Interpersonal brain synchronization at frontopolar cortices underlies better advice-taking in groups.

We often seek advice from others outside our groups to optimize decision-making. This process may involve discerning the reliability of others, that is, whether the advice others provide is reliable enough to accept. However, little is known about how people collectively take advice from others. In this study, we recruited participant dyads (n = 35) to perform an advice-taking task, where they took advice collectively or individually from unreliable or reliable others. Interpersonal brain synchronization (IBS) was examined using a functional near-infrared spectroscopy-based hyperscanning technique. For advice from unreliable others, the dyads performed better than the individuals. The dyads demonstrated a higher learning rate for bad advice than for good advice, as indicated by the analysis of the Bayesian reinforcement learning model. Furthermore, they demonstrated enhanced IBS in the frontopolar cortex, which was positively correlated with learning rates and dyad performance. However, these findings did not apply to reliable others or individuals. This study shows that groups, compared to individuals, are better able to discern valuable advice from others, which may be associated with neural coupling between members. This suggests a cognitive-brain mechanism for group advice-taking.