Nonlinear dynamics of parent–child cardiac coupling during play in autism: A multimodal investigation of sociobehavioral correlates

Dyadic coordination, the temporal organization of behavioral and physiological processes in two interacting partners, plays a vital role in social development and may reveal biobehavioral mechanisms underlying social differences in autism. However, little is known about how dyadic physiological processes such as cardiac coupling vary across social engagement contexts in autism. This exploratory study examines cardiac coupling patterns among 18 parent--child dyads during play and compares autistic dyads to neurotypical dyads with respect to time-varying joint engagement, vocal turn-taking, and child social communication ability. Using cross-wavelet analysis to measure ambulatory cardiac interbeat interval (IBI) coherence and phase relationships (alignment and directionality), and cross-recurrence quantification analysis to measure vocal turn-taking dynamics, our results suggest that cardiac coupling varies systematically across joint engagement contexts and that these associations are stronger and more differentiated in dyads with autistic children than in neurotypical dyads. Greater high-frequency cardiac coupling in the autism group was associated with periods of mutual disengagement and with fewer, shorter, and less predictable vocal exchanges. Average IBI coherence also accounted for a substantial proportion of variance in children's social communication scores in the autism group, but only a small proportion in the neurotypical group, suggesting that cardiac coupling is particularly sensitive to individual differences in social communication among autistic children. Together, our findings underscore the potential utility of examining physiological coupling to better understand social engagement processes and suggest that cardiac coupling may serve as a marker of both moment-to-moment engagement dynamics and broader social communication heterogeneity in autism.