The persistent myth
Even in 2026 we hear families given this advice: "Speak only one language with the baby until they learn to talk". The idea behind it is that two languages "confuse" the child. The evidence, after decades of bilingual research, says the opposite.
What we know
- Bilingual children develop total vocabulary comparable to monolingual children (counting words from both languages)
- Bilingualism does not cause language delay. If there's delay, it would happen with one or two languages.
- Bilingual children often develop strengths in metalinguistic awareness and cognitive flexibility
- "Mixing" languages (code-switching) is a sign of bilingual competence, not confusion
What IS important
- **Consistent and rich exposure** to both languages — not constantly translating, but living in them
- **Differential bilingual evaluation** if there's concern — an evaluation ONLY in English may misinterpret Spanish competence as delay
- **Distinguish** between normal bilingual patterns (mixing, transfer, silent stage when changing environments) and genuine language difficulty
When to evaluate
If development in either language departs significantly from expected milestones, that warrants evaluation. If they're "just slow in Spanish" because they started English daycare, it's probably normal adaptation — but a specialist can confirm.