The clearest signs your baby understands sign language are not the signs they make back to you, but the way they respond before they can produce any signs at all. If your eight-month-old lights up with excitement when you sign “milk” before a feeding, or turns to look at the family dog when you sign “dog,” your baby is already comprehending sign language — even if their hands have not yet figured out how to form a single gesture in return. This gap between understanding and doing is completely normal. Just as babies understand the word “no” long before they can say it, receptive sign language comprehension reliably precedes production by weeks or even months.
Most babies begin signing back to caregivers between ten and fourteen months of age, though some children of deaf parents who use ASL exclusively produce their first signs as early as eight to nine months. The journey from a blank stare to an enthusiastic, if clumsy, attempt at signing “more” at the dinner table typically takes about two months of consistent practice. During that waiting period, you will see subtler signals — anticipatory excitement, correct behavioral responses, and early attempts at imitating your hand movements — that confirm your baby is absorbing what you are teaching. This article walks through each of those indicators in detail, explains the developmental timeline behind them, covers what the research actually says about long-term benefits, and offers practical guidance for parents who are wondering whether any of this is working.
Table of Contents
- What Are the First Signs a Baby Understands Sign Language?
- When Should Babies Start Showing Comprehension of Signs?
- How Receptive Understanding Develops Before a Baby Signs Back
- Practical Ways to Test Whether Your Baby Recognizes Signs
- Why Some Babies Take Longer to Sign Back and When to Be Concerned
- What the Research Says About Long-Term Benefits of Baby Sign Language
- Emerging Research and the Broader Picture
- Conclusion
- Frequently Asked Questions
What Are the First Signs a Baby Understands Sign Language?
The earliest indicator is what researchers and pediatric experts call anticipatory excitement. When you consistently sign “milk” before breastfeeding or bottle time, your baby will eventually begin to react to the sign itself — bouncing, kicking their legs, or opening their mouth — before the milk arrives. This is not a coincidence or a response to other contextual cues like sitting in the high chair. You can test it by signing in an unexpected setting. If your baby still perks up, they are responding to the sign. According to Huckleberry, this visible excitement when seeing a familiar sign is one of the most reliable early markers of comprehension. The second key indicator is appropriate behavioral response. Your baby looks at the right object when you sign its name.
They calm down when you sign “milk” during a fussy moment. They stop eating and lift their arms when you sign “all done.” These responses show that your child has mapped the gesture to its meaning, which is the foundation of all language. Pampers notes that these correct behavioral reactions — looking, calming, stopping, reaching — are strong evidence of sign comprehension even in the absence of any signing back. A third sign is gesture imitation, however imperfect. Your baby may see you sign “eat” and bring their fist vaguely toward their mouth, or watch you sign “more” and clap their hands together in a rough approximation. Infants quickly note connections between items and symbolic gestures and will attempt to copy them, even when their motor control is not yet refined enough to produce the sign accurately. These clumsy early attempts are not errors. They are proof that your baby is actively processing and trying to participate in the conversation.
When Should Babies Start Showing Comprehension of Signs?
The developmental window for baby sign language comprehension is more predictable than many parents realize. Experts at the Cleveland Clinic and Pathways.org recommend introducing signs between six and nine months of age, when babies develop the physical dexterity and cognitive ability needed for this kind of learning. At this stage, babies can maintain eye contact and show clear interest in communicating, both prerequisites for sign language uptake. By eight to nine months, most hearing babies begin making signs in response to caregivers, though this varies. However, if you started signing at six months and see nothing at eight months, that does not mean it is not working. The Bump and Today’s Parent both note that most babies begin signing back between ten and fourteen months, and those early signs will often be imprecise approximations rather than textbook ASL.
According to reporting from Today.com, parents should expect roughly two months of consistent practice before a baby may begin signing back. The lag between when you start teaching and when your baby responds can feel discouraging, but it mirrors what happens with spoken language. Babies understand dozens of spoken words before they utter their first one. One practical detail worth noting: many babies can make “C” and “O” shapes with their hands around nine to ten months, according to Tinyhood. Signs that use these hand shapes — like “more,” “milk,” or “cookie” — tend to be among the first that babies successfully produce. If you are choosing which signs to introduce first, picking ones that match your baby’s current motor abilities will shorten the gap between comprehension and production.
