Description
The rapid growth in multilingual speakers in United States has aroused attention to the development of this population, especially Spanish-English bilingual children. Despite controversy on enhanced executive function (EF) ability for bilingual speakers, recent research shows that this advantage emerges early and depends upon translation equivalents (TEs), which indicate the words with same referential meanings across languages. However, the early development of this advantage needs more exploration. First, the earliest age at which Spanish-English bilingual children have been tested previously was 6 years of age. Second, in 30-month-old French-English bilinguals, larger increase in TEs predicts better performance on set-shifting tasks. For this reason, TEs might index daily inhibitory practice. Another potential index, code-switching (CS) refers to the alternation between two languages while speaking. Whether CS also indexes inhibitory practice remains unknown. In sum, we are interested in how early this cognitive benefit emerges in Spanish-English bilingual toddlers and whether the acquisition of TEs or CS relates to early EF. The final sample included 59 monolingual English and 32 Spanish-English bilingual children. For monolinguals, the average exposure to English was 98.6%, and for bilinguals, the average exposure to their dominant language was 60.7%. Participants visited the lab at 23 and 30 months of age. The caregivers completed the MacArthur-Bates Communicative Development Inventory: Words and Sentences: an established parent-report measure of expressive vocabulary. At 30 months of age, four EF tasks (Multilocation, Reverse Categorization, Shape Stroop, Gift Delay) were administered in children's dominant language. Additionally, we recorded two free-play sessions, one in each language, in which the parent and the child played for 20 minutes. After controlling for SES, no performance difference was revealed across groups, in either EF task. However, after controlling for growth in Total Conceptual Vocabulary, growth in TEs significantly correlated with performance on the Stroop task. Also, CS from dominant to non-dominant language negatively correlated with performance on set-shifting tasks suggesting that CS does not index inhibitory practice. The present study supports the critical role that the TE acquisition plays in establishing this cognitive benefit and is the first to explore the relation between CS and EF.
