Does a second language delay a child’s speech?

Bilingualism is not a cause of language disorder

Babies raised with two languages from birth babble at the same age, say their first words at about the same age, and start combining words at about the same age as babies raised with one.¹ A study that followed bilingual infants — including children learning a signed and a spoken language at once — found first words and first two-word combinations landing in the same windows as the monolingual norms, in both languages.¹ Two languages do not take turns in a child’s head; they grow side by side.

Where the myth comes from

Count a bilingual two-year-old’s words in only one of their languages and you will often get a smaller number than a monolingual child’s. That is real, and it is the whole basis of the worry. But a child who hears Spanish at home and English at daycare knows leche and milk, zapato and shoe — and also words that exist only in one setting: the daycare’s circle time, the grandmother’s abuelita. Those are different measures: total vocabulary adds word forms across languages; conceptual vocabulary counts a shared meaning once. In one study of Spanish–English toddlers aged 22 to 30 months, total vocabulary was comparable to the monolingual group; conceptual vocabulary was smaller.³ Neither calculation alone can rule out a language difficulty.

Three things that are true about bilingual vocabularies

1. Input is split, so each language grows with its share

A child who hears a language 30% of the time will, for a while, know fewer words in it than a child who hears it 100% of the time. The size of a bilingual toddler’s vocabulary in each language tracks how much of that language they hear.^{2, 4} Exposure matters, but it does not produce a fixed word total or explain away every concern.

2. Mixing is a skill, not confusion

Bilingual toddlers put words from both languages in one sentence — “more leche”, “quiero ball”. This is code-mixing, bilingual adults do it too, and children do it according to the grammar of the languages involved and according to who they are talking to.⁵ A two-year-old who says “agua please” to a grandparent and “water please” at daycare is not muddled. They are choosing.

3. A delay, when there is one, is not caused by the second language

Children with genuine language disorders can and do become bilingual, and there is no evidence that dropping a language helps them; the professional guidance is to support both.⁶ If a bilingual child needs speech therapy, the therapy should account for both languages — and the family’s home language should stay.

What to tell the doctor

If a pediatrician or a relative suggests dropping a language to “help” a late-talking toddler, three sentences cover it:

• Bilingualism does not cause a language disorder; children still vary in their development.⁸
• Vocabulary should be counted across both languages; that is the standard in the research.³
• If there is a real delay, the guidance from speech-language professionals is to evaluate in both languages and keep both.⁶

Then keep the word list. Write down spoken words and meaningful sound approximations in each language, and record signs and gestures separately. Give the evaluator examples and explain how much your child uses each language. The late-talker guide explains what word counts can and cannot tell you, the signs worth a call, and how to ask for an assessment.

What helps a bilingual toddler

The same things that help any toddler, in each language: a real person, naming what the child is looking at, in the moment.⁷ If the minority language is the one that gets fewer minutes, give it the routines — bath, bedtime, breakfast — so there are regular chances to talk together. If you use our cards, the useful trick is the language switch on the card: the same picture can be milk at breakfast and leche at dinner, as an example you can talk about together. The bilingual toddler guide goes through the research on how, household by household.