Inhibitory Control in Young Children with Autism Spectrum Disorder

Background: Inhibitory control (IC) is a higher-order executive function involved in suppressing a prepotent response in order to produce an appropriate, task-relevant response (Diamond, 2013). IC experiences rapid growth during the early school years (MacDonald et al., 2014) and is associated with social-emotional ability (Rhoades et al., 2009), emotion regulation (Carlson & Wang, 2007), and early mathematics (Clark et al., 2010) in young children with typical development (TD). While there is strong support for the presence of executive function deficits in autism spectrum disorder (ASD), the IC abilities of individuals with ASD is still debated (Christ et al., 2007; Ozonoff & Strayer, 1997). Very little is known about the IC profile of young children with ASD, but recent research found no group differences on a behavioral measure of inhibition in toddler- to early school-aged children with ASD compared to TD peers (Gardiner et al., 2017).

Objectives: Our primary objective was to explore the relation between different child factors (ASD vs. TD, chronological age, and sex) and IC in a sample of young children.

Methods: Participants included 159 children, 36- to 83-months of age, with TD (n = 102) and ASD (n = 57). Child’s diagnostic status was determined by diagnostic reports provided or medically released by parents. Verbal ability was assessed using a composite verbal domain standard score obtained from the Differential Ability Scale-II (Elliot, 2007). Children were administered the Boy-Girl Stroop Task (Kerns & McInerney, 2007; adapted from Diamond et al., 2002) to measure IC, operationalized as the number of correct responses (highest score = 16).

Results: Multivariate regression analysis was used to examine the relations among status (ASD vs TD), age, verbal ability, and sex. The analysis indicated that verbal ability, sex, and age explained a significant proportion of unique variance in IC (R² = .11, F(4,154) = 5.72, p < .001) with higher verbal ability predicting higher IC (b = .05, t(154) = 2.19, p =.03), older children predicting higher IC (b = .08, t(154) = 3.34, p = .001), and females (M = 13.61, SD = 3.15) outperforming males (M = 12.11, SD = 4.19; b = -1.34, t(154) = -2.17, p = .03). No differences in IC were found between children with ASD (M = 12.11, SD = 4.33) and TD (M = 13.03, SD = 3.58; b = .59, t(154) = 0.87, p = .38).

Conclusions: This study demonstrated that verbal ability, age, and sex predict IC in young children. No differences were found between children with ASD and TD peers for IC. These findings are consistent with research demonstrating that IC in school-aged, TD children improve with age (MacDonald et al., 2014) and that children with TD and ASD perform similarly on laboratory tasks of IC (Gardiner et al., 2017). This is the largest and youngest sample to date exploring the relation between ASD and IC. Further research is needed to better understand how inhibition develops in young children with ASD.