The bilingual speech delay myth: what the research actually says

Last updated 2026-07-09

Bilingualism does not cause speech delay, and a child growing up in a two-language home is not at higher risk for a true language disorder. This is one of the most stubborn myths in early childhood development, and it has led generations of parents to drop a language, switch to English only, or wait and see because "bilingual kids take longer." None of that holds up against the evidence.

The American Speech-Language-Hearing Association (ASHA) states it plainly: "Being bilingual or multilingual does not cause speech, language, or communication disorders." ^[1] The American Academy of Pediatrics (AAP) agrees, and its 2017 policy statement on dual language learners affirms that children raised in bilingual households reach communicative milestones at the same rate as monolingual peers. ^[2]

So where did the myth come from? Partly from a misreading of early vocabulary data. When researchers measured vocabulary in only one of a bilingual child's languages, those kids looked like they had smaller word banks. They did, in that one language. But add up what the child knows across both languages and the total sits right in line with monolingual norms. Researchers call this "conceptual vocabulary" counting, and it's the only fair way to judge a bilingual child's word learning. ^[3]

If your child is late to talk and is also being raised bilingual, the bilingualism is almost certainly not the cause. Something else is worth looking at.

What bilingual milestones actually look like

The core milestones are identical. A bilingual child should babble by 6 months, say first words by 12 months, combine two words by 24 months, and produce sentences by 36 months, just like a monolingual child. ^[2] Two languages in the home don't shift the timeline.

A few things do look different, though. Bilingual children mix their two languages within the same sentence, and this code-switching isn't confusion or a sign of disorder: it's sophisticated linguistic behavior, and even children as young as 2 do it in ways that follow grammatical rules. ^[4] Vocabulary counted in a single language also looks smaller than it really is. Count only the Spanish words, and a Spanish-English bilingual child may seem to know fewer words than a monolingual Spanish speaker the same age. That's expected. The right measure is total vocabulary across both languages. And the dominant language can shift fast: a child who starts preschool in English may become English-dominant quickly even when Spanish was the home language from birth, and that shift isn't a red flag by itself. None of these patterns point to delay. They point to typical bilingual development. The longitudinal work by Pearson and colleagues found that bilingual children's total vocabulary growth curves tracked monolingual growth curves closely when measured the right way. ^[3]

What the research says about bilingualism and language disorders

Developmental language disorder (DLD) shows up in bilingual children at roughly the same rate as in monolingual children, about 7 percent of the child population. ^[5] Being bilingual neither shields a child from language disorders nor makes them more likely.

A 2011 review published in the Journal of Speech, Language, and Hearing Research analyzed studies covering thousands of children and found no credible evidence that bilingualism raises the risk of language impairment. ^[6] A frequently cited meta-analysis by Cummins established the "threshold hypothesis," which actually suggests that high bilingual proficiency may bring cognitive advantages, not disadvantages. ^[7]

The harder problem is identification. Bilingual children with genuine language disorders get missed or misclassified all the time. Clinicians sometimes chalk up real symptoms to the bilingualism, which delays the child's access to early intervention. The reverse happens too: some bilingual children get referred for evaluation because a monolingual clinician doesn't recognize typical bilingual patterns, and they end up over-identified. Both errors are common.

The fix is an evaluation by a speech-language pathologist experienced with bilingual children, ideally one who can assess the child in both languages. ASHA maintains a directory of certified clinicians. ^[1] If you can't find a bilingual SLP nearby, online speech therapy has grown a lot, and there are now bilingual providers working across languages and time zones.

Should you switch to one language to help your child talk faster?

No, and this is the most damaging version of the myth: it still gets handed to families in pediatrician waiting rooms and preschool meetings. Switching to one language doesn't speed up speech development, and it costs the family something real.

When parents stop speaking their native language to a child, the child often loses access to the richest, most emotionally fluent input available. A grandmother who speaks only Tagalog becomes someone the child can no longer talk to. Family stories, humor, and attachment all live in language. Stripping one language away to chase a milestone that wasn't delayed in the first place is a bad trade.

