Cognition and Social Behaviour in Adults with Asperger Syndrome

Background: In 1995, Klin and colleagues described a convergence of features in individuals with Asperger Syndrome (AS), an Autism Spectrum Disorder, and Nonverbal Learning Disability (NLD), a learning disorder defined by deficits in visual-spatial organization. The comparison was focused on the debate over whether AS is distinguishable from high-functioning autism, and subsequent research has had the same goal. With no multiple participant studies directly comparing adults with AS and NLD, the relationship between these disorders remains unclear. Behaviourally, individuals with AS and NLD demonstrate atypical social behaviour and difficulty adapting to novelty. Cognitively, they are reported to have difficulties with gestalt perception, or the perceptual integration of constituent parts to make a meaningful whole.

Objectives: This study explored commonalities in and differences between perceptual processes in adults with AS and NLD. The primary goal was to determine whether individuals with AS and NLD share underlying perceptual integration deficits that a) distinguish them from typical adults, b) impair their ability to communicate in social situations, and c) are evident regardless of whether they are manipulating verbal or nonverbal material. A second goal was to determine whether deficits in perceptual processes differ by degree or kind in individuals with AS and NLD.

Methods: A sample of typical adults was compared to adults with a community diagnosis of AS or NLD on social and gestalt perception tests. Their performance was compared on a verbal test of social behaviour interpretation (Dewey, 1991), and two types of nonverbal tests. The first set of nonverbal tests necessitated gestalt integration for successful completion; that is, they could not be solved using fragments. This set included puzzle assembly, figure copying, and two gestalt closure tasks. The second set of nonverbal tests could be solved using either a step-by-step approach or gestalt integration. This set included embedded figures, matrix reasoning, and two versions of a block design task.

Results: Participants with AS or NLD had lower scores on tests of perceptual integration and social behaviour interpretation than comparison participants. The deficit appeared to extend beyond test format, with lowered scores evident on both nonverbal tests of gestalt perception and verbal tests of social behaviour interpretation. Moreover, there was a trend for members of both clinical groups to score more poorly on tests that demand gestalt perception than on tests that can also be solved correctly with an analytic approach. Typical participants did not show this pattern, and the trend was more apparent for those with AS than NLD.

Conclusions: Results suggested that adults with AS and NLD may be distinguished from typical adults using tests of gestalt integration. Adults with AS appeared to compensate better than those with NLD on nonverbal tests that can be solved analytically. Both clinical groups had difficulty with tasks that required gestalt perception, including social behaviour intepretation. Differences in scores for nonverbal tests of gestalt integration suggest that with careful consideration of the degree to which such tests may be solved analytically, the disorders may be distinguished from each other.