Bilingual infants process mixed sentences differently in their two languages

In bilingual language environments, children learn two languages in the same amount of time that monolingual children learn one, and children do not learn their two languages at exactly the same rate. Furthermore, learning two languages requires children to deal with challenges not found in monolingual input, notably the use of two languages within one utterance (Do you like the perro?/¿Te gusta el doggy?). For bilinguals of all ages, switching between languages can impede processing efficiency. But are all switches equally challenging? We tested Spanish-English bilingual toddlers' processing of single-language and mixed-language sentences in both languages. We found asymmetrical switch costs when toddlers were tested in their dominant vs. non-dominant language, and toddlers benefited from hearing nouns produced in their dominant language. These results suggest an important commonality between monolingualism and bilingualism: when toddlers have more robust representations of a particular item, they can better recognize it in diverse contexts.