Cues For Synchrony: Exploring Social Drivers of Synchronous Interactions Across Neurodevelopment

When we interact with others, we coordinate our behaviour and neurophysiology. This process, known as interpersonal synchrony (IS), is crucial effective social communication across the lifespan. Understanding the developmental drivers of synchrony can inform how to nurture social connections across development and neurodevelopmental profiles. This doctoral dissertation explores the mechanisms underlying IS, focusing on its developmental roots and variability in Autism Spectrum Disorder (ASD). In Study 1, I examined how early caregiver-infant interactions shape the infant’s developing brain networks. I found that synchronous interactions predict stronger long-distance neural connections, with increased functional connectivity associated with greater caregiver engagement and the incidence of affectionate touch during moments of infant social attention. I argue that sensitive caregiving – where adults attune to the infant's cues and respond appropriately – scaffold the development of infants’ functional connectome. If interpersonal synchrony serves as a “social glue”, it is plausible to hypothesise that socio-communicative difficulties may be accompanied by, and potentially partly attributable to, atypical interpersonal synchrony. In Study 2, I conducted meta-analysis synthesising research on interpersonal motor synchrony in ASD. I found significant variability across studies, with more ecologically valid tasks yielding stronger synchrony effects. This finding highlights the complexity of synchrony, which emerges from the dynamic interplay between partners, each bringing their own individual characteristics into the social exchange. However, existing literature often fails to account for these nuances. Delving into individual factors influencing synchrony, in Study 3 I explored how individuals prioritise time contingency and social engagement in interactions. I found that both neurotypical and autistic participants preferred socially engaging and timely responses, but distinct patterns emerged in socially engaging situations where time contingency was disrupted. Neurotypical participants compensated for a lack of time contingency with social engagement, whereas autistic participants preferred stimuli that were both timely and engaging. I argue that creating predictable and engaging social environments can help individuals with ASD feel more comfortable and connected in social settings. The general discussion highlights the dynamic and reciprocal nature of interpersonal synchrony, illustrating how mutual coordination can be seen as a rhythm shaped by both partners. Reflecting on the implications of this research, I suggest that the varying levels of synchrony often seen in cases of parental depression, anxiety, and autism spectrum disorders may stem from difficulties both partners experience in aligning their behaviours, a perspective that is often neglected by literature that tends to attribute the difficulties to the “neurodiverse” component of a dyad. By understanding and harnessing the key factors that drive interaction choices, we can open up new avenues for promoting positive outcomes and strengthening social connections across diverse neurodevelopmental profiles. This perspective advocates for a holistic, dyadic approach in future research, one that appreciates diversity by recognising the unique strengths of each partner, which often precede their challenges.