Investigating the Structure of Restricted and Repetitive Behaviours in High-Functioning ASD

Background:  

By definition, people with Autism Spectrum Disorder (ASD) have Restricted and Repetitive Behaviours (RRBs); and these have implications for their adaptive function, capacity to learn and well-being.  Despite this RRBs have received relatively little attention from researchers compared to the social-communication aspects of the autism syndrome. In Turner’s (1999) annotation of research conducted on RRBs, she identified two broad categories of RRB -  ‘lower-order’ and ‘higher-order’ behaviours. It was argued that these represent continua that extend through the general population. Lower-order RRBs are defined as repetitive movements with objects and the body, whereas higher-order RRBs are related to object attachments, insistence on sameness, circumscribed interests and repetitive language. It is suggested that lower-order RRBs are related to lower intellectual abilities; whereas higher-order RRBs are associated with impairments in the meta-cognitive processes encompassed by executive functioning. ‘Executive functioning’ can be loosely defined as a gathering of frontally mediated processes which are accountable for planning, cognitive flexibility, conceptual thinking, rule acquirement, instigating suitable actions and inhibiting unsuitable actions, and accepting significant sensory information. These are precisely the processes that are impaired in ASD.

Objectives:  

The current study examined RRBs by evaluating Turner’s (1999) theory that they can be divided into lower-order and higher-order categories, distinguished by intellectual ability.

Methods:  

The RRB questionnaire is part of the Developmental, Dimensional and Diagnostic Interview (3di). This is a widely used, well validated diagnostic tool is used to assess developmental disorders in children. The 3di was administered to 40 children with a FSIQ of ≥70.  Quantitative methods of correlation analysis, non-metric multidimensional scaling (Shiffman, Reynolds & Young, 1981) and multiple regression were used to analyse the data.

Results:  

Analysis of the 3Di questions showed using non-metric multidimensional scaling revealed that the RRB questionnaire was uni-dimensional measure; there was no evidence for a distinction between higher- and lower- order RRBs.  No correlation was found between RRBs and FSIQ. Multiple regression showed only one question from the RRB questionnaire, which concerned the all-absorbing nature of special interests for those with ASD, to be a significant predictor of FSIQ.

Conclusions:  

These findings suggest that, contrary to Turner’s theory-based predictions, RRBs (as measured by the 3Di) are best conceptualised as manifestations of a single latent trait dimension.  RRBs were not associated with lower intellectual ability. An implication for education is that the presence of severe RRBs is not indicative of low intellectual ability; and are relevant to high-functioning ASD. Further research with larger samples will be required to fully investigate the latent structure of RRB.