Sharing happy stories increases interpersonal closeness mediated by enhancing interpersonal brain synchronization

Our lives revolve around sharing stories with others. Expressing emotion (i.e., happy and sad) is an essential characteristic of sharing stories and could enhance the similarity of story comprehension across speaker-listener pairs. The Emotions as Social Information Model (EASI) suggests that emotional communication may influence interpersonal closeness, but the effect of sharing emotional (happy/sad) stories on interpersonal closeness remains poorly understood. Here, one speaker watched emotional videos and communicated the content of the videos to thirty-two 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. Meanwhile, the happy group showed higher interpersonal brain synchronization (IBS) in the prefrontal cortex (PFC) and temporal cortex (specifically TPJ) than the sad group. Moreover, such IBS mediated the relationship between the quality of sharing stories and interpersonal closeness, and happy emotion moderated this mediation model. The magnitude of IBS differentiated high interpersonal closeness from low interpersonal closeness. Exploratory analysis using support vector regression showed that the IBS could also predict the ratings of interpersonal closeness in left-out subjects. These results suggest that IBS could serve as an indicator of whether sharing emotional stories facilitate interpersonal closeness. These findings improve our understanding of sharing emotional information among individuals that guide behaviors during interpersonal interactions.