Breadth over depth in the semantic representations of adults with nonverbal learning disabilities

Abstract

abstractOral language in individuals with nonverbal learning disabilities (NLD) has been described as empty of meaning, despite apparently average word knowledge. The present study explored the hypothesis that depth but not breadth of semantic representations would be reduced in NLD, and that depth but not breadth would be related to nonverbal gestalt perception. A cross-sectional design compared breadth and depth of vocabulary in 50 adults with or without a diagnosis of NLD. Vocabulary results were also compared with a visual closure test. Participants with NLD had reduced vocabulary depth in comparison with controls. The NLD group also had lower scores for gestalt perception, the ability to perceive a meaningful whole from unrelated parts. Across the sample, this measure predicted scores for vocabulary depth, but not breadth. The NLD group was also less able than the Control group to estimate the size of unknown, physical features of everyday objects. Results supported clinical observations that semantic representations are unconventional and imprecise in individuals with NLD, and suggested specific cognitive underpinnings for such difficulties. Results were also compatible with separate theories of embodied and lateralized semantics. A proposal uniting these theories in a designation over elaboration model is presented.