Investigating mother–child inter‐brain synchrony in a naturalistic paradigm: A functional near infrared spectroscopy (fNIRS) hyperscanning study

Abstract Successful social interactions between mothers and children are hypothesised to play a significant role in a child's social, cognitive and language development. Earlier research has confirmed, through structured experimental paradigms, that these interactions could be underpinned by coordinated neural activity. Nevertheless, the extent of neural synchrony during real‐life, ecologically valid interactions between mothers and their children remains largely unexplored. In this study, we investigated mother–child inter‐brain synchrony using a naturalistic free‐play paradigm. We also examined the relationship between neural synchrony, verbal communication patterns and personality traits to further understand the underpinnings of brain synchrony. Twelve children aged between 3 and 5 years old and their mothers participated in this study. Neural synchrony in mother–child dyads were measured bilaterally over frontal and temporal areas using functional Near Infra‐red Spectroscopy (fNIRS) whilst the dyads were asked to play with child‐friendly toys together (interactive condition) and separately (independent condition). Communication patterns were captured via video recordings and conversational turns were coded. Compared to the independent condition, mother–child dyads showed increased neural synchrony in the interactive condition across the prefrontal cortex and temporo‐parietal junction. There was no significant relationship found between neural synchrony and turn‐taking and between neural synchrony and the personality traits of each member of the dyad. Overall, we demonstrate the feasibility of measuring inter‐brain synchrony between mothers and children in a naturalistic environment. These findings can inform future study designs to assess inter‐brain synchrony between parents and pre‐lingual children and/or children with communication needs.