The AAP's 2017 guidance on dual language learners is explicit: families should keep the home language while children also pick up the community language. ^[2] Quality of input matters far more than quantity. A parent who speaks hesitant, uncomfortable English to a toddler gives worse input than a parent who speaks fluent, loving Mandarin.

If a child has a genuine speech or language disorder, the disorder lives in both languages at once. Dropping one language doesn't treat it, it just cuts off one of the child's linguistic systems. ^[1]

Typical bilingual development vs. a real delay

This is the genuinely hard question, and it demands looking at both languages, not one.

A few patterns fit typical bilingual development and aren't red flags on their own: different vocabulary strengths in each language depending on context (home versus school), code-switching within sentences, a "silent period" of quiet reception when a new language is introduced (sometimes lasting weeks), and stronger grammar in one language than the other.

Other patterns are red flags regardless of language background: no babbling or vocal play by 12 months, no single words by 16 months in either language, no two-word combinations by 24 months in either language, loss of words or skills that were already present, trouble understanding simple directions in either language, or limited eye contact, pointing, and joint attention (social communication skills that sit outside any specific language).

The phrase that matters is "in either language." A true language disorder shows up across both, not only in the weaker one. If a child has no words in Spanish and no words in English by 18 months, that's a delay. If they have words in Spanish but not yet in English two months after starting an English-only preschool, that's probably a language shift.

A qualified speech therapy evaluation should always assess both languages. Standardized tests normed on monolingual children shouldn't be the sole measure for bilingual kids. Dynamic assessment, which tests how a child learns rather than what they already know, is more valid for this population. ^[5]

If you're seeing patterns that worry you, early intervention services in the U.S. are available free under IDEA Part C for children under 3, and bilingual assessment is a reasonable request.

Why total vocabulary is what actually matters

Total conceptual vocabulary is the count of concepts a child can express in at least one of their languages, not the count of words in any single language. It's the correct unit for measuring a bilingual child's word learning.

Here's why it matters in practice. Say a 24-month-old bilingual English-Spanish child says "dog" in English but not in Spanish, and says "agua" in Spanish but not in English. A monolingual count in English gives you 1 word. A monolingual count in Spanish also gives you 1 word. But her total conceptual vocabulary is 2 concepts, and that's what should be counted. ^[3]

Pearson and colleagues published research in the early 1990s and 2000s showing that when you measure bilingual toddlers this way, their vocabulary development tracks closely with monolingual norms. Their 1993 paper in the Journal of Speech and Hearing Research documented this across a sample of 25 bilingual children and is still a foundational citation in this field. ^[3]

So if your child's SLP raises a concern about your bilingual child's vocabulary, ask exactly how they're counting. If they're only counting words in English, or only in the second language, that count is incomplete and can mislead.

Does bilingualism make things harder for a child who has autism or another developmental difference?

Families of autistic children, or children with a suspected developmental difference, ask this a lot, and the answer is reassuring: nothing in the research says bilingualism harms autistic children or makes communication harder for them.

Studies comparing bilingual and monolingual autistic children have found no evidence that bilingualism drags language outcomes down. A 2016 systematic review in the Journal of Child Language reached the same conclusion: bilingual and multilingual autistic children did not have worse language outcomes than monolingual autistic children. ^[8]

The same rule holds for families using augmentative and alternative communication (AAC): don't drop either language. AAC devices can be set up to support both, and a child's system should match whatever language or languages surround them at home.

If your child shows patterns like echolalia or other unusual speech development alongside a bilingual upbringing, it's worth pursuing an evaluation for autism spectrum or something like childhood apraxia of speech, and that evaluation should still take both languages into account.

Little Words, an AI speech companion app built for neurodivergent kids, works in multiple languages, so home language practice doesn't have to pause. If you're curious whether it's a fit, the two-minute quiz at the start page will tell you.

