Longitudinal Dynamics in Atypical Development: Mutualistic Coupling in Autism?

Background: Autism is a behaviorally-defined neurodevelopmental condition based on diagnostic criteria such as social and communication difficulties and repetitive and restrictive behavior. Currently, the field is moving away from the theoretical stance that these behaviors have a common cause, yet little is known about the dynamic processes that drive the co-development of these characteristics.

Objectives: Using a longitudinal design, the aim of the study presented here was to model the parallel growth of social and non-social autism-related behaviors in a cohort of infants at-risk for atypical development.

Methods: Receptive language and fine motor skills were assessed on four measurement occasions in a group of 239 infants (122 girls and 117 boys, aged 6-36 months). Longitudinal growth curve analyses were applied to investigate the cross-domain coupling of longitudinal changes in these domains.

Results: Our results suggested that improvement in language goes hand-in-hand with improvement in motor skills, and vice versa. We did not, however, find compelling evidence for mutualistic coupling between these skills. Group differences were observed in the variance of both, the trajectories and the initial starting values of both language and motor skills.

Conclusions: Our results suggest that those children receiving a diagnosis of atypical development at age three are not specifically characterized by increased or decreased coupling between language and motor skills compared to their at-risk peers who do not receive a diagnosis.