The relationship between child language proficiency and language of treatment on the outcomes of bilingual children with developmental language disorder

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Project Summary More than 8.5 million children in the USA speak Spanish at home (U.S. Census Table S1601, 2020) with about a half million experiencing Developmental Language Disorder (DLD), a disorder in language learning and use that cannot be attributed to limited language exposure, autism, intellectual disability, hearing impairment, etc. (Norbury et al., 2016; Tomblin et al., 1996). One key challenge in serving bilingual children with DLD is the mismatch between the language(s) they speak and the availability of Speech Language Pathologists (SLPs) who can provide services in those languages. While it seems self-evident that a monolingual child should be treated in their first language, currently there is no guidance for SLPs as to the language of intervention for bilingual children (Kohnert et al., 2005). Hence, a critical question is what language(s) of treatment will best serve children with DLD with different proficiency profiles in their development of both Spanish and English. We ask first whether gains in the treated language(s) are influenced by the child’s proficiency in each language (Aim 1). Cross-linguistic transfer has been documented in priming studies suggesting that underlying syntax representations are interconnected. Transfer effects may make it possible for a child to improve in both languages as a result of treatment in one language, provided that the child has adequate levels of knowledge to connect the information provided in treatment across both languages. The clearest evidence of transfer can be derived from assessing gains in the untreated language when treatment is presented monolingually (Aim 2). Our own preliminary data suggest that recast therapy can result in gains in both English and Spanish for children treated in just one language. In this study, we carry out a randomized controlled trial, enrolling 120 children with DLD between the ages of 4 and 6 who score below 40% correct on the use of conditional adverbial clauses (if-then) and subject relative clauses (e.g., the doll that the girl loved…). Children receive one of three possible treatments (English-only, Spanish-only, bilingual) for one grammatical structure for 9 weeks, and then outcomes are re-assessed for both structures in both languages. The second grammatical structure is then treated for 9 weeks, and outcomes are assessed a third time. Comparison of different treatment approaches will inform our understanding of what is the best approach to therapy for bilingual children with a particular proficiency profile. Comparison of gains across languages and targets will allow us to determine the role of cross-linguistic transfer in language learning and to inform theoretical accounts of language representation in the developing bilingual child.