Why is your child’s vocabulary development important?

Your child’s vocabulary- what’s the big deal? Why is it important? It’s kind of amazing really as the research shows that when it comes to vocabulary, size does matter! Vocabulary means knowing and using words. It’s your child’s store of words. It provides the building blocks to language development. And vocabulary knowledge drives the development of grammar. There’s strong evidence to connect vocabulary with your child’s later language and cognitive development. Having a large vocabulary at 24 months, has been linked to stronger performance on measures of maths, reading, and behaviour at age 5. Your child’s vocabulary growth is considered to be directly related to their overall success at school. The size of your child’s vocabulary predicts her ability to learn to read.

How many words should your child know and at what ages? This is a bit like asking how long is a piece of string? Although people have been researching this area for decades, it’s still hard to find clear answers because no study is perfect and they tend to approach the topic in different ways using different methods. Let’s have a look at some ballpark figures though:

  • At 18 months, some sources say your child should say 50 words
  • Other sources say by 18 months they should say at least 24 words
  • I’ve read also read: between 43-50 verbs at 24 months with children acquiring 8 new verbs a month
  • They should be combining words by 24 months

Children of professional parents, girls, and children whose parents tend to use an encouraging style of interaction (as opposed to giving lots of commands for example) tend to have bigger expressive vocabularies. Children who had a very low birth weight or where their mothers had health problems have been found to have smaller vocabularies. One study from the 1980s found that children of professional parents would have experienced 42 million words by the time they were 4 years old! Imagine!! Their children were hearing on average 2153 words an hour. That study also found that between 86-98% of children’s vocabularies at age 3 came from their parents’ vocabularies. (Swear words any one?!!)

What if your child is learning two languages or more?

In this situation, your child is acquiring two or more vocabularies. It’s likely that they’re not going to have the same level of vocabulary in any one of their languages as a monolingual speaker of each language would have. Why? Because they’re not 2 or 3 monolinguals combined. And there are lots of factors that influence language development involved. Like how much exposure and opportunities to use the languages they get. The quality of the exposure is also important. It’s not enough to talk to them. It’s about how you talk with them. Other influences are: how alike or different the languages are (for example Spanish and Italian are closer than Spanish and Mandarin Chinese) and the statuses of the languages where you live. But still monolingual vocabulary levels tend to be the measurement benchmark which isn’t the appropriate reference point. The research that compares monolingual and multilingual children’s vocabulary size has found that multilingual children have smaller, bigger, and similar vocabularies when compared with monolingual children’s! If you test an English-only speaking child’s vocabulary, you’re testing their whole vocabulary. But if you test a multi-lingual child’s vocabulary in only one language, you’re only testing one component of their vocabulary. Not fair and not accurate. Studies which measure the total vocabulary of multilingual children have found that they’re the same size or bigger than the monolingual child’s total vocabulary. And when researchers measure what’s called conceptual vocabulary (basically number of concepts or ideas that children have a verbal label for), both groups are similar. So the bottom line is that speaking two languages or more does not disadvantage children when you measure total and/or conceptual vocabulary. Using monolingual norms to make judgements about multilingual children’s language development is a no-no. They’re not an appropriate reference point. If your child’s vocabulary is being tested maybe at school or by a speech and language therapist, make sure you keep your focus on total vocabulary. And also think about the amount of exposure to the languages.


There’s a lot of variation in the research and there are lots of studies that report smaller vocabularies for multilingual children. One study which looked at vocabulary in 1738 children between age 3 and 10 in the US found that that although the bilingual children had smaller vocabularies in both languages, the difference had to do with vocabulary associated with home environments. This isn’t an indication of a problem. Of course there was an imbalance because we use language differently according to the situation we’re using it in.  When it came to vocabulary for school, the monolingual and bilingual children were more comparable. This means that bilingual children are not at disadvantage when it came to academic performance, learning to read and write, and using spoken language for school related topics.  There’s a lovely line at the end of that paper by Ellen Bialystock and her colleagues: Bilingual children are constructing the world through two telescopes, and their two vocabularies provide the lenses.


There are several influencing factors on language development like I mentioned above. One recent study in Canada set out to control for many of these factors such as socioeconomic status, the statuses of the languages, the amount of exposure and so on. That study found a strong and systematic relationship between vocabulary development and the amount of exposure to the languages in the 5 year old children who participated. There was a clear relationship between expressive vocabulary (looking at pictures and naming them) and the amount of exposure: more exposure led to higher scores. When it came to comprehension, it wasn’t so clear. They found that once exposure hit 40-60% in either French or English, increasing exposure didn’t lead to higher scores.


It’s a complex picture but the bottom line is that multilingual children, by and large, pass through the same developmental stages in each of their languages as monolingual children do in their one language.  There are also things that are particular to multi-lingual language development too. And generally multilingual children go through the stages at roughly the same ages. It is important to remember that there’s a lot of variation in early child language development, no matter how many languages your child speaks.


So what can you do to build your child’s vocabulary?

The good news is there are lots of natural, simple ways to do this and I’ll show you how in my next post.

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Let’s get talking!


Inspired by:

Bialystock, E, Luk, G., Peets, K., and Yang, S. (2010). Receptive vocabulary differences in monolingual and bilingual children. Bilingualism 13(4):525-531.

De Houwer, A., Bornstein, M., and Putnick, D. (2014). A bilingual–monolingual comparison of young children’s vocabulary size: Evidence from comprehension and production. Applied Psycholinguistics 35 (6): 1189-1211.

Hadley, PA., Rispoli, M, and Tsu, N. (2016) Toddlers’ verb lexicon diversity and grammatical outcomes. Language, Speech, and Hearing Services in Schools 47 (1): 44-58.

Morgan, P., Farcas, G., Hillemeir, M., Hammer, C., and Maczgua, S. (2015) 24-month-old children with larger oral vocabularies display greater academic and behavioral functioning at kindergarten entry. Child Development 86(5): 1351-1370.

Rudolph, J. and Leonard, L. (2016) Early language milestones and specific language impairment. Journal of Early Intervention 38(1): 41-58.

Thordardottir, E. (2011). The relationship between bilingual exposure and vocabulary development. International Journal of Bilingualism 15(4): 426-445.



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