How parent-child brain-to-brain synchrony can inform the study of child development.

It is well established that parent-child dyadic synchrony (e.g., mutual emotions, behaviors) can support development across cognitive and socioemotional domains. The advent of simultaneous two-brain allows further insight into dyadic . In this article, we review 16 recent studies of naturalistic, parent-child brain-to-brain synchrony, finding relations with the nature of interactions (collaborative versus competitive, parent versus stranger), proximal social cues (gaze, affect, touch, reciprocity), child-level variables (irritability, self-regulation), and environmental factors (parental stress, family cohesion, adversity). We then discuss how neural synchrony may provide a biological mechanism for refining broader theories on developmental benefits of dyadic synchrony. We also highlight critical areas for future study, including examining synchrony trajectories longitudinally, including more diverse participants and interaction contexts, and studying caregivers beyond mothers (e.g., other family members, teachers). We conclude that neural synchrony is an exciting and important window into understanding how caregiver-child dyadic synchrony supports children's social and cognitive development.