Question:  My 4 YO child has a habit of mixing both English and Chinese in a sentence, will it affect his language abilities? what should I do to help him?

Answer:
What your 4-year old does is called code switching or language mixing and this is common in children who know more than one language. Actually your child is doing something amazing as he is able to switch between English and Chinese using the vocabulary and/or the correct grammar!  Current research also shows that engaging in code switching is a reflection of a child’s cognitive and communicative ability.
 
I believe it will not affect your child’s language abilities but eventually we do want him to work towards using one language to communicate at any one time. You can help with this by first observing his language skills and listening in order to understand his range of vocabulary. With that, you will be able to gauge better whether or not he has acquired enough vocabulary to use. You can extend his learning by playing word games that will increase his repertoire of vocabulary in that language. 
You can help support his learning by being a strong language model. In this case, it means when you speak to others, keep to using one language, for example English, intentionally. Even if your child code switches while communicating with you, continue to communicate in one language consistently.
 
Avoid correcting your child when he code switches as that may send the wrong message that his language competency is being devalued. Instead, you can support him by focusing on extending his conversation using one language. The aim is to support him in his language acquisition by encouraging him to continue asking his questions or giving his comments. Listen to what he is trying to say and focus on building on his ideas and information by getting him to talk about what is important to him.
 
You can also arrange play dates for him by intentionally setting him up with children who are strong in speaking one language. An example would be if you know of any children who are competent Mandarin speakers, then set up a play date with them so that your child acquires the language by learning the grammar and vocabulary from them.

The Expert:

Iris Lim
Principal 
Chiltern House