What should I ask the pediatrician if I'm worried about my bilingual child's speech?

Go in ready to push back gently if the first answer you get is "wait and see, bilingual kids just take longer." That isn't a current, evidence-based recommendation.

Ask whether your child's communication is being evaluated across both languages. The answer should be yes, or you should hear that a referral to a bilingual SLP is needed. Ask what would actually trigger a referral for a speech-language evaluation, and get a real threshold, not a vague one. If the pediatrician can't name one, or it sits much later than standard milestones, getting a second opinion is reasonable. And ask whether your child qualifies for early intervention services. In the U.S., children under 3 who qualify get free services through IDEA Part C, run through each state's early intervention program, and parents can self-refer, meaning you don't need a doctor's referral to request an evaluation. ^[9] If your child is over 3, the school district handles evaluation and services under IDEA Part B, and you can request this in writing directly from the district. ^[9]

Don't lose years because someone blamed bilingualism for a delay. The window for early language development is real, and early intervention consistently produces better outcomes the sooner it starts.

Can bilingual input actually help brain development?

The evidence here is genuinely interesting, though it's easy to oversell.

There's a well-documented line of research showing that managing two language systems exercises executive function, specifically the ability to selectively attend and suppress competing information. Ellen Bialystok's decades of work at York University on bilingual cognitive advantages is the most cited body of evidence. ^[7] Whether this turns into meaningful real-world advantages in young children is still debated, and some researchers question how reliably specific claims replicate.

Less contested: bilingual children tend to develop metalinguistic awareness (the ability to think about language as a system) somewhat earlier than monolingual peers. They grasp, for instance, that the same object can carry two different names in two different languages, which means understanding early that words are arbitrary symbols. That can lay groundwork for later reading and literacy. ^[4]

None of this means you should treat bilingualism as brain training. The best reason to raise a child bilingually is access: to family, culture, community, opportunity. That's reason enough on its own. The cognitive findings are a bonus, not the point.

Where do clinicians most often get bilingual assessments wrong?

This matters because plenty of parents end up with clinicians who were never specifically trained in bilingual assessment, and a flawed evaluation can cause both under-identification and over-identification of disorders.

One common error is using monolingual norms: most standardized speech and language tests were normed on monolingual English speakers, and applying those norms straight to a bilingual child will nearly always make the child look worse than they are. ^[5] Another is testing only in English. A child who's been in English preschool for six months may show limits in English that simply reflect normal language learning, not a disorder, so the evaluation needs to include the home language too. Clinicians also sometimes count code-switching as an error, but it isn't a grammatical mistake, and transcribing code-switched speech as "incorrect" inflates error counts for no good reason. Another pitfall is mistaking a dominance shift for regression: when a child starts English schooling and English quickly takes over, the home language can look like it's fading, but that's an expected result of intense new-language exposure, not language loss in the clinical sense. Finally, leaning on parent report from only one language context is risky. A parent who only speaks Spanish with the child may not be able to judge the child's English accurately, and the reverse is just as true. Good assessment draws on both home and school.

ASHA's Practice Portal on bilingual service delivery covers appropriate assessment strategies in detail and is worth bringing up with your child's evaluation team. ^[1]

How common are speech and language disorders in bilingual children, really?

About 7 to 8 percent of children have developmental language disorder, and that rate holds steady across monolingual and bilingual populations. ^[5] There's no credible evidence that bilingual children face a higher rate.

Roughly 1 in 12 children ages 3 to 17 in the U.S. has had a voice, speech, language, or swallowing disorder, according to the National Institute on Deafness and Other Communication Disorders (NIDCD). ^[10] That figure isn't broken down by language background in federal data, which is a real gap in population-level surveillance.

