goal-directed learning

The human temporoparietal junction (TPJ) is a brain area crucial for processing social information. Although brain stimulation studies have started to explore the causal function of TPJ under social contexts, few have explicitly considered bilateral TPJ as target regions. Here, leveraging non-invasive continuous theta-burst stimulation (cTBS) and hierarchical Bayesian computational modeling, we tested whether left or right TPJ (with vertex as control) is causally involved in how dissenting choices by others influence individuals choice adjustments in goal-directed learning. In our social learning paradigm, participants (N = 31) first made their private decision, and then were allowed to re-adjust their choices after observing choices of four other players. Behaviorally, we show that disruption of the left, but not the right TPJ, weakened participants choice adjustment and delayed their response speed when confronted with dissenting information from the other players. Computationally, disrupting activity in the left TPJ attenuated the degree of computing social influence during choice adjustment, whereas the extent to which how observational learning from others choices was integrated into direct learning remained intact. Together, our results provide evidence for the causal role of left TPJ in social influence during goal-directed learning and shed light on the relational function (with respect to oneself) of the TPJ in social cognition.