The dynamics of beliefs in social decision-making: insights from intra- and inter-brain neural networks

Social beliefs are internalized expectations about others’ behaviors and intentions within social systems, shaping how individuals interpret, predict, and respond to interpersonal events. This study aims to examine how the dynamics of social beliefs influence neural activity and inter-brain synchrony within group interactions. To quantitatively assess relational changes, we implemented an iterated 3-player Prisoner’s Dilemma game paradigm, allowing for the observation of group-level behavioral patterns across repeated cooperation and defection scenarios. Participants were repeatedly exposed to cooperative and non-cooperative interactions, during which we observed neurophysiological responses associated with beliefs formation and change. Event-Related Potential analysis was used to assess individual cognitive responses to beliefs shifts, with P300 and N100 components reflecting sensitivity to social feedback. Additionally, intra-brain network analysis revealed changes centered around the parietal region, indicating altered social relationship representations at the individual level. At the group level, inter-brain synchrony significantly declined following beliefs changes, reflecting a disruption in shared intentionality and coordination. These findings suggest that violations of social expectations may induce cognitive instability and reduce neural synchrony in group decision-making contexts, offering new insights into the neural mechanisms underlying dynamic social cognition.