How Receptive Understanding Develops Before a Baby Signs Back
The concept that receptive understanding precedes production is one of the most important things for parents to internalize. It is the reason so many families give up on baby sign language prematurely. They teach signs for weeks, see no signing back, and conclude it is not working. But as The Bump explains, babies understand signs well before they can produce them, in exactly the same way that spoken language comprehension precedes speech. Your baby may understand fifteen signs and produce zero. That is not failure. That is normal development. Consider a specific example. A parent signs “bath” every evening before bath time starting at seven months.
At nine months, the baby still has not signed “bath” back. But the parent notices that when they sign “bath” in the living room — nowhere near the bathroom — the baby crawls toward the hallway that leads to the bathroom. That is receptive comprehension. The baby has linked the sign to the concept and is acting on it, even though their hands cannot yet form the gesture. This kind of observation requires parents to look beyond the hands and watch the whole child: their eyes, their body language, their movements, their emotional responses. The 1988 research by Acredolo and Goodwyn found that eighty-seven percent of infants surveyed had at least one sign in their gestural vocabulary, which suggests that nearly all babies are already using symbolic gestures naturally. The formal teaching of baby sign language builds on an instinct that is already there. Your baby is predisposed to communicate with their hands. The question is not whether they will understand, but whether you will recognize the understanding when it appears.
Practical Ways to Test Whether Your Baby Recognizes Signs
If you want to move beyond guesswork and actually confirm that your baby is picking up signs, there are a few straightforward approaches. The simplest is the out-of-context test. If you always sign “eat” in the kitchen, try signing it in the car or at the park. If your baby responds — by looking at you expectantly, smacking their lips, or getting excited — the sign itself is what they are responding to, not the environmental cues. This distinction matters because babies are excellent at reading routines and contexts, and you want to confirm they are reading the sign, not just the situation. Another approach is to offer choices using signs. Sign “milk” and “water” and see which one your baby reaches for.
If they consistently reach for the correct item, they are demonstrating comprehension of both signs. This method has a built-in tradeoff: it works best with signs your baby encounters frequently, and it can produce unreliable results with signs you have only recently introduced. A baby who has seen “milk” signed five hundred times and “water” signed twenty times may always reach for the familiar one regardless of their actual preference. You can also watch for what does not happen. If you sign “all done” and your baby keeps eating happily, they may not yet associate that sign with the end of a meal. But if you sign “all done” and they pause, look at you, or start fussing because they are not actually done, that reaction — even a negative one — confirms comprehension. The absence of a response is ambiguous. A contextually appropriate response, whether positive or resistant, is informative.
Why Some Babies Take Longer to Sign Back and When to Be Concerned
Individual variation in baby sign language production is enormous, and parents should resist the urge to compare their child’s timeline to anyone else’s. Some babies sign back at eight months. Others do not produce recognizable signs until well past their first birthday. Factors that influence timing include motor development, temperament, how consistently signs are modeled, and whether multiple caregivers are using the same signs. A baby who sees signs from one parent for twenty minutes a day will generally progress more slowly than a baby whose daycare provider, grandparents, and both parents all sign consistently. There is an important limitation to acknowledge here. While baby sign language can be a helpful communication bridge, it is not a diagnostic tool for language delays.
A baby who is slow to sign back is not necessarily experiencing a developmental problem. However, if your baby shows no response to signs or spoken words by twelve months — no anticipatory excitement, no looking at named objects, no behavioral responses to any form of communication — it is worth discussing with your pediatrician. The issue in that case is not about signing specifically but about receptive language development more broadly. A 2022 systematic review published in the Journal of Speech, Language, and Hearing Research confirmed that learning sign language does not hinder spoken language acquisition. This finding should reassure parents who worry that teaching signs might delay their baby’s motivation to talk. It does not. The research is clear on this point. What signing does reliably produce, according to findings from Bright Horizons and Michigan State University Extension, are emotional and practical benefits: reduced frustration, fewer tantrums, stronger parent-child bonding, and caregivers who become more responsive to their baby’s nonverbal cues.
