Determining Synchrony of Mother-Infant Non-Verbal And Movement Behaviours Using First-Person Observation and Accelerometer Data

Abstract

Mother-infant synchrony—the dynamic, coordinated exchange of behaviours and movements between caregivers and their infants—is fundamental for promoting healthy emotional, cognitive, and socio-emotional child development. Despite extensive global research, current evidence remains predominantly derived from Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies, raising questions about its generalizability to low-resource and culturally diverse contexts such as South Africa. This thesis aimed to address this critical gap by exploring synchrony using innovative multimodal methodologies, specifically first-person observational approaches via head-mounted cameras (headcams) and wrist-worn accelerometer, within a socioeconomically constrained urban South African setting (Soweto). Three interconnected studies were conducted among mother-infant dyads at critical developmental periods (4 and 8 months postpartum) to assess patterns, determinants, and developmental trajectories of non-verbal behavioural and movement synchrony. Study one employed headcam footage to provide intimate, ecologically valid insights into everyday caregiver-infant interactions, highlighting delays in the emergence and stability of synchronised behaviours compared to high-income contexts. Study two utilised accelerometer data to objectively capture mother-infant movement patterns, revealing detailed temporal synchrony particularly during caregiving routines and demonstrating a developmental shift from mother-led to infant-led coordination. The final study, a longitudinal analysis combining both methodologies, identified maternal employment as a consistent predictor of reduced synchrony, underscoring how structural constraints significantly influence relational caregiving capacities. iv | P a g e Collectively, these findings affirm that synchrony is a dynamic, developmentally evolving process substantially influenced by caregiving context and availability. The integration of first- person observational and accelerometry methods provided robust, objective data, overcoming biases associated with traditional observational techniques. This methodological innovation represents a significant advancement in synchrony research, particularly for low- and middle- income countries. Furthermore, findings hold practical implications for developing culturally sensitive, synchrony-focused early childhood interventions and policy frameworks designed to mitigate developmental risks associated with socioeconomic adversity. Future research recommendations include extending longitudinal assessments, explicitly incorporating maternal mental health and psychosocial variables, broadening the scope to include multi-caregiver roles, and employing qualitative methodologies to enrich contextual understanding. This thesis thus lays critical groundwork for enhancing early developmental outcomes through evidence-based, culturally responsive synchrony interventions tailored to the South African caregiving landscape.