Abstract
Repetitive and stereotyped behaviors (RSB) constitute one of the three core diagnostic domains of autism spectrum disorders (ASD). However, relatively little is known about the behaviors in this domain, as compared to behaviors in the social and communication diagnostic domains, particularly early in the development of ASD symptoms. This prospective longitudinal study examined RSB between 18 and 24 months of age in children who were later diagnosed with ASD (n=50), and matched groups of children with developmental delays (DD) in whom ASD had been ruled out (n=23) and children with typical development (TD, n=50). Precise measures of proportion and rate of RSB for each child were obtained through systematic observation of behavior samples from the Communication and Symbolic Behavior Scales Developmental Profile (Wetherby & Prizant, 2002). Children with ASD demonstrated significantly higher proportion and rate of RSB with objects, RSB with body, and total RSB than TD children and significantly higher proportion and rate of RSB with objects and total RSB, but not RSB with body than children with DD. In addition, a unique linear combination of RSB distinguished children with ASD with rotating/spinning/rolling objects and stiffening the arms and hands contributing most strongly to this combination. In the children with ASD, RSB was not related to social competence or eye gaze to face in the second year. In addition, only RSB with body and total rate of RSB were significantly correlated concurrently with developmental level in the second year. There were modest relationships between RSB in the second and fourth years of life. Social and developmental functioning in the second year predicted RSB and social symptoms in the fourth year. The results have important implications for early identification of ASD. The findings are consistent with the notion that social and nonsocial (RSB) symptoms may be subserved by separate underlying mechanisms in the second year of life.
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