Teaching sign language to hearing children does not delay speech. The largest controlled study on this question, involving over 1,300 typically developing children, found that exposure to baby sign had no negative effect on spoken vocabulary development.1First Language. The impact of baby sign on vocabulary development That finding aligns with what developmental researchers have observed for decades: gesture and speech are deeply intertwined in the brain, and adding one does not subtract from the other. But the real story is more nuanced than a simple “no,” because the popular claims about baby sign go well beyond what the science supports in both directions.
What the Largest Studies Actually Found
The worry that signing might replace or crowd out spoken words sounds intuitive. If a baby can get what they want by waving their hands, why bother learning to talk? In practice, that is not what happens. The large French study mentioned above compared 723 children exposed to baby sign at home with 625 non-exposed peers, all typically developing and hearing. After adjusting for family income and how much parents read and played with their children, the researchers found weak to no effect of baby sign on vocabulary size in either direction. Signing did not hurt, but it did not produce the dramatic vocabulary boost that many baby-sign programs promise either.1First Language. The impact of baby sign on vocabulary development
A separate line of evidence comes from children who are genuinely bilingual in a spoken language and a sign language. A study of deaf and hard-of-hearing children learning both American Sign Language and spoken English found that ASL vocabulary size was positively correlated with spoken English vocabulary size. Children with large ASL vocabularies were actually more likely to have spoken English vocabularies in the typical range for hearing children their age.2PubMed Central. Learning a Sign Language Does Not Hinder Acquisition of a Spoken Language This is a stronger test than baby sign with hearing infants, because these children were using a full sign language daily, not just a handful of symbolic gestures. Even at that level of signing, spoken language was not crowded out.
Why Gesture and Speech Use the Same Brain Wiring
The reason signing does not compete with speech is rooted in how the brain processes communication. Gesture and spoken language are not handled by separate neural systems that fight for bandwidth. Neuroimaging research shows substantial overlap in the brain regions activated when people observe or produce gestures versus when they process speech. The left inferior frontal region, which includes the area long associated with language production, lights up strongly for both communicative gestures and speech.3PubMed Central. Brain function overlaps when people observe emblems, speech, and grasping
Further research has identified a functional network connected to that same frontal language area that is shared across speech, gesture, and gesture produced alongside speech. The network includes brain regions involved in motor control, suggesting that the coordination of speech and gesture relies on common motor planning circuits.4PubMed. A common functional neural network for overt production of speech and gesture In plain terms, your brain does not treat hand movements and mouth movements as unrelated activities. They are woven together at a fundamental level, which is why people gesture spontaneously while talking and why watching someone gesture while they speak improves comprehension.
Studies using eye-tracking have also shown that brain areas involved in preparing and producing physical actions play an active role in understanding co-speech gestures during language comprehension.5Current Biology. Gestures Orchestrate Brain Networks for Language Understanding The upshot is that practicing gesture-based communication exercises many of the same circuits that spoken language depends on. Training one tends to support the other, not undermine it.
Gesture as a Stepping Stone to Words
Long before anyone marketed baby sign classes, developmental researchers noticed something striking about how children naturally acquire language. Babies gesture before they speak. They point, wave, and reach in communicative ways months before they say their first words. And those early gestures are not random. Research tracking individual children found that many of the specific concepts a child first expressed through gesture later appeared in that child’s spoken vocabulary. Children who were first to combine a gesture with a word to express a two-part idea (like pointing at a bird while saying “nap”) were also the first to produce two-word spoken combinations like “bird nap.”6PubMed. Gesture paves the way for language development
This means gesture is not a detour away from speech. It is part of the normal on-ramp. Changes in what a child does with their hands reliably predict what they will be doing with their mouth a few months later. Teaching a child signs is, from the brain’s perspective, an extension of what the child is already doing naturally. You are adding to their gestural toolkit, not diverting them from a spoken-language track.
