Sharing Happy Stories Increases Interpersonal Closeness: Interpersonal Brain Synchronization as a Neural Indicator.

Our lives revolve around sharing emotional stories (i.e., happy and sad stories) with other people. Such emotional communication enhances the similarity of story comprehension and neural across speaker-listener pairs. The Social Information Model (EASI) suggests that such emotional communication may influence interpersonal closeness. However, few studies have examined speaker-listener interpersonal brain synchronization during emotional communication and whether it is associated with meaningful aspects of the speaker-listener interpersonal relationship. Here, one speaker watched emotional videos and communicated the content of the videos to thirty-two people as listeners (happy/sad/neutral group). Both speaker and listeners’ neural activities were recorded using EEG. After listening, we assessed the interpersonal closeness between the speaker and listeners. Compared to the sad group, sharing happy stories showed a better recall quality and a higher rating of interpersonal closeness. The happy group showed higher IBS in the frontal cortex and left temporoparietal cortex than the sad group. The relationship between frontal IBS and interpersonal closeness was moderated by sharing happy/sad stories. Exploratory analysis using support vector regression showed that the IBS could also predict the ratings of interpersonal closeness. These results suggest that frontal IBS could serve as an indicator of whether sharing emotional stories facilitate interpersonal closeness. These findings improve our understanding of emotional communication among individuals that guides behaviors during interpersonal interactions. Significance Statement Despite extensive research on interpersonal communication, little is known about emotional communication (happy/sad) between speaker and listener and whether these two types of emotional communication involve differential neurocognitive mechanisms from a brain-to-brain perspective. We address these questions from the perspective of the brain-to-brain approach and suggest that these two types of emotional communication are associated with differential interpersonal brain synchronization, in particular, subserved by the prefrontal region. Our findings shed light on the effect of sharing emotional (happy/sad) stories on interpersonal closeness and suggest that frontal IBS could serve as an indicator of whether sharing emotional (happy/sad) stories facilitate interpersonal closeness.