Semantic Integration in Adults with Asperger Syndrome and Nonverbal LD

Background:

The striking combination of verbal strengths and adaptational weaknesses characteristic of Asperger Syndrome (AS) has also been described as typical of Nonverbal Learning Disability (NLD), a learning disability subtype. Only recently has research begun to explore similarities between AS and NLD, and none of this research has investigated language. The present study addressed this gap.

Empirically, adults with AS and with NLD have demonstrated average or better vocabulary on standardized testing. Some studies, however, have reported semantic weaknesses, the sources of which are unknown. The present study examined the possibility that semantic difficulties arise during the integration of unique semantic representations. Semantic integration involves the detection and elaboration of overlap between discrete representations to form a novel, higher-order relationship. As such, it is a form of gestalt perception – a relational process in which meaningful wholes are constructed from stimulus fragments that differ qualitatively from the larger whole. Low scores on nonverbal tests of gestalt perception have been reported in AS and NLD, as has difficulty understanding verbal gestalts such as metaphors.

Objectives:

We tested the hypotheses that: a) adults with AS and NLD have at least average scores on standardized vocabulary tests, b) adults with AS and NLD share a deficit in integrative processing, and c) the processing deficit affects the apprehension of both verbal and nonverbal gestalts.

Methods:

Typical adults were compared to adults with a community diagnosis of AS or NLD on measures of vocabulary, semantic integration, and nonverbal gestalt perception. The measures of semantic integration included remote associate problems (Swiss, cottage, cake = cheese), similarities (how are two objects or concepts alike?), and metaphor identification. The nonverbal tasks included puzzle assembly and two tests of gestalt closure.

Results:

1) The groups did not significantly differ on vocabulary measures. 2) The clinical groups had significantly lower scores on verbal and nonverbal integration measures than controls. 3) Verbal tests of semantic integration and nonverbal measures of gestalt perception were significantly positively correlated across the sample. The same pattern was not true for vocabulary and semantic integration tests, or vocabulary and nonverbal gestalt perception.

Conclusions:

Adults with AS and NLD demonstrated similar vocabulary levels to typical adults, yet had low scores for verbal tests that required integration of unique semantic representations. Results could not be explained by differences in single word knowledge, and supported the hypothesis that adults with AS and NLD experience difficulty with integrating discrete word meanings into novel semantic representations. Results also supported the hypothesis that verbal semantic integration and nonverbal gestalt perception rely on the same underlying cognitive function; low scores for the latter corresponded with low scores for the former. Gestalt cognitive functioning appears to distinguish adults with AS and with NLD from their typical peers at both verbal and nonverbal levels of inquiry.