Executive function and autistic symptomatology in very young children
The Executive Function hypothesis proposes that the behavioural aspects of autism can be explained by impairment in executive function skills. The term 'executive function' refers to several cognitive skills including inhibitor)'control, generation of novel responses, working memory and planning. Many studies have demonstrated that school-aged children, adolescents and adults with autistic spectrum disorders are impaired on tasks designed to measure these skills (Pennington & Ozonoff, 1996). However, despite the early onset of this developmental disorder, little work has explored the executive functioning of pre-school children with autism, hi a developmental context, the executive function hypothesis would predict early executive deficits for children with autistic spectrum disorders, an association between executive function skill and symptom severity, and a relationship between the developmental trajectories of executive function and behavioural profiles. The present study recruited three-year-old children referred for autistic spectrum disorders or speech and language delay. A battery of executive function tasks measuring inhibition, working memory and planning was administered on recruitment and one year later. Detailed behavioural information was also gathered at both time points. Cross-sectional group comparisons revealed little evidence for an executive deficit in children with autism at either age. Similarly, there were no reliable relationships between executive performance and symptomatology. At a group level behavioural scores appeared to change little over the year. However, within each group there was evidence for both positive and negative change. Moreover, executive function performance did not change reliably across individuals over the year, nor was there any consistent relationship for individual children between performance on one executive function task and one behavioural domain. These findings are discussed in relation to the psychological theories of autism, and implications for intervention approaches are considered.