Response Shifting and Inhibition in Preschoolers with Autism Spectrum Disorder

Background: Executive functions (EF) encompass a variety of skills including those that begin to develop early (working memory and inhibition) and those that begin to develop later in childhood (planning and self-monitoring). Previous studies with children and adolescents found that individuals with autism spectrum disorder (ASD) show impairment on EF tasks requiring mental flexibility and intact performance on tasks requiring inhibitory control (Ozonoff, South & Provencal, 2007). Few studies have examined EF in preschool-aged children with ASD and these studies have largely failed to demonstrate specific EF deficits (Griffith et al., 1999; Dawson et al., 2002). Further, EF deficits in older individuals with ASD have been linked to developmental delay suggesting that EF may be a result of cognitive impairments rather than an autism-specific symptom.

Objectives: The purpose of this study was to examine inhibitory EF in preschool children with ASD. Particularly of interest was the potential relation between other cognitive skills and EF early in development. Thus, links between EF and standardized developmental measures and measures of imitation were examined.

Methods: Participants included 25 young children with ASD (chronological age: mean = 43 months; range 25-68 months) and two groups of children with typical development (29 matched on chronological age, mean = 43 months; 28 matched on receptive language ability, mean = 37 months). The Mullen Scales of Early Learning was administered to measure nonverbal abilities as well as receptive and expressive language. Children completed an assessment of imitation, the Motor Imitation Scale (MIS; Stone et al., 1997) and two EF measures of inhibition, A-not-B Task and Gift Wrap Delay. 

Results: EF was measured by overall performance and error rates. Compared to chronological-aged matched children with typical development, children with ASD showed similar levels of EF, all t(52)<1.66, all p’s>.10. Compared to receptive language ability matched children with typical development, children with ASD showed similar levels of EF, all t(51)<1.28, all p’s>.20. For children with ASD, correct choices on the A-not-B Task were significantly positively correlated with standard scores on nonverbal development and language (r’s>.43, p’s<.032) and measures of imitation (r’s>.40, p’s<.047). On the Gift Delay task for children with ASD, number of times peeked while waiting was significantly negatively correlated with expressive language and overall Early Learning Composite (r’s<-.41, p’s<.041). Data for both groups of children with typical development were combined for correlation analyses. For all children with typical development no significant correlations were found between any EF measure, imitation, nonverbal or verbal abilities. 

Conclusions: Results support the notion that inhibitory EF is not impaired in preschool-aged children with ASD. No relation between EF and developmental level was found in children with typical development, whereas for children with ASD better performance on EF was related to overall cognitive ability (expressive language and visual reception skills) and imitation ability. The causal relation between early developmental delays and later EF impairments is largely unknown. However, for children with ASD, language development and overall cognitive development could have important implications for the later development of EF ability.