A review of: Barnard, L., Muldoon, K., Hasan, R., O’Brien, G., Stewart, M. (2008). Profiling executive dysfunction in adults with autism and comorbid learning disability. Autism, 12(2), 125-141. DOI: 10.1177/1362361307088486

In this well designed study, the authors first reviewed the basic theory of Executive Function. Executive function (EF) refers to neurocognitive processes associated with the planning and implementation of actions. Some researchers have proposed that autism is directly linked to anomalies in EF. Deficits EF lead to difficulty in the planning and initiation of action, inhibition of inappropriate responses, and difficulty with strategy monitoring. One issue in assessing EF in children and adults with autism is that deficits in EF are also present in other developmental problems, such as learning disabilities, which are common in people with autism. In order to control for this possible confound, the authors compared 20 adults with autism and co-morbid learning disability against 23 adults with learning disability only. These two groups were matched for age and IQ. The authors compared their performance on a battery of neuropsychological tests of EF*. The authors found that although the group with autism performed consistently worse than the group with learning disabilities on all tasks, none of these differences reached statistical significance. The authors then created a composite score of different domains of EF and found significant differences between the groups. Specifically, the group with Autism had significantly lower scores on ‘working memory’ and ‘planning’. A few specific factors about this study are worth mentioning. The study was conducted with adults with intellectual impairment (Average IQ = 67), thus the findings may not generalize to people within the normative range of intellectual functioning. The sample size was also extremely small, which affects the ability to find statistically significant differences. Finally the authors discussed one interesting point regarding “causality”. It is difficult, if not impossible, to understand the direction of the causal factors at play. Is executive functioning one contributing factor to autism (a possible cause), or is it simply a byproduct of other impairments related to autism (caused by)?

*For those interested in the specific tasks used, these included the: Tower of London, Mazes, the Knock and Tap task, Verbal Conflict, WCST, COWA, Non-verbal Fluency, and the WMS-III.

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