Immersion in dual-language programs does not impede children's native language processing.

The benefits of dual-language immersion (DLI) versus English-only classrooms for minority-language speakers' acquisition of English have been well documented. However, less is known about the effect(s) of DLI on majority-language speakers' native English skills. Prior studies largely used accuracy-focused measures to index children's language skills; it is possible that processing-based tasks are more sensitive to the effects of DLI experience. Thirty-three monolingual native English-speaking children attending English-only classrooms and thirty-three English-speaking children attending English-Spanish DLI matched in age, gender, nonverbal IQ, and socio-economic status were tested twice, 1 year apart, on standardized and processing-based measures of English vocabulary and morphosyntax. We ran linear mixed-effects models to examine the extent to which group and time would predict scores on knowledge-based measures of vocabulary and morphosyntactic knowledge, as well as accuracy and reaction times on processing-based measures of English vocabulary and morphosyntax. Results revealed comparable levels of growth in English for both groups. A subtle effect of DLI was observed on a lexical-decision task: bilinguals were slower in Year 1 but both groups were equally efficient in Year 2. These results indicate that DLI programs have minimal impact on majority-language speakers' native-language skills in the age-range tested. This study is the first to longitudinally examine processing-based native language outcomes in bilingual children in DLI classrooms. We do not find evidence that DLI exposure carries a cost to native language development, even when indexed by processing measures. This should reassure parents, educators, and policymakers in that there are no downsides to DLI.

Déclaration de conflit d'intérêts

Declaration of conflicting interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.