Last updated 2026-07-09
TL;DR
Being raised bilingual does not cause speech delay. Research consistently shows bilingual children hit the same major language milestones as monolingual children, on the same timeline. They may mix languages and have smaller vocabularies in each language individually, but their total vocabulary across both languages is comparable. Concerns about delay deserve evaluation regardless of language background.
Growing up bilingual does not cause speech delay, and a child in a two-language home carries no higher risk for a true language disorder. This is one of the most stubborn myths in early childhood development, and it's pushed generations of parents to drop a language, switch to English only, or "wait and see" because bilingual kids supposedly 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 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? Largely from a misreading of vocabulary data. When researchers measured a bilingual child's vocabulary in only one language, 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 also being raised bilingual, the bilingualism is almost certainly not the cause. Something else is worth a closer look.
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, and the right measure is total vocabulary across both languages. Dominant language can also 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. 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 itself, which delays a child's path 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, one that 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, attachment: all of that lives in language. Stripping one 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, that 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 answering it means 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 listening 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 just 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 patterns are worrying you, early intervention services in the U.S. are available free under IDEA Part C for children under 3, and asking for a bilingual assessment is entirely reasonable.
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 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?
Plenty of families of autistic children, or children with a suspected developmental difference, worry about this, and the honest 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: 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 fits your family, the two-minute quiz 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 press for a real threshold rather than a vague one. If the pediatrician can't name one, or it sits much later than standard milestones, a second opinion is reasonable.
Also 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.
No, bilingual kids don't lag behind. They hit the same milestones on the same schedule as monolingual children: first words by 12 months, two-word combinations by 24 months, sentences by 36 months. The idea that bilingual children are naturally later talkers just isn't backed by research, and it shouldn't be a reason to put off an evaluation if something actually seems off. If your child already has a diagnosed speech delay, you can still raise them bilingual, and you should. A language disorder shows up in both languages at once, so dropping one doesn't fix anything. It just takes away one of the child's tools for communicating. Both ASHA and the AAP recommend keeping the home language even when a child has a diagnosis. Therapy should work on both languages rather than ask a family to give one up. You'll also hear about code-switching, when a bilingual speaker blends two languages in the same sentence or conversation. That's normal and actually pretty sophisticated: kids as young as 2 do it in ways that follow consistent grammar rules. If a clinician marks code-switching as an error on a language sample, that's a flaw in the assessment, not in the child. Vocabulary size needs a different kind of counting for bilingual children. The right measure is total conceptual vocabulary, meaning every concept a child can express in either language. A child who says "cat" in English and "perro" in Spanish knows two concepts, not one word said twice. Pearson and colleagues found that when you count this way, bilingual toddlers track closely with monolingual norms, even though a single-language word count would make them look behind. The warning signs to watch for are the same ones you'd watch for in any child, just applied across both languages: no words at all by 16 months, no two-word combinations by 24 months, or losing skills the child already had. Being bilingual doesn't push these timelines back, so don't wait longer than you would otherwise. In the U.S. you can self-refer for early intervention without waiting on a doctor's referral. Autism doesn't change this picture either. Studies comparing bilingual and monolingual autistic children haven't found meaningful differences in language outcomes, so there's no research reason to tell a family to drop the home language. AAC systems can be set up to support more than one language too. If you're looking for a proper evaluation, look for a bilingual assessment: one that tests communication in both languages, uses tools built for bilingual kids rather than monolingual norms, and takes into account the child's language history and home input. ASHA's ProFind directory (asha.org) lets you search for bilingual providers, and telehealth has made it much easier to find one even without local options. Tools like the Bilingual English-Spanish Assessment (BESA) and the Spanish-English Language Assessment (SELA) exist for that language pair specifically, and dynamic assessment, which looks at how a child learns new language rather than what they already know, is considered especially useful for bilingual kids and is recommended by ASHA. If your child only gets assessed in English, treat the results as incomplete: a child who's actually stronger in the home language can look like they have bigger deficits than they really do, which can lead to a disorder being diagnosed when it isn't there. No, speaking two languages at home won't confuse your child. Language confusion between two home languages isn't a real clinical thing. Kids exposed to two languages from infancy build separate mental systems for each one. Code-switching or a pause before answering might look like confusion from the outside, but it's just normal bilingual processing. The brain is well equipped for more than one language, and that's settled science at this point. As for which language to use with your child, speak whichever one you're most fluent and comfortable in. The quality of what you say matters more than which language it's in. Rich, natural Cantonese from a parent who speaks it well will teach a child more than halting, uncomfortable English. If your child needs the school or community language, they'll pick it up through exposure there. Your job at home is to give your best input, and that's your strongest language. Growing up bilingual doesn't protect against speech disorders either. Developmental language disorder shows up at about the same rate, roughly 7 percent, in bilingual and monolingual children alike. Bilingualism is neutral here, not a shield and not a risk. There's some evidence of cognitive benefits from managing two languages, particularly around executive function, but that doesn't stop a language disorder from developing if one is going to. If your child stops using the home language after starting an English-only school, that's usually not a disorder, though it's worth keeping an eye on. Kids in intensive single-language schooling often shift fast toward the school language, and the home language can weaken, sometimes temporarily, sometimes more lastingly. This is called subtractive bilingualism, and it's a social and environmental shift, not a language disorder. Keeping up rich input in the home language is the best way to hold onto both. In the U.S., under IDEA Part C, children under 3 with developmental delays qualify for free early intervention services, including speech-language therapy, and parents can self-refer straight to their state's program without going through a doctor first. Services should happen in the child's natural environment and, when possible, in the family's home language. Once a child turns 3, this shifts to Part B, handled through school districts. This article is for general information and isn't a substitute for an evaluation from a qualified speech-language pathologist.Sources
- ASHA, Bilingual Service Delivery Practice Portal: Being bilingual or multilingual does not cause speech, language, or communication disorders; assessment must cover both languages.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.