New to this topic? Start with our companion article: Bilingual Language Learning: Busting the Myths | Brisbane Speech Pathologist
More than one in five Australians speak a language other than English at home (Australian Bureau of Statistics, 2022). Across Brisbane's culturally and linguistically diverse (CALD) communities, many children are growing up hearing two, three, or sometimes more languages every day. First Nations children may be navigating traditional languages, Aboriginal English, Kriol, and Standard Australian English — every one of those is a meaningful part of the child's linguistic identity, and the research in this article applies to them too.
This article is the research home base for our bilingual series. If our myth-busting companion covers what's not true, this one covers what the evidence actually tells us about how bilingual and multilingual children develop language — and when it's worth getting professional support.
The Cognitive Benefits of Bilingualism
One of the most exciting areas of bilingual and multilingual research is around cognitive benefits. Bialystok (2018) has spent decades studying how bilingualism affects the brain, and the findings are impressive. Children who grow up with two or more languages often show advantages in:
- Executive function — the ability to plan, pay attention, switch between tasks, and manage competing information. Bilingual children practise this constantly because their brains are always managing two language systems.
- Metalinguistic awareness — an understanding of how language works. Bilingual children often develop an earlier awareness that words are arbitrary labels for things, which can support early literacy.
- Cognitive flexibility — the ability to think about things in more than one way and to adapt to new information.
These aren't small effects. Bilingualism gives children's brains a genuine workout, and the benefits extend well beyond language.
What Typical Bilingual Development Looks Like
Bilingual development doesn't look exactly like monolingual development, and that's perfectly normal. Here are some of the patterns you might notice:
Code-Switching Is Normal and Healthy
If your child mixes languages within a sentence — starting in English and finishing in Mandarin, or dropping a Vietnamese word into an otherwise English sentence — that's called code-switching, and it's completely typical. Bilingual adults do it all the time. It's not a sign of confusion; it's a sign that your child is a flexible communicator who uses all the language tools available to them.
Vocabulary Is Distributed Across Languages
This is an important one. Bilingual children often know some words in one language and different words in the other. A child might know all their food words in their home language (because that's the language used at mealtimes) and all their classroom words in English (because that's the language of school).
This means that if you test a bilingual child's vocabulary in English only, you'll likely underestimate what they actually know. Core, Hoff, Rumiche, and Señor (2013) demonstrated that when researchers measured children's total conceptual vocabulary — counting a concept as known if the child could name it in either language — bilingual children's vocabulary was comparable to that of monolingual children.
One Language May Be Stronger Than the Other
It's very common for bilingual children to have a dominant language — one that's stronger than the other. This often shifts over time. A child might be dominant in their home language before starting school, then shift towards English as they get more exposure at school. This is normal and expected. The balance between languages reflects the amount and type of input a child gets in each one.
Language Milestones Follow a Similar Timeline
Research by Paradis, Genesee, and Crago (2021) confirms that bilingual children reach major language milestones — babbling, first words, combining words, developing grammar — within the same broad timeframes as monolingual children. Bilingualism itself does not cause delay.
Understanding Total Conceptual Vocabulary
This concept is so important that it's worth spending a bit more time on it. When we assess a bilingual child's language, looking at just one language gives us an incomplete picture — like judging a book by reading only half the chapters.
Imagine a child who knows 200 words in English and 150 words in Vietnamese, with 80 of those words overlapping (known in both languages). Their total conceptual vocabulary is 270 unique concepts — well within the typical range for their age. But if we only counted their English words, we'd see 200 and might worry they were falling behind.
This is why it's essential that any language assessment for a bilingual child considers both languages. At Speaking Speech Pathology, we always take a whole-child, whole-language approach.
When Might a Bilingual Child Need Speech Pathology Support?
Bilingualism and multilingualism don't cause language difficulties, but bilingual and multilingual children can still experience them — just like monolingual children can. The key question is whether the difficulty shows up across all of a child's languages, not just one.
Here are some signs that it might be worth having a chat with a speech pathologist:
- Late talking in both languages. If your child isn't using words by 18 months or combining words by 2–2.5 years in either language.
- Difficulty being understood in both languages. If family members who speak each language are finding it hard to understand your child, this could suggest a speech sound difficulty rather than a bilingual difference. (Our article on bilingual children and speech sounds unpacks what's typical and what's not.)
- Struggling to follow instructions in both languages. If your child has trouble understanding what's said to them — not just in English, but also in the home language.
The important thing to remember is that a difficulty caused by a language difference will only show up in one language, while a true language difficulty will show up across both. Some of the bilingual children I've worked with who did have a language difficulty were showing the same pattern in every language they spoke — and that's usually the clearest signal that something beyond bilingualism is going on.
What Assessment Should Look Like
A good bilingual language assessment will gather detailed information about which languages your child hears and uses (and in what contexts), consider your child's skills in both languages with input from family members or interpreters, and look at total conceptual vocabulary and overall communication rather than relying on monolingual English norms alone.
You're Doing a Great Thing
If you're raising your child with two, three, or more languages, you're giving them an incredible gift — one that benefits their brain, their identity, their relationships, and their future. The research is clear: bilingualism and multilingualism are advantages, not barriers.
Alexandra Bouwmeester is a Senior Speech Pathologist (MSPA, CPSP) with over 14 years' experience supporting bilingual and multilingual families. She offers mobile speech pathology to families across Brisbane's south side and Logan.
If you have any questions about your bilingual child's language development, we're here to help. Get in touch with Speaking Speech Pathology — we love working with multilingual families and making sure every child's full language profile is understood and celebrated.
References
Bialystok, E. (2018). Bilingual education for young children: Review of the effects and consequences. International Journal of Bilingual Education and Bilingualism, 21(6), 666–679.
Core, C., Hoff, E., Rumiche, R., & Señor, M. (2013). Total and conceptual vocabulary in Spanish–English bilinguals from 22 to 30 months: Implications for assessment. Journal of Speech, Language, and Hearing Research, 56(5), 1637–1649.
Paradis, J., Genesee, F., & Crago, M. B. (2021). Dual Language Development and Disorders: A Handbook on Bilingualism and Second Language Learning (3rd ed.). Paul H. Brookes Publishing.
