Subtypes of Restricted and Repetitive Behaviors in Minimally Verbal Children with Autism Spectrum Disorders

Background: Restricted and repetitive behaviors (RRBs) are a core feature of the autism phenotype. Research analyzing the factor structure of the RRB items on the ADI-R has provided evidence for at least two RRB subcategories: repetitive sensory motor (RSM) and insistence on sameness (IS) behaviors (Cuccaro et al., 2003; Szatmari et al., 2006; Richler, Bishop, Kleinke & Lord, 2007). Alternatively, factor analyses of the Repetitive Behavior Scale Revised (RBS-R) have primarily supported a five-factor model of RRBs: Sensory-Motor, Self injury, Compulsive, Ritualistic/Sameness, and Restricted Interests (Lam & Aman, 2007). Recently, Bishop et al. (2013) examined relationships between the factors of the ADI-R, factors of the RBS-R, and other child characteristics. The ADI-R RSM and IS factors were significantly correlated with the RBS-R Sensory-Motor and Ritualistic/Sameness factors, respectively. These pairs of matched factors exhibited similar relationships with other child variables as well. These findings support the construct validity of the RSM and IS subcategories of RRBs in ASD. However, because studies examining the RSM and IS subcategories have utilized larger, more heterogeneous samples of children with ASD, it is possible that RRB subtypes organize differently in specific groups of children within ASD (i.e., nonverbal children), and that these differences get lost in these larger samples.

Objectives: The primary aim of this study is to test whether RSM and IS scores on the RBS-R and ADI-R exhibit similar cross-measure relationships in a minimally verbal sample of children with ASD. 

Methods: Participants will include at least 50 children (4-8 years of age) who enrolled in a randomized clinical intervention trial and were assessed prior to receiving treatment across four sites. All children were classified as minimally verbal through parent report and the use of a naturalistic language sample (<20 spontaneous words in 20 minutes). ASD diagnoses were confirmed with the ADOS-2 and ADI-R, cognitive abilities were measured with the MSEL and Leiter-R, and parent report of restricted and repetitive behaviors were collected with the RBS-R.

Results: Data collection is ongoing. Preliminary analyses suggest similar relationships between the RSM and IS subscales on the ADI-R and RBS-R as in previously published papers (Bishop et al., 2013). ADI-R RSM scores were correlated with the RBS-R Sensory-Motor subscale (r = 0.69); similarly, IS scores on the ADI-R were correlated with the RBS-R Ritualistic/Sameness subscale (r= 0.58). Subsequent analyses will confirm the presence of the RSM and IS factors within the ADI-R in this specific sample and further examine relationships between these factors and subscales on the RBS-R. Additional analyses will explore whether these subtypes of behavior are associated with other child variables in ways similar to those seen in larger samples.    

Conclusions: If, as we anticipate, the results from this minimally verbal sample correspond to previously published findings, the current study will further support the validity of the RSM and IS subcategories of RRBs. If the factors do not exhibit relationships that are similar to those reported in previous studies, this would have implications for measurement of RRBs in children with low language abilities.