The Overpromise Problem
If the “baby sign delays speech” worry is unfounded, so is the opposite claim that is equally common: that baby sign will make your child smarter, give them a bigger vocabulary, or advance their IQ. A systematic look at the evidence cited by commercial baby sign websites found that over 90 percent of the “supporting research” they referenced consisted of opinion articles without data or product descriptions. Only eight of the 82 cited pieces were actual empirical studies relevant to the question of whether teaching signs to hearing infants improves developmental outcomes.7Infant and Child Development. Evidence for Website Claims about the Benefits of Teaching Sign Language to Infants and Toddlers with Normal Hearing
The researchers concluded that there was simply not enough high-quality evidence to draw research-based conclusions about whether baby sign produces better developmental outcomes in typically developing children. That assessment has largely held up. The large French study confirmed the pattern: signing did not hurt, but it did not deliver a measurable vocabulary advantage either.8First Language. The impact of baby sign on vocabulary development If you enjoy signing with your baby and it feels like a meaningful way to connect, the evidence says that is perfectly fine. But if you are paying for an expensive curriculum because you were promised it would make your child a better reader by age six, the science does not back that up.
Sign Language for Children with Developmental Differences
The picture shifts when you move from typically developing children to children with speech or developmental challenges. Here, the evidence for sign as a communication tool is stronger, and in some cases clinicians actively recommend it.
For children on the autism spectrum, several studies have explored whether sign language training helps or hinders spoken language. Early research found that simultaneous speech and sign training could support the development of speech skills in autistic children.9PubMed. Sign language and autism A comparison of sign language training with another common approach found that sign language training actually produced a higher percentage of vocalizations during sessions.10Focus on Autism and Other Developmental Disabilities. Comparing the Picture Exchange Communication System and Sign Language Training for Children With Autism That is a meaningful finding: far from suppressing speech, the act of learning signs seemed to draw more spoken attempts out of the children.
The relationship between signing and speaking in this population is not one-size-fits-all, though. One study found that conditions involving spoken presentation (either speech alone or simultaneous speech and sign) produced more child-initiated speech during treatment than a sign-alone condition.11PubMed. Speech following sign language training in autistic children with minimal verbal language The takeaway is that pairing sign with speech appears to be the sweet spot for encouraging vocalization, while using sign without any spoken model may not push speech production as effectively. Most clinical practice today uses sign as a bridge alongside spoken language, not as a replacement for it.
A compelling case study in this vein involved a three-year-old boy suspected of having childhood apraxia of speech, a condition where the brain has difficulty coordinating the movements needed for clear speech. His family introduced sign language early, and when combined with intensive speech therapy, his symptoms resolved rapidly. His clinicians concluded that sign language served as an effective form of language development that supported, rather than competed with, his spoken communication progress.12Pediatrics. Bridging the Gap Between Speech and Language: Using Multimodal Treatment in a Child With Apraxia
The Cochlear Implant Debate
If there is one area where the “sign language and speech” question gets genuinely complicated and contested, it is in children who are deaf or hard of hearing and receive cochlear implants. This is the one context where some research has flagged a potential tradeoff, though the interpretation is fiercely debated.
A review of outcomes after cochlear implantation noted that learning sign language before surgery may improve subsequent language outcomes and support cognitive and social-emotional development.13PubMed Central. Language outcomes after cochlear implant However, a study tracking children over several years after implantation found a different pattern for spoken language specifically: children without early sign language exposure achieved better speech recognition in the first three years post-implant and showed an advantage in spoken language and reading near the end of elementary school. Over 70 percent of children without sign exposure achieved age-appropriate spoken language, compared with about 39 percent of those exposed to sign for three or more years. Speech intelligibility scores were also higher in the non-signing group.14PubMed Central. Early Sign Language Exposure and Cochlear Implantation Benefits
These numbers look alarming at first glance, but context matters. Children who receive sign language exposure before implantation often come from families where deafness was identified earlier, or where spoken-language access was more limited before the implant. In other words, the children who were exposed to sign may have had less auditory input overall, not because sign caused a problem but because their hearing loss was more severe or less well-managed prior to implantation. The study design makes it hard to separate the effect of sign exposure from the effect of delayed auditory access.
This debate is specific to cochlear implant rehabilitation, where the clinical goal is typically to maximize spoken language use through intensive auditory training. It does not apply to hearing children or to deaf children not on a cochlear implant track. And even within the implant community, many researchers and families argue that the cognitive and social benefits of early sign access outweigh any short-term tradeoff in spoken-language milestones, because a child with no functional language system at all during a critical developmental window faces far greater risks than a child who signs while waiting for or adjusting to an implant.
