Executive functions in Asperger's syndrome: An empirical investigation of verbal and nonverbal skills

Deficits in executive functioning (EF) have been proposed to underlie the behavioural patterns of individuals with an autism spectrum disorder. Researchers have shown that the Asperger's syndrome (AS) population performs more poorly than typically developing controls on many EF tasks. However, the research literature is inconsistent in identifying the specific features or aspects of EF that are affected in this population. This study investigated EF in AS using a bottom-up empirical method. Four visually mediated and three verbally mediated EF tasks from the Delis–Kaplan Executive Functioning System were administered to 33 adolescents with AS and 33 age- and gender-matched controls. Two-step cluster analysis was then used to derive subgroups. Diagnostic composition of these subgroups (AS versus control) was examined to provide empirical evidence of a performance bias towards verbal EF for the AS group. A two cluster solution best fits the data with 73% of the AS participants being classified into one cluster and 64% of the control participants classified into another. Assignment into cluster A was based primarily upon low performance on the four visual EF tasks whereas assignment into cluster B was based primarily upon good performance on the four visual EF tasks and one verbal EF task.

► Executive functions were examined in adolescents and young adults with Asperger's syndrome (AS).
► We examined modality-specific performance on executive function (EF) tasks.
► Individuals with AS demonstrated better verbal EF skills with some heterogeneity.
► These skills were largely unrelated to cognitive intelligence (IQ).
► The study provides a framework by which to understand EFs in this population.