What the research does show clearly is that bilingual children are hit harder by diagnostic error. A 2008 study in Language, Speech, and Hearing Services in Schools found that speech-language pathologists, even experienced ones, struggled to separate typical bilingual language patterns from genuine disorder when given case descriptions. ^[11] That's not a character flaw in clinicians; it's a training and tooling gap. For parents, the practical takeaway is simple: if your bilingual child is referred for evaluation, ask about the clinician's specific experience with bilingual assessment. It's a fair, reasonable question to ask.

Frequently asked questions

Do bilingual children start talking later than monolingual children?

No. Bilingual children reach the same major speech and language milestones on the same timeline as monolingual children. First words by 12 months, two-word combinations by 24 months, and sentences by 36 months are the benchmarks for both groups. The myth that bilingual children are naturally later talkers is not supported by research and should not delay evaluation when there are real concerns.

Is it okay to raise a child bilingual if they already have a speech delay?

Yes. A speech or language disorder exists in both languages at once. Dropping one language does not treat the disorder; it only removes one of the child's linguistic resources. ASHA and the AAP both recommend that families keep the home language even when a child has a diagnosed delay or disorder. The speech therapy should address both languages, not ask the family to abandon one.

What is code-switching and is it a problem?

Code-switching is when a bilingual speaker mixes two languages within the same conversation or sentence. It is normal, sophisticated linguistic behavior, not confusion or a sign of disorder. Bilingual children as young as 2 code-switch in grammatically consistent ways. A clinician who counts code-switching as an error in a language sample is making an assessment mistake.

How should vocabulary be measured in a bilingual child?

Through total conceptual vocabulary: counting the concepts a child can express in at least one language, not words in a single language alone. If a child says "cat" in English and "perro" in Spanish, that counts as two concepts. Research by Pearson and colleagues showed that bilingual toddlers' total conceptual vocabulary tracks closely with monolingual norms, even though single-language counts look lower.

At what age should I be concerned about my bilingual child's speech?

Use the same milestones as for monolingual children, applied across both languages. No words in either language by 16 months, no two-word combinations in either language by 24 months, or loss of skills already acquired are all reasons to request an evaluation promptly. Being bilingual does not push these thresholds later. You can self-refer for early intervention services in the U.S. without a doctor's referral.

Can a child with autism be raised bilingually?

Yes. Research does not support the idea that bilingualism worsens outcomes for autistic children. Studies comparing bilingual and monolingual autistic children have found no significant difference in language outcomes. Families of autistic children should not be advised to drop the home language. AAC systems can also be configured to support multiple languages.

What is a bilingual speech-language evaluation and where do I find one?

A bilingual evaluation assesses a child's communication skills in both languages, uses assessment tools appropriate for bilingual populations rather than monolingual norms, and considers language history, input, and context. ASHA's ProFind directory at asha.org lets you filter for bilingual providers. Telehealth has widened the pool of bilingual SLPs available to families without local access.

Will my child get confused if we speak two languages at home?

No. Language confusion is not a real clinical phenomenon in bilingual development. Children exposed to two languages from infancy build separate representations for each. What looks like confusion to observers, such as code-switching or a pause before answering, is normal bilingual processing. The human brain handles multiple languages well; that is not in question scientifically.

Does it matter which language I speak to my child if I want to support their development?

Speak the language you speak most fluently, warmly, and naturally. Quality of input matters more than which language it's in. A parent who speaks halting, uncomfortable English gives worse linguistic modeling than a parent who speaks rich, expressive Cantonese. If the community or school language differs from your home language, your child will pick it up through exposure there. Your job at home is to give the best input you can, and that means your strongest language.

Are there tests designed specifically for bilingual children?

Yes, though the options vary by language pair. The Bilingual English-Spanish Assessment (BESA) and the Spanish-English Language Assessment (SELA) are among the tools designed for Spanish-English bilingual children. Dynamic assessment, which measures how a child learns new language rather than what they already know, is considered particularly valid for bilingual populations and is recommended by ASHA.

What happens if my bilingual child only gets assessed in English?

