How Do the Functions of Restricted and Repetitive Behaviors Vary with Developmental Level in Children with ASD?

Background:  The Motivation Assessment Scale (Durand & Crimmins, 1992) is a caregiver questionnaire designed to identify the functions of target behaviors. Joosten et al. (2009) modified the MAS for use in relation to repetitive behaviors in children with ASD, and shed light on how the functions of repetitive behaviors in children with ASD differ from the functions of repetitive behaviors in children with developmental delay. The functions addressed by the scale, as conceptualised by Joosten et al., are Intrinsic (controlling sensory feedback; responding to anxiety), and Extrinsic (gaining attention; escaping [from demands]; gaining tangible reward). Little is known about how the functions of repetitive behavior vary by developmental level.

Objectives:  Building on Joosten et al.’s group comparison, we sought to investigate the extent to which the functions of repetitive and restricted behaviors (RRBs) vary with developmental level in children with ASD, extending this analysis to both lower-level (repetitive motor and sensory behaviors) and higher-level (insistence on sameness) behaviors.

Methods:  Telephone interviews were conducted with parents of 2- to 17-year-olds with clinical diagnoses of ASD. As part of the telephone interview, each participant completed one modified-MAS for each of their child's most frequent RRBs, with frequency measured by the Repetitive Behaviours Questionnaire-2. The mean scores for intrinsic and extrinsic function were used for analysis—firstly, averaging across all RRBs, and, secondly, averaging for lower-level and higher-level behaviors separately. Expressive language level was used to index developmental level. This was assessed during the telephone interview using items adapted from the Diagnostic Interview for Social and Communication Disorders (Wing et al., 2002), and the resulting 7-point scale ranged from 0 (no speech or meaningful vocalisations) to 6 (uses past, present and future tenses and complex sentences).

Results:  Preliminary analysis of data from 27 participants indicates a positive relation between developmental level and extrinsic function, r(26) = .41, p < .05. This remained even when lower-order RRBs alone were considered, r(18) = .48, p < .05. Multiple regression with the three extrinsic subscales predicting developmental level showed that escaping was related to developmental level (β = .48) but gaining attention and gaining tangible reward were not (βs -.01 and .02 respectively). Intrinsic function was heavily endorsed in relation to children of all developmental levels and was unrelated to developmental level, r(26) = .19, ns.

Conclusions:  These data suggest that the functions of repetitive behaviours are more diverse in children with higher developmental level, with extrinsic function assuming greater importance than in children with lower developmental level. Specifically, a new function of escaping emerges with increasing developmental level.