Interbrain Synchrony Mitigates the Polarizing Effect of Echo Chambers

People tend to engage with content that aligns with their preexisting attitudes, forming echo chambers that reinforce biases and may amplify polarization. Here, we investigate whether discussions within homogeneous groups drive polarization and whether interbrain synchronized activity between the executive control networks (ECNs) of group members can moderate this fueling effect of homogeneity on polarization. One hundred eighty-eight participants were randomly divided into groups of four individuals. They then engaged in a moral judgment task in which they privately rated and then discussed the appropriateness of actions taken to resolve moral dilemmas, while their brain activity was scanned using functional near-infrared spectroscopy (fNIRS). Group homogeneity was evaluated using participants' pre-discussion private ratings, while polarization was measured based on how extreme their post-discussion private ratings were compared to their pre-discussion ratings. Our results show that discussions within homogeneous, compared to heterogeneous groups, led to adopting more extreme views. Yet, critically, we found that higher interbrain synchrony between group members’ dorsolateral prefrontal cortex (DLPFC) during discussions diminishes this effect of homogeneity on polarization. We propose that Interbrain synchrony in the ECN may reflect shared cognitive flexibility that can counter harmful interpersonal mechanisms that take place within an echo chamber environment.