Language impaired children's grammatical sensitivity in a dual task

Previous studies have shown that English speaking children with language impairment (LI) have more difficulty with verbal inflections than with noun inflections. Competing theories of language impairment offer opposing explanations for this difference in language performance. The purpose of this study was to test predictions of these theories on children with LI and normally developing children at ages 8--13 years in an online processing task. The predictions tested included effects of acoustic salience, agreement features, and information processing capacity. The homophonous regular third person singular verb inflection and the regular noun plural inflection were chosen for the study to control for phonetic characteristics. The position of these inflections in the sentence was varied between medial or final position to test whether the processing demands of sentence final lengthening or build-up of sentential information affected children's sensitivity to these inflections. A cross modal dual task was used to create a sensitive measure for children's reactions to the absence or presence of these inflections. The children listened to sentences containing obligatory contexts for the inflections and responded to an unrelated secondary visual task synchronized with the beginning of the obligatory context. Increased reaction time to the visual stimulus was interpreted as interference caused by increased processing load.; The analyses of data from 3-way ANOVA (group x category x position) indicated results in a similar pattern for children with LI and their controls for both grammatical and ungrammatical data. The results did not indicate any effects of category that would differentiate performance on verbal inflections from noun inflections. The effects of position indicated that both children with LI and normally developing children experienced more interference in sentence medial position than sentence final position, however, children with LI experienced significantly more interference. These results were interpreted as evidence that older school-age children with LI differ from their same age peers in general sentence processing capacity rather than sensitivity to specific inflections.