Restrictive and Repetitive Behaviors and Interests and Inhibitory Control in Children with Autism Spectrum Disorder

Background:  Deficits in executive functioning (EF), an ability that encompasses inhibition, planning, attention regulation, set-shifting and working memory, have been observed in children with autism spectrum disorders (ASD) (Ozonoff, Pennington, & Rogers, 1991; Pellicano et al., 2006). Poor inhibitory control has been implicated in the maintenance of the inappropriate (i.e. nonadaptive) thoughts and behaviors distinctive of ASD, termed restrictive and repetitive behaviors and interests (RRBIs) (Turner 1997; 1999). This characteristic can be subdivided into two correlated yet qualitatively different categories: Insistence on Sameness (IS) and Repetitive Sensory Motor (RSM) behaviors (Turner, 1999; Somer et al., 2013) and conceptualized as higher-order (including preoccupations and ritualistic behavior) and sensorimotor, respectively (Mosconi et al, 2011; Turner, 1999). RRBIs generally, and higher-order RRBIs specifically, have been related to inhibitory control in individuals with ASD with mixed results (Lopez et al., 2005; Mosconi et al. 2009). In the present study, inhibitory control and phenotypic variation in RRBIs were examined in 64 high-functioning children with ASD.

Objectives:  To determine whether variation in RRBIs relates to impaired inhibitory control in a Stroop task in children with ASD.

Methods:  64 children with ASD between the ages of 7- and 12-years-old were included in analyses. All children had a full-scale IQ above 85. Children participated in the Autism Diagnostic Observation Schedule (ADOS-2) and parents completed survey and interview measures about their child, including the Repetitive Behavior Scale-Revised (RBS-R) and Autism Diagnostic Interview-Revised (ADI-R). Children's behavioral responses were recorded during a computer-based Stroop task. Stroop difference scores were computed from accuracy scores on incongruent and congruent trials, with larger difference scores indicating a failure to inhibit a learned verbal response. Children's inhibitory control in the Stroop task was analyzed with parental reports of RRBIs on the ADI-R and RBS-R, and researcher ratings of RRBIs during the ADOS-2. Higher-order RRBI scores were computed from subscale items on the ADOS-2, ADI-R, and RBS-R.

Results:  Correlations between higher-order RRBI scores on the ADI-R and RBS-R and Stroop difference scores were not significant, however higher-order scores on the ADOS-2 were positively correlated with Stroop difference scores (r = .292, p = .019). A linear regression controlling for age and verbal IQ found a significant relationship between higher-order ADOS-2 RRBIs and Stroop difference scores (R²_change = .075, t(62) = 2.27, p = .027). No relation was found between global RRBI subscales from the ADOS-2, ADI-R, or RBS-R and Stroop performance.

Conclusions:  RRBIs were inconsistently related to inhibitory control; however findings suggest readily observable higher-order RRBIs (e.g. via the ADOS-2) may be more indicative of children's current inhibitory skills than parental reports. Analysis of participants' behavioral and electrophysiological responses to a Go-No-Go task is ongoing and will allow further examination of inhibitory control as it relates to RRBIs. Given the significant interference of RRBIs in everyday functioning, computer-based EF training may be an efficacious and desirable intervention for reducing higher-order RRBIs through improved inhibitory control.