What the Research Says About Long-Term Benefits of Baby Sign Language
The most frequently cited study on baby sign language outcomes is the NIH-funded research by Acredolo, Goodwyn, and Brown, published in 2000. That study compared thirty-two sign-trained children with thirty-two verbal-trained children and thirty-nine controls. From eleven months through twenty-four months, the sign-trained group showed statistically higher receptive and expressive language outcomes, with verbal skills approximately three months ahead of non-signers by age two. A follow-up by the same researchers reported that signing children averaged an IQ of 114 at age eight, compared to 102 for non-signing peers.
However, that IQ finding has not been published in a peer-reviewed journal, which means it should be treated with caution rather than cited as settled science. Marilyn Daniels at Penn State conducted a ten-year study showing that preschoolers and kindergarteners taught ASL consistently scored fifteen to twenty percent higher on vocabulary measures and reading levels than non-signing peers on the Peabody Vocabulary Test. Research by Rowe and Goldin-Meadow in 2009 found that the number of gestures a child used between fourteen and eighteen months correlated with vocabulary size at kindergarten entry, with differences also linked to socioeconomic status. And Kirk and colleagues in 2012 found that children classified as low-ability linguistically showed the largest gains from sign training, suggesting particular benefits for children with weaker language skills. That said, subsequent controlled studies by Johnston in 2005, Kirk in 2013, and Fitzpatrick in 2014 found no statistically significant long-term vocabulary advantage for baby signers, which means the most honest summary of the evidence is that signing clearly helps in the short term but its long-term academic impact remains debated.
Emerging Research and the Broader Picture
A February 2025 article from Indiana University confirmed that baby sign language increases early literacy skills, including letter recognition and phonemic awareness. This line of research suggests that the benefits of signing may extend beyond vocabulary into foundational reading skills, which would represent a meaningful addition to the evidence base if replicated in larger studies.
The most consistent and least contested finding across all the research is that baby sign language reduces frustration for both parent and child during the gap between when a baby can understand language and when they can speak it. Whether or not signing produces measurable IQ gains or long-term vocabulary advantages, it gives families a working communication system months before speech arrives. For most parents, that practical benefit — fewer meltdowns, more connection, a baby who can tell you they want more banana before dissolving into tears — is reason enough.
Conclusion
The signs that your baby understands sign language are visible well before your baby signs back to you. Anticipatory excitement, appropriate behavioral responses, looking at the correct objects, and clumsy attempts at imitating your hand movements all indicate that comprehension is developing. Most babies begin producing signs between ten and fourteen months after roughly two months of consistent exposure, but the receptive understanding that precedes production is just as meaningful and just as real.
If you are in the early weeks of teaching signs and wondering whether your baby is getting anything out of it, shift your attention from their hands to their whole body. Watch their eyes, their posture, their emotional reactions when you sign. The research supports what attentive parents have always noticed: babies are understanding far more than they can express. Signing simply gives you a window into that understanding and gives your baby a way to participate in the conversation sooner.
Frequently Asked Questions
At what age should I start teaching my baby sign language?
Experts recommend introducing signs between six and nine months, when babies can maintain eye contact and show interest in communicating. You can start earlier, but most babies will not have the cognitive and physical readiness to respond until this window.
How long does it take for a baby to sign back?
Expect about two months of consistent practice before your baby may begin signing back. Most babies start producing signs between ten and fourteen months, though some begin as early as eight to nine months.
Will teaching sign language delay my baby’s speech?
No. A 2022 systematic review in the Journal of Speech, Language, and Hearing Research confirmed that learning sign language does not hinder spoken language acquisition. Research consistently shows either neutral or positive effects on verbal development.
What are the easiest first signs to teach?
Signs that use “C” and “O” hand shapes tend to be easiest for babies around nine to ten months, since many babies can form these shapes at that age. Common starter signs include “more,” “milk,” “eat,” and “all done” because they connect to frequent daily activities.
Does baby sign language actually boost IQ?
One follow-up study found signing children averaged an IQ of 114 versus 102 for non-signers at age eight, but that finding was never published in a peer-reviewed journal. The most reliably supported benefits are reduced frustration, fewer tantrums, and stronger parent-child bonding rather than long-term cognitive gains.
My baby is fourteen months old and still not signing back. Should I be worried?
Not necessarily. Individual timelines vary widely based on motor development, temperament, and consistency of exposure. However, if your baby shows no response to any form of communication — signs or spoken words — by twelve months, consult your pediatrician to rule out broader developmental concerns.