Abstract
INTRODUCTION: One way to identify Developmental Language Disorder (DLD) is to establish clinical markers in a language to serve as reliable indicators of the disorder. This study embarks on the search for clinical markers for Vietnamese using longitudinal data from children with and without DLD. METHODS: We matched ten children previously classified with DLD to ten with typical development (TD) by age and gender. Participants completed a story generation task at three time points: kindergarten, first, and second grade. Overall grammatical development was measured using mean length of utterance, MLU, and proportion of grammatical utterances, PGU. We examined a language-specific feature, classifiers, in terms of accuracy (omission errors), diversity (number of different classifiers), and productivity, or the use of classifiers in constructions of two-to-three elements (classifier+noun, numeral+classifier+noun). Longitudinal change and group differences were examined using linear mixed modeling, supplemented by linguistic analysis. RESULTS: Both groups increased in MLU and PGU over time. The DLD group performed lower in kindergarten and continued to show lower performance over time on these measures. Classifier omission errors decreased over time with no group differences. Classifier diversity increased across groups, with lower performance by the DLD group in kindergarten and over time. For classifier productivity, TD children used classifiers in multiple constructions in kindergarten and maintained the same level over time. In contrast, children with DLD had minimal use of three-element constructions in kindergarten but increased in productivity over time. CONCLUSIONS: Children with DLD produce shorter utterances with relatively more grammatical errors compared to their TD peers in the early school years. Though no longer committing classifier omission errors, children with DLD showed more restricted use of classifiers in terms of the number of different classifiers and constructions produced. Findings inform the search for Vietnamese clinical markers of DLD.