Studies have shown that young children who are bilingual have smaller number of vocabularies in one language (e.g. English) compare to other children who only speaks one language. However, if you combine the number of vocabularies across from the two languages (e.g. # of vacabs in English + in Chinese), there is no difference between the kids in terms of the number of vocabularies. I think they also found that kids do equally well aspects of the language but I'll need to go back and check on that (if anyone's interested). So if anyone's interested in me posting the information with the study let me know.