Interact With Your Heart, Not With Your Head: Interpersonal Neural Dynamics During Children’s Early Speech Production

Abstract

Children learn to talk through feedback loops of social interaction that drive them towards further language development. When engaged in this social interaction, the brains of children and their caregivers become coupled. One hypothesis for the origin of this coupling is the development of a shared understanding between communication partners. If true, it stands to reason that coupling would increase within dyads where children have greater command of their language and can easily convey complex ideas. To test this hypothesis, we simultaneously recorded the brains of caregivers and their 2- to 4-year-old children (N = 55) using functional Near-Infrared Spectroscopy (fNIRS). We identified each child utterance within the session, and classified its maturity. We then analyzed relationships between children’s participation in conversation (frequency and duration of utterances) and their vocal maturity (frequency, duration, and proportion of each utterance type). We found that coupling in the prefrontal cortex (PFC) was significantly increased in response to increased child laughter. Additionally, we found that the PFC of both children and their caregivers experienced an increase in activity in the moments surrounding instances of child laughter. Furthermore, we observed that language maturity does not have an effect on coupling in the PFC. We therefore suggest that coupling in the PFC may not not arise from the development of a shared understanding between interaction partners, but from moments of positive emotion within an interaction. Our study represents the first characterization of the neural dynamics of both children and their caregivers in response to child utterances of different maturities, and points towards new directions for the determination of the behavioral correlates of brain coupling.