Bilingual Language Development: Myths and Facts Part I
Today, many parents want to raise proficient, bilingual children and come to speech-language pathologists, doctors, and other professionals with many questions. In Toronto, up to 50% of students speak a native language other than English, and worldwide, it is estimated that the number of bilingual children is equal to the number of monolingual children.  Still, up until recently some doctors and other professionals recommended against exposing children to two languages because of older attitudes that are not scientifically based. When children have communication disorders or delays, discerning myth from fact becomes even more confusing. This is the first section of a two-part article that discusses the evidence behind some common notions related to bilingual language development and aims to help you to navigate this under-researched topic.
- Being bilingual means that you speak two languages equally well, that you have a perfect knowledge of both languages, and that you speak both with no accent.
This is rarely the case, and most bilinguals will be dominant in one language, even when they learned both from birth. Therefore, there is no set level of proficiency in a language that an individual must attain in order to be considered “bilingual”. A person’s skills in each language may fluctuate over time depending on their opportunities to use the language.
- Bilingual children start speaking later than monolinguals.
Monolingual and bilingual children say their first words at approximately the same age, and bilingual children are no more likely than monolingual children to have a language delay or disorder.  The idea that bilingualism leads to language delay was popular around the middle of the 20th century and may have been developed because language delay in any child can be difficult to explain. In the case of bilingual children, some parents and professionals may jump to the conclusion that the delay was caused by learning two languages.  Bilingual children with language delay will show a delay in both of their languages, similar to the delay that monolingual children show in their one language.
- Learning two languages will confuse a child, especially children with language delays. Children with language delays will always mix their languages together. Parents should avoid mixing languages together when they speak.
Children have the ability to tell languages apart from a very early age. In fact, infants and young children are very sensitive to the differences between languages (especially the language’s rhythm). 
Mixing languages within the same sentence is called “code switching” and is a normal part of language development.  Bilingual adults will code-switch in order to convey nuanced meanings that are specific to words and phrases in both of their languages, while young children code-switch because they have limited vocabularies. Code-switching in young children is actually quite clever; if children know that their conversational partner speaks both languages, they will use their limited vocabulary in each language in order to get their message across. As young children grow their language skills, their code-switching will decrease. Even 2-year-olds have been shown to use the appropriate language depending on their conversational partner. 
The jury is still out on whether it is ok for parents to mix two languages together when they speak to their children, as there is little research in this area. It has been suggested that mixing two languages together may make early language learning more difficult, but that it also may later lead to cognitive benefits. 
Stay tuned for some more myths and facts in our next edition!
 Byers-Heinlein, K., Burns, T. C., & Werker, J. F. (2010). The roots of bilingualism in newborns. Psychological Science, 21(3), 343–348.
 Byers-Heinlein, K., Lew-Williams, C. (2013). Bilingualism in the early years: What science says. LEARNing Landscapes, 7 (1), 95-112.
 Byers-Heinlein, K. (2013). Parental language mixing: Its measurement and the relation of mixed input to young bilingual children’s vocabulary size. Bilingualism: Language and Cognition, 16(01), 32– 48.
 Canadian Council on Learning. (2008). Understanding the academic trajectories of ESL students. Retrieved from http://www. ccl-cca.ca/pdfs/LessonsInLearning/Oct-02- 08-Understanding-the-acedemic.pdf
 Paradis, J., Crago, M., Genesee, F., & Rice, M. (2003). Bilingual children with specific language impairment: How do they compare with their monolingual peers? Journal of Speech, Language, and Hearing Research, 46, 1–15.
 Place, S., & Hoff, E. (2011). Properties of dual language exposure that influence two- year-olds’ bilingual proficiency. Child Development, 82(6), 1834–1849.