High functioning autism vs. Asperger’s: the VIQ PIQ myth?

A review of: Spek, A.A., Scholte, E.M., Berckelaer-Onnes, I.A. (2008). Brief Report: The Use of WAIS-III in Adults with HFA and Asperger Syndrome. Journal of Autism and Developmental Disorders, 38(4), 782-787. DOI: 10.1007/s10803-007-0446-5

I have documented in previous posts that clinicians and researchers have often proposed that high functioning autism and Asperger’s present a significantly different neurocognitive profile (see here and here). The belief is that children with AS tend to have a significant discrepancy between verbal and non-verbal abilities, with relatively higher verbal functioning as compared to non-verbal skills. On the other hand, children with high functioning autism tend to have relatively equal verbal and non-verbal skills. However, recently I’ve been encountering several studies that suggest that this may not be the case. As reported in this brief yet very elegant study from the Leiden University in the Netherlands, the researchers conducted a cognitive assessment of 16 adults with high functioning autism and 27 adults with Asperger’s syndrome using the WAIS-III (the most common adult IQ assessment instrument). Diagnoses were confirmed via ADI using DSM-IV criteria to differentiate HFA vs. AS. There were no differences between the groups in verbal vs. non-verbal performance (VIQ vs. PIQ). There was no pattern of high-verbal low-non-verbal scores in the Asperger’s group, with both groups scoring in the High Average range for both verbal and non-verbal composite scales. However, one global factor scale difference was observed. Adults with high functioning autism showed a significantly lower Processing Speed as compared to other factor skills such as Verbal Comprehension, Perceptual Organization, and Freedom from Distractibility. This finding was not observed in the Asperger’s group. Despite this difference (and some additional task-specific differences I didn’t mention in this review), the general findings of this study fail to support the idea that people with high functioning autism and Asperger’s can be differentiated on the basis of relative strength and weaknesses in their verbal vs. non-verbal performance as measured by standard intellectual assessment batteries.

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