Language intervention in bilingual children with developmental language disorder: A systematic review

BACKGROUND: Although there is a growing body of literature on cognitive and language processing in bilingual children with developmental language disorder (DLD), there is a major gap in the evidence for language intervention. Critically, speech-language therapists are often required to make clinical decisions for language intervention on specific domains, such as phonology, vocabulary, morphosyntax and literacy. AIMS: To examine evidence for language intervention and cross-language transfer effects in bilingual children with DLD. Specifically, the study aimed to review intervention evidence targeting non-linguistic cognitive skills and six areas of language: phonology, vocabulary, morphosyntax, pragmatics, narrative skills and literacy. METHODS & PROCEDURES: We carried out searches in five electronic databases: CINAHL, Scopus, Psychinfo, Proquest and Sciencedirect. Data from selected papers were extracted and organized into the three following categories: study information, participant information and intervention information. Critical appraisal for selected papers was conducted using a quality assessment tool (QAT). OUTCOMES & RESULTS: We included 14 papers in the review. The majority indicated evidence for vocabulary intervention. There was limited evidence for intervention targeting phonology or morphosyntax. Cross-language generalization effects were evident for vocabulary, but in some instances also reported for morphosyntax and literacy. CONCLUSIONS & IMPLICATIONS: The present review indicates that there is a significant gap in the literature regarding language intervention for several key language areas such as morphosyntax, narrative skills and literacy. There are only limited data for the effects of cross-language generalization indicating that more research is needed in this area specifically for skills beyond vocabulary. WHAT THIS PAPER ADDS: What is already known on the subject Previous studies have examined the effects of bi- and monolingual intervention in bilingual children with DLD. Although the results indicated superior effects for bilingual compared with monolingual intervention, language intervention evidence in specific language domains (e.g., vocabulary, literacy) has not been investigated. What this paper adds to existing knowledge This study will add intervention evidence specific to language domains such as phonology, vocabulary, morphosyntax, pragmatics, narrative skills and literacy. Additionally, we have synthesized intervention evidence on non-linguistic cognition given that these skills are often impaired in bilingual children with DLD. The review has also demonstrated evidence for the effects of cross-language transfer beyond vocabulary skills, especially when the intervention was provided in the home language. What are the potential or actual clinical implications of this work? Although there was a lack of intervention evidence in language domains such as pragmatics, the results indicated some evidence for intervention targeting vocabulary. However, positive effects of cross-language generalization were not constrained to vocabulary but were also reported for intervention targeting mean length of utterance and literacy in the home language. This result indicates an interactive nature of the two languages, as well as provides further evidence for supporting home language(s) in intervention. Finally, intervention targeting non-linguistic cognition may yield additional cross-domain generalization to language skills specifically for bilingual children with DLD.