Movement Coordination's Link with Common Ground During Dyadic Peer Discourse in Typically Developing and Autistic Speakers.

Common ground (CG)-a pragmatic capability that reflects the construction of shared meaning by two interlocutors during conversation-is widely accepted as crucial for effective communication, but its exploration has been limited in the context of children's peer-to-peer interaction. Specifically, this study aimed to explore CG differences between typically developing (TD) and autistic populations, CG's developmental trajectories, as well as the link between CG and motor coordination skills during peer interactions. Study participants included 148 children (6-16 years), comparing 64 TD and 84 autistic children across three age levels. Fixed dyads matched on IQ, age, sex, and mother's education performed a CG tangram-card task and complementary joint action (JA) tasks to evaluate peer-to-peer movement coordination. Individual motor skills were also assessed. As expected, both autistic and TD groups showed increasing efficacy over the 6-turn CG task (fewer words and shorter duration to communicate), although autistic participants were less efficient than TD participants. Better motor skills and JA synchronization correlated with both groups' more efficient CG performance. Additionally, the indirect relationship between group (TD/autism) and CG was mediated by motor skills and JA, with age moderating the relationship between JA and CG. Specifically, better motor skills and socio-motor coordination were associated with more efficient CG creation, particularly in younger children (under 10 years). These findings suggest potential novel avenues for early interventions targeting motor and language challenges in autism to enhance pragmatic abilities and peer interactions, offering insights into language development in this population.