A psychological investigation of autistic spectrum disorders : implications for the concept of Asperger syndrome
Asperger Syndrome was first described in 1944. Because of its similar presentation with autism it was subsumed under autistic spectrum disorders about 35 years later. The present study re-assessed Asperger's original article and identified specific differences between the two conditions leading to the hypothesis that Asperger Syndrome was different from autism. This was examined in four areas: cognitive profiles, cognitive styles, language and motor skills. A test battery of 11 standardised and non-standardised tests was used to examine the hypothesis. Medical consultants classified 50 participants, from 5 to 10 years of age, with autistic features on the basis of both the DSM-IV criteria for autism and Asperger Syndrome and, separately, Gillberg and Gillberg's (1989) criteria. The results showed very low agreement for either with consultants' overall diagnostic impressions, indicating poor validity of these three diagnostic instruments, which consequently did not allow allocation of participants into groups of autism and Asperger Syndrome. The classification was finally based on parental ratings using the Childhood Autism Rating Scale (CARS), which showed a higher agreement with consultants' overall diagnoses. Schopler (1985), one of its authors, recommended that individuals with Asperger Syndrome should be subsumed under "mild autism", and this classification was adopted here. Eighteen nonsymptomatic controls matched on age and sex were tested on the nonstandardised tests. Significant differences between experimental and control groups were found in all four areas. The experimental group displayed a cognitive style characterised by rigid field-independent information processing in the areas of intellectual abilities, perception, language and motor skills. Differences between "mild" and "severe autism" were statistically not significant. This may have been due to mild presentation of autistic features in the whole sample, ambiguity of classification or other reasons. However the profiles of traits and abnormalities in both groups were not as would be anticipated from an all-inclusive concept of autism with varying degrees of severity but were more in accord with Asperger's suggestion that there are qualitative differences between autism and Asperger Syndrome.