Three heads are better than one: cooperative learning brains wire together when a consensus is reached

Having a chat and then watching a movie: how social interaction synchronises our brains during co-watching

How does co-presence change our neural experience of the world? Can a conversation change how we synchronise with our partner during later events? Using fNIRS hyperscanning, we measured brain activity from 27 pairs of familiar adults simultaneously over frontal, temporal and parietal regions bilaterally, as they co-watched two different episodes of a short cartoon. In-between the two episodes, each pair engaged in a face-to-face conversation on topics unrelated to the cartoon episodes. Brain synchrony was calculated using wavelet transform coherence and computed separately for real pairs and shuffled pseudo) pairs. Findings reveal that real pairs showed increased brain synchrony over right Dorso-Lateral Pre-Frontal cortex (DLPFC) and right Superior Parietal Lobe (SPL), compared to pseudo pairs (who had never seen each other and watched the same movie at different times; uncorrected for multiple comparisons). In addition, co-watching after a conversation was associated with greater synchrony over right TPJ compared to co-watching before a conversation, and this effect was significantly higher in real pairs (who engaged in conversation with each other) compared to pseudo pairs (who had a conversation with someone else; uncorrected for multiple comparisons). The present study has shed the light on the role of social interaction in modulating brain synchrony across people not just during social interaction, but even for subsequent non-social activities. These results have implications in the growing domain of naturalistic neuroimaging and interactive neuroscience.

How self-disclosure of negative experiences shapes prosociality?

People frequently share their negative experiences and feelings with others. Little is known, however, about the social outcomes of sharing negative experiences and the underlying neural mechanisms. We addressed this dearth of knowledge by leveraging functional near-infrared spectroscopy (fNIRS) hyperscanning: while dyad participants took turns to share their own (self-disclosure group) or a stranger's (non-disclosure group) negative and neutral experiences, their respective brain activity was recorded simultaneously by fNIRS. We observed that sharing negative (relative to neutral) experiences enhanced greater mutual prosociality, emotional empathy and interpersonal neural synchronization (INS) at the left superior frontal cortex in the self-disclosure group compared to the non-disclosure group. Importantly, mediation analyses further revealed that in the self-disclosure (but not non-disclosure) group, the increased emotional empathy and INS elicited by sharing negative experiences relative to sharing neutral experiences promoted the enhanced prosociality through increasing interpersonal liking. These results indicate that self-disclosure of negative experiences can promote prosocial behaviors via social dynamics (defined as social affective and cognitive factors, including empathy and liking) and shared neural responses. Our findings suggest that when people express negative sentiments, they incline to follow up with positive actions.

Why people engage in corrupt collaboration: an observation at the multi-brain level

Recent studies suggest that corrupt collaboration (i.e. acquiring private benefits with joint immoral acts) represents a dilemma between the honesty and reciprocity norms. In this study, we asked pairs of participants (labeled as A and B) to individually toss a coin and report their outcomes; their collective benefit could be maximized by dishonestly reporting (a corrupt behavior). As expected, the likelihood of corrupt behavior was high; this probability was negatively correlated with player A's moral judgment ability but positively correlated with player B's empathic concern (EC). Functional near-infrared spectroscopy data revealed that the brain-to-brain synchronization in the right dorsolateral prefrontal cortex was associated with fewer corrupt behaviors, and that it mediated the relationship between player A's moral judgment ability and corrupt collaboration. Meanwhile, the right temporal-parietal junction synchronization was associated with more corrupt behaviors, and that it mediated the relationship between player B's EC and corrupt collaboration. The roles of these 2 regions are interpreted according to the influence of the honesty and reciprocity norms on corrupt collaboration. In our opinion, these findings provide insight into the underlying mechanisms and modulating factors of corrupt collaboration.

Letting leaders spontaneously emerge yields better creative outcomes and higher leader-follower interbrain synchrony during creative group communication

This study aimed to investigate how the ways leaders arise (appointed vs. emergent) affect the leader-follower interaction during creative group communication. Hyperscanning technique was adopted to reveal the underlying interpersonal neural correlates using functional near-infrared spectroscopy. Participants were assigned into 3-person groups to complete a creative problem-solving task. These groups were randomly split into conditions of appointed (condition A) and emergent (condition E) leaders. Creative group outcomes were better in condition E, accompanied by more frequent perspective-taking behaviors between leaders and followers. The interpersonal brain synchronization (IBS) increment for leader-follower pairs was significantly higher at the right angular gyrus (rAG), between the rAG and the right supramarginal gyrus (rSMG), and between the right middle temporal gyrus and the right motor cortex in condition E and positively correlated with perspective-taking behaviors between leaders and followers. The graph-based analysis showed higher nodal betweenness of the rAG and the rSMG in condition E. These results indicated the neural coupling of brain regions involved in mentalizing, semantic processing and motor imagery may underlie the dynamic information transmission between leaders and followers during creative group communication.

Group polarization calls for group-level brain communication

Group of people shows the shift towards extreme of decision-making as opposed to individuals. Previous studies have revealed two directions of group polarization, i.e., risky shift and cautious shift, but how group of brains drive these shifts remains unknown. In the current study, we arranged risk advantage and disadvantage situations to elicit group polarization of risky shift and cautious shift respectively, and examined the averaged inter-brain synchronization (ABS) among participant triads during group decision making versus individual decision making. The elicited group polarizations were accompanied by the enhanced ABS at bilateral prefrontal areas and left temporoparietal junction (TPJ). Specifically, the TPJ ABS was equivalent in risky shift and cautious shift, and based on machine learning analyses, could predict the extent of group polarization; for two shifts, it negatively correlated with negative emotion. However, the right prefrontal ABS was stronger in risky shift than in cautious shift, and the same area showed the larger brain deactivation in former shift, indicating weaker executive control. For the left prefrontal ABS, only the equivalent ABS was found for two shifts. In sum, group polarization of risky shift and cautious shift calls for inter-brain communication at the group level, and the former shift is with deactivation and more brain synchronization. Our study suggests emotional and cognitive adjustment in decision making of the group compared with individuals.