A developmental framework of interpersonal neural synchrony.

Interpersonal neural synchrony (INS), the temporal alignment of brain activities between individuals, has been proposed as a biomarker for successful communication and smooth social interaction. Surging empirical evidence shows that INS emerges spontaneously between infants, children, and their caregivers from early on in development. Yet, little is known about the developmental preconditions and functions of INS in childhood. This paper presents a developmental framework for understanding INS, integrating insights from structural and functional brain maturation, as well as behavioral, social, and cognitive development. We discuss how early caregiver-infant interactions, characterized by shared perceptual rhythms, facilitate the emergence of INS. Given initial limitations in temporal precision of neural processing, early INS is likely constrained to low-frequency brain rhythms and evolves alongside the maturation of neural networks and socio-cognitive abilities. We outline how INS may support critical developmental processes, including social learning, language acquisition, and attachment formation, through enabling mutual prediction and co-regulation between caregivers and children. Furthermore, we hypothesize that tasks requiring higher-order mutual understanding are linked to qualitative changes in INS patterns over time. This framework highlights the potential of INS as both a marker and a driver of developmental change, offering new avenues for research and intervention. Longitudinal studies and rhythm-based interventions could deepen our understanding of how INS supports development, with implications for enhancing social learning and attachment in populations at risk for developmental challenges. This work underscores the importance of adopting a developmental perspective in INS research.