1 Concordia University, Department of Psychology, Montreal, Canada.
2 Princeton University, Department of Psychology, Princeton, USA.

Language mixing is common in bilingual children's learning environments. Here, we investigated effects of language mixing on children's learning of new words. We tested two groups of 3-year-old bilinguals: French-English (Experiment 1) and Spanish-English (Experiment 2). Children were taught two novel words, one in single-language sentences ("Look! Do you see the dog on the teelo?") and one in mixed-language sentences with a mid-sentence language switch ("Look! Do you see the chien/perro on the walem?"). During the learning phase, children correctly identified novel targets when hearing both single-language and mixed-language sentences. However, at test, French-English bilinguals did not successfully recognize the word encountered in mixed-language sentences. Spanish-English bilinguals failed to recognize either word, which underscores the importance of examining multiple bilingual populations. This research suggests that language mixing may sometimes hinder children's encoding of novel words that occur downstream, but leaves open several possible underlying mechanisms.