Clinical markers of DLD in bilingual and monolingual Vietnamese children - PROJECT SUMMARY Developmental language disorder (DLD: 7% prevalence), defined by low language despite otherwise normal development, puts children at greater risk for reading problems and lower vocational attainment. There exist language-based disparities in the identification of DLD. Bilingual children are more likely over- or under-identified with DLD (Samson & Lesaux, 2009): Under-identification delays access to intervention, while over-identification misappropriates already scarce resources. DLD identification is particularly challenging during the initial school years, when many bilinguals are in the processing of learning English as a second language. Assessing children’s first language substantially improves diagnostic accuracy. The proposed project focuses on Vietnamese, an understudied yet widely spoken language (1.5 million in the US, 100 million worldwide). Vietnamese is highly distinct from English: Finding common clinical markers across contrastive languages contributes to theoretical accounts of underlying mechanisms of the disorder. Our research team has the expertise and local and global partnerships to search for clinical markers of DLD in Vietnamese. We have pioneered the study of DLD in Vietnam by establishing a multi-method classification system for DLD in kindergarten and by measuring language-reading development from kindergarten through second grade. In the US, we have defined parameters for typical development (TD) in Vietnamese bilinguals in the early school years. The proposed study will recruit Vietnamese-speaking children, ages 4-6 years, in the US (bilingual TD=100, DLD=25) and Vietnam (monolingual TD=160, DLD=40). Central hypothesis: There are Vietnamese clinical markers that will confirm the presence or absence of DLD at the individual level, whether children are learning Vietnamese alone or in combination with English. Aim 1 establishes the diagnostic accuracy of nonword repetition and sentence repetition for Vietnamese monolinguals. We extend our prior work on these tasks to a younger age (include 4yo) and a larger DLD sample. Aim 2 systematically compares four groups (N=80, 20/group) of bilinguals (TD, DLD) and monolinguals (TD, DLD) matched by age, gender, and maternal education, to capture emerging skills that can serve as grammatical markers of Vietnamese DLD. Aim 3 calculates the diagnostic accuracy of all clinical markers - grammar (accuracy, diversity, productivity), sentence repetition, and nonword repetition- for bilinguals (n=125), monolinguals (n=200), and combined total sample (N=325), which will serve as the most rigorous test of diagnostic accuracy. Impact: This project will help to transform clinical language assessment procedures to serve our increasingly diverse society. Tools produced from this project will improve diagnostic accuracy for Vietnamese-speaking children in the US and worldwide, particularly Vietnamese-speaking children in the US who start school with minimal English proficiency, for whom accurate identification heavily relies on first language skills. This study can serve as a model for other Asian tonal languages that in combination with Vietnamese comprise 6.5 million speakers in the US.
