Look at the gato! Code-switching in speech to toddlers.

We examined code-switching (CS) in the speech of twenty-four bilingual caregivers when speaking with their 18- to 24-month-old children. All parents CS at least once in a short play session, and some code-switched quite often (over 1/3 of utterances). This CS included both inter-sentential and intra-sentential switches, suggesting that at least some children are frequently exposed to mixed-language sentences. However, we found no evidence that this exposure to CS had any detrimental effect on children's word learning: children's overall vocabulary size did not relate to parental inter-sentential CS behavior, and was positively related to within-sentence CS. Parents often repeated words across their two languages, but this did not appear to increase the likelihood of children having translation equivalents in their vocabulary. In short, parents appear to CS fairly often to young children, even within sentences, but there is no evidence that this delays child lexical acquisition.