Abstract:
This dissertation examined Repetitive and Restricted Behaviors and Interests (RRBIs) in children and adolescents with Autism Spectrum Disorder (ASD). We looked at RRBI ratings from the respective subscales of the Autism Diagnostic Observation Schedule (ADOS; Lord et al. 2000), a clinician observation, and the Autism Diagnostic Interview-Revised (ADI-r; Le Couteur et al., 2003), a parent developmental history report. The purpose was to explore (1) whether RRBIs total scores diminish as individuals with ASD get older, (2) whether RRBIs are a cohesive, unitary construct or whether there are distinct subtypes of RRBIs, and (assuming that there are RRBIs subtypes) whether these subtypes show different trajectories across age and intellectual functioning, and (3) to what extent the ADOS and ADI-r RRBI subscales cross-validate one other. Exploratory and confirmatory factor analyses for the ADOS and ADI-r resulted in two-factor models, which we labeled as Cognitive-Restrictive and Motor-Sensory. For total RRBIs, Cognitive-Restrictive RRBIs, and Motor-Sensory RRBIs, adolescents showed significantly lower impairment ratings than younger age groups. Total RRBI ratings were negatively associated with IQ scores for both instruments. However, examining the RRBI subscale scores separately revealed that only Cognitive-Restrictive ratings had a negative association with IQ scores. Ratings for the Motor-Sensory scale were not associated with IQ. On the ADI-r, a significant interaction showed that Cognitive-Restrictive ratings were higher and unchanging for lower-functioning individuals across age groups. Higher-functioning individuals showed lower ratings across each age group. We also found that RRBI items from the ADOS and the ADI-r correlated relatively poorly across the measures. Our study provides evidence for the two-factor model of RRBIs, though distinctions from prior researchers' models are highlighted.
