Abstract
The present study investigated school readiness in Brazilian (Portuguese-Japanese dual language learner or DLL) 5-year-olds in Japan (1) by examining their language skills, executive function (EF), and theory of mind (ToM) in comparison to their monolingual peers and (2) by investigating the developmental relations between these three skills. DLLs scored lower than monolinguals in Japanese language skills, specifically in receptive vocabulary and the understanding of complement clauses in Japanese. DLLs and monolinguals performed similarly in EF, particularly in inhibitory control tasks measuring interference suppression and response inhibition. However, monolinguals outperformed DLLs in ToM tasks assessing false belief understanding. Finally, DLLs' interference suppression and understanding of complement clauses were both positively related to their false belief understanding. In conclusion, DLLs had school readiness difficulties in Japanese language skills and ToM, but not in EF, compared to their Japanese monolingual peers. Furthermore, the positive relationship of language and EF skills with ToM development, which is commonly reported in monolingual children, extended to an understudied population of DLLs in this study.