Spoken Language Processing as an Early Marker of Language Impairment in Bilingual Children

Developmental language disorder (DLD) affects 6-8% of children and has long-term impacts on education, health, and well-being. Early identification of children at risk for DLD is critical to improving long-term outcomes. However, for the large number of bilingual children in the US, early signs of DLD frequently go unrecognized. A key challenge in identifying bilingual toddlers at risk for DLD is that current measures cannot differentiate between transient delays in accumulated language knowledge – which can result from reduced exposure to each language – and “true” impairments in language learning and processing that are likely to result in persistent problems. Measures of language processing offer a promising approach to identifying DLD in bilingual populations. These tasks aim to tap into the underlying deficits of DLD while being less dependent on language knowledge. This study proposes to use fine-grained measures of spoken language processing to compare the performance of Spanish-English bilingual toddlers with low expressive vocabularies (“late talkers”, n=40) and typical expressive vocabularies (“typically developing”, n=40) on two language processing tasks: (1) familiar word recognition and (2) novel word learning, and to examine associations between processing and vocabulary over the third year of life. Children’s efficiency in processing familiar (Aim 1) and novel words (Aim 2) in Spanish and English will be assessed in the looking-while-listening (LWL) task at 24 and 30 months. Speed and accuracy of language processing will be used to predict trajectories of total vocabulary growth from 24 to 36 months (measured via parent report) and standardized scores on a bilingual test of conceptual vocabulary at age 3 (Aim 3). This represents the first investigation of the language processing skills of bilingual late talkers relative to their typically developing peers, and of the extent to which these skills predict lexical development. Completion of study aims will inform the development of diagnostic methods for early identification of DLD in bilinguals and will advance theoretical understandings of the mechanisms underlying language impairments more generally.