Interpersonal Coordination and Its Role in Social Functioning in ASD

Background: Interpersonal coordination (IC) is the tendency for social partners to nonconsciously align their behaviors. It is a well-established phenomenon from infancy, and has been shown to foster connectedness, enhance processing of social cues, and play an important role in development. A small body of research has begun to suggest atypical IC in autism spectrum disorder (ASD). This study augments that research by evaluating differences in both nonverbal and verbal IC as contributors to social symptoms in ASD.

Objectives: (1) To quantify the degree to which children with and without ASD engage in IC; (2) To identify the extent to which engaging in IC relates to aspects of social functioning impaired in ASD.

Methods: Participants were 20 well-characterized children (ages 9-16) with ASD and 17 matched typically developing controls (TDC). Children participated in conversational tasks with their mothers and an unfamiliar research assistant. IC during these tasks was coded from recordings by blinded raters, using two established coding systems. The first captured temporal coordination among interaction partners’ movements (movement coordination); the second captured IC in terms of the verbal content of interactions (content coordination; e.g., mutual focus, conversational equality). Interrater reliability was adequate for all codes (ICCs .77-.96). Children’s everyday social functioning was also assessed with standardized measures completed by mothers, in the domains of general social skills, communication skills, empathy, and perspective-taking.

Results: Movement and content coordination were analyzed separately with mixed design ANOVA. There was a significant main effect of group for both movement coordination, F(1,34)=17.65, p<.001, η_p²=.34, and content coordination, F(1,34)=7.21, p=.01, η_p²=.18. In both cases, children with ASD were rated as displaying significantly less IC with their interaction partners than TDC children. Neither within-subjects effects of familiarity level nor interaction terms were significant. Within the ASD group, both movement coordination, r(17)=-.64, p=.003, and content coordination, r(17)=-.59, p=.01, were significantly correlated with symptom severity as measured by ADOS-2 calibrated severity scores. Linear regression analyses across all children indicated that movement coordination predicted scores on standardized measures of general social skills, communication skills, empathy, and perspective-taking, even when controlling for content coordination (all βs≥.39; ps<.05). Content coordination, however, did not predict any social outcome domain when controlling for movement coordination (all βs≤.15; ps>.05). Finally, movement coordination partially mediated the relationships between diagnostic status and both general social skills and communication skills.

Conclusions: Results demonstrate reduced nonverbal (movement) and verbal (content) IC in children with ASD, suggesting atypicality in their ability to engage in a social process that is automatic and fundamental in normative development. Results also strongly link IC to primary areas of social impairment in ASD. Lower IC was associated with more severe ASD symptoms, suggesting a relationship with core diagnostic deficits. Moreover, movement coordination specifically predicted functioning across several key social domains, raising the possibility that a failure by individuals with ASD to coordinate movements with social partners may help explain social difficulties. Findings thus highlight atypical IC as an important, understudied process in ASD, which may be a mechanism driving social and communication impairments.