You risk an incomplete and potentially misleading picture. A child who is stronger in their home language than in English will appear to have larger deficits than they actually have. This can lead to over-identification of a disorder that isn't there, or a skewed sense of severity. Any evaluation that covers only one language should be treated as preliminary, not definitive.

What early intervention services are available for bilingual children in the U.S.?

Under IDEA Part C, children under 3 with developmental delays are entitled to free early intervention services, including speech-language therapy. Parents can self-refer directly to their state's early intervention program without a physician's referral. Services should be provided in the child's natural environment and, where possible, in the family's home language. After age 3, services shift to Part B, run through school districts.

Does growing up bilingual protect against speech disorders?

No. The rate of developmental language disorder is about 7 percent in both bilingual and monolingual children. Bilingualism is neutral on disorder risk, neither protective nor harmful. Some research suggests cognitive advantages from managing two languages, particularly in executive function, but these do not prevent speech or language disorders from occurring.

My child stopped speaking their home language after starting English-only school. Is this a disorder?

Probably not, though it warrants watching. When children enter intensive single-language schooling, the school language often becomes dominant fast and the home language weakens, temporarily or significantly. This is called subtractive bilingualism and is a social and environmental outcome, not a language disorder. Keeping rich home-language input at home is the best way to sustain both languages.

Sources

1. ASHA, Bilingual Service Delivery Practice Portal: Being bilingual or multilingual does not cause speech, language, or communication disorders; assessment must cover both languages.
2. American Academy of Pediatrics, Promoting Optimal Development: Identifying Infants and Young Children With Developmental Disorders (2017): AAP affirms that dual language learners reach communicative milestones at the same rate as monolingual peers and that families should be encouraged to maintain the home language.
3. Pearson, Fernandez & Oller (1993), Journal of Speech and Hearing Research: Lexical development in bilingual infants and toddlers: Bilingual toddlers' total conceptual vocabulary tracks closely with monolingual norms when measured across both languages; single-language counts underestimate bilingual lexical knowledge.
4. Genesee, Paradis & Crago (2004), Dual Language Development and Disorders, Brookes Publishing: Code-switching in bilingual children is grammatically rule-governed and is not evidence of confusion or disorder; bilingual children develop metalinguistic awareness earlier on average.
5. Kohnert (2010), Journal of Speech, Language, and Hearing Research: Bilingual children with primary language impairment: The prevalence of developmental language disorder is approximately 7 percent in bilingual children, the same as in monolingual children; clinician errors in distinguishing typical bilingual patterns from disorder are documented.
6. Paradis, Genesee & Crago (2011), Dual Language Development and Disorders 2nd ed., review of bilingual language impairment prevalence: Review of available studies finds no credible evidence that bilingualism increases the risk of language impairment.
7. Bialystok (2009), Developmental Science: Bilingualism: The good, the bad, and the indifferent: Managing two language systems exercises executive function; high bilingual proficiency may confer cognitive advantages including stronger selective attention.
8. Uljarević et al. (2016), Journal of Child Language: A systematic review of bilingualism and autism: Bilingual and multilingual autistic children do not have worse language outcomes than monolingual autistic children; bilingualism does not negatively affect autism symptom severity.
9. U.S. Department of Education, IDEA Part C and Part B overview: Under IDEA Part C, children under 3 with developmental delays are entitled to free early intervention services; parents can self-refer without a physician's referral.
10. NIDCD, Statistics on Voice, Speech, and Language: Approximately 1 in 12 children ages 3 to 17 in the U.S. has had a voice, speech, language, or swallowing disorder.
11. Bedore & Peña (2008), Language, Speech, and Hearing Services in Schools: Assessment of bilingual children for identification of language impairment: Standardized tests normed on monolingual children should not be used as the sole assessment measure for bilingual children; dynamic assessment is more valid for this population; clinicians struggle to separate typical bilingual patterns from disorder.
12. ASHA, Find a Member / Certified Provider Directory: ASHA maintains a searchable directory of certified speech-language pathologists that can be filtered by language background and specialty.