How Sign Changes the Parent-Child Dynamic
One benefit of baby sign that does show up consistently in research has less to do with the child’s vocabulary and more to do with how parents interact with their children. A study of families in lower-income communities who participated in an infant sign intervention found that mothers in the signing group became more attuned to changes in their children’s emotional states and more responsive to distress cues.15Early Childhood Research Quarterly. Infant signs as intervention? Promoting symbolic gestures for preverbal children in low-income families supports responsive parent–child relationships
This makes intuitive sense. When you are actively watching your baby’s hands for communicative signals, you are paying closer attention to your baby overall. You are looking for intention, reading expressions, responding to attempts at communication. That kind of attentive, responsive parenting is one of the most robust predictors of good language outcomes, regardless of whether signing is involved. So while baby sign itself may not turbocharge vocabulary, the habit of close, responsive interaction that signing encourages may quietly support development through a different channel.
Cultural Variation in How Families Use Signs
The baby sign movement has been primarily marketed to English-speaking Western families, but how parents and children use early gestures varies across cultures in interesting ways. A cross-cultural comparison of infant sign use in the United States and Taiwan found that cultural differences in parents’ and children’s signing patterns mirrored known differences in early spoken words. American families tended to emphasize object labels (naming things), while Taiwanese families leaned more toward regulatory communication (directing behavior). The researchers interpreted this as evidence that the intergenerational transmission of cultural values through symbols begins before oral language even arrives.16PubMed Central. Cultural transmission through infant signs: Objects and actions in U.S. and Taiwan
This finding is a useful reminder that baby sign is not one uniform thing. What parents sign about, how often they sign, and why they sign all reflect broader cultural patterns in how adults communicate with children. A parent who uses signs primarily to label objects (“dog,” “milk,” “ball”) is engaging a different slice of language development than a parent who uses signs primarily to manage behavior (“stop,” “gentle,” “wait”). The content and style of signing may matter at least as much as whether signing happens at all.
What Hearing Bimodal Bilinguals Tell Us
An interesting window into how sign and speech coexist comes from hearing adults who are fluent in both a spoken language and a sign language. Research on these “bimodal bilinguals” has found that the two languages do influence each other, but not in ways that suggest one suppresses the other. A study of Dutch speakers who were also fluent in Dutch Sign Language found that their sign language habits subtly influenced how they structured certain spatial descriptions in speech, leading them to mention background objects before foreground objects more often than non-signing Dutch speakers did. The reverse influence, from speech habits into their signing, did not appear.17Bilingualism: Language and Cognition. Word order preference in sign influences speech in hearing bimodal bilinguals but not vice versa: Evidence from behavior and eye-gaze
This cross-linguistic influence is similar to what happens between any two languages in a bilingual speaker. Knowing French influences how you structure English sentences, and vice versa. The fact that one language is gestural and the other is spoken does not make the influence damaging; it simply makes it cross-modal. If anything, this research shows how deeply integrated the two systems become, reinforcing the neuroimaging evidence that speech and gesture share fundamental circuitry. For parents wondering whether their child will “get confused” by signing, the adult bilingual data suggest that the brain is perfectly equipped to manage both modalities without one degrading the other.
When to Actually Worry About Speech Development
If your child is signing happily but not producing many words, it is reasonable to ask whether the signing is covering up a problem rather than causing one. The answer depends on the child’s age and the broader picture. Most children say their first words between 12 and 18 months, but the range is wide. A child who is communicating actively through signs, understanding spoken language, and following directions is showing strong language comprehension even if their spoken output is lagging. That comprehension is far more predictive of long-term outcomes than how many words a toddler says at any given month.
Red flags that warrant a conversation with a pediatrician or speech-language pathologist have nothing to do with signing. They include a child who does not respond to their name, does not seem to understand simple spoken requests by 18 months, shows no interest in communicating through any means (speech, gesture, pointing, or sign), or loses skills they previously had. A child who signs enthusiastically and babbles but has not yet hit a spoken-word milestone is in a very different category from a child who shows no communicative intent at all. If you are worried, get an evaluation, but do not assume that removing signs will unlock speech. The evidence consistently points in the opposite direction: giving children more tools for communication supports the whole system, not just the gestural part of it.