Taxonomic knowledge in children with intellectual and/or developmental disabilities who use augmentative or alternative communication

This study is a first step towards informing processes of vocabulary development, specifically at the level of lexical integration, in children with intellectual and developmental disabilities (IDD) who use augmentative or alternative communication (AAC). Experiment 1 included 18 children with IDD who use AAC and 18 age-matched peers. Participants completed a receptive categorization task at three taxonomic levels: superordinate (e.g., animal), basic (e.g., dog), and subordinate (e.g., German Shepard). Results revealed differences in performance between groups; results also revealed that the AAC group followed a developmentally expected pattern. Experiment 2 compared the performance of 18 children who use AAC and 17 vocabulary-matched peers on the same task. Results revealed that groups performed similarly at the superordinate level and differently at the basic and subordinate levels. Experiment 3 compared the performance of two subsets of children who use AAC on the same task: IQ at or above 70 and IQ below 70 (both n = 9). An added comparison group included 6 children with an intellectual disability who speak as IQ-matched peers. Although results were not significant, effect sizes were medium to large, suggesting potential group differences in a fully powered study that could reveal taxonomic benefits from AAC use. Taken together, results from this early study suggest that children who use AAC present with differences in taxonomic knowledge than their speaking peers. These early findings will guide future investigations into vocabulary development and lexical integration in children who use AAC, ultimately aiming to inform early vocabulary selection.