Baby sign language follows a predictable developmental arc from about 4 months through 24 months, with most babies ready to receive signs around 4 to 6 months, beginning to sign back between 8 and 12 months, and building a vocabulary of 50 or more signs by their second birthday. The exact timeline varies by child, but understanding what to expect each month helps parents set realistic goals and recognize the small wins that precede those first intentional signs. For instance, a 9-month-old who watches your hands intently when you sign “milk” is showing receptive understanding weeks before they will produce the sign themselves.
This article breaks down what happens during each phase of the baby sign language journey, from those early months when you are simply modeling signs with little visible response, through the exciting period when signs start clicking, and into the toddler months when signing becomes a genuine communication tool. You will learn which signs work best at different ages, how to adjust your teaching approach as your baby grows, and what realistic expectations look like along the way. We will also cover common roadblocks and how to work through them when progress stalls.
Table of Contents
- What Happens in Baby Sign Language Development Month by Month?
- Optimal Signs to Teach at Each Developmental Stage
- The Pre-Signing Period: 4 to 7 Months
- The Emergence Period: 8 to 12 Months
- Building Vocabulary: 13 to 18 Months
- The Transition to Speech: 18 to 24 Months
- Managing Expectations and Common Stalls
- Individual Variation and Realistic Timelines
- Looking Ahead: What Signing Builds
- Conclusion
What Happens in Baby Sign Language Development Month by Month?
The first few months of teaching baby sign language are primarily about exposure rather than production. From 4 to 6 months, babies are developing the visual tracking and attention skills needed to notice signs. Their motor control is not yet refined enough to form hand shapes, but they are absorbing far more than their still hands suggest. During these months, parents should focus on just two or three high-frequency signs like “milk,” “more,” and “eat,” using them consistently during daily routines without expecting anything back. Between 7 and 9 months, most babies enter a transition period. They begin showing recognition signs: looking toward the bottle when you sign “milk,” or opening their mouth when you sign “eat.” This receptive understanding is the foundation that productive signing builds upon.
Some early signers may produce approximations of signs during this window, though many will not. Babies who crawl early sometimes show slightly delayed signing because their motor focus is elsewhere. This is normal and not cause for concern. From 10 to 14 months, the productive phase typically begins. First signs are rarely perfect””a baby signing “more” might just clap or tap their chest instead of bringing fingertips together””but the meaning is clear from context. Once that first sign appears, others often follow within weeks. By 15 to 18 months, many signing babies have 10 to 25 signs, and by 24 months, some have built vocabularies exceeding 50 to 75 signs alongside their growing spoken word count.
Optimal Signs to Teach at Each Developmental Stage
Not all signs are equally suited to every age. In the early months, priority should go to signs that are highly motivating and occur frequently throughout the day. “Milk,” “more,” “eat,” and “all done” meet both criteria for most families. These signs also happen to be motorically simpler””they involve larger movements rather than intricate finger shapes, which matters for babies whose fine motor skills are still developing. However, if your baby shows particular interest in something else, follow that lead even if it seems unconventional. Some babies become fixated on ceiling fans, dogs, or birds well before food becomes motivating.
A baby who lights up every time the family cat walks by may sign “cat” as their first sign rather than “milk.” The emotional charge of the word matters more than its category. One limitation of rigid curricula is that they cannot account for your individual baby’s obsessions. As babies move into the 12- to 18-month range, they can handle more abstract signs like “help,” “hurt,” “where,” and emotion words. Their receptive vocabularies are exploding, and they can connect signs to objects or feelings that are not immediately present. This is also when signs for common animals, vehicles, and activities become useful. By 18 to 24 months, toddlers can learn signs for colors, sizes, and other descriptive words, though many families find that spoken language is taking over by this point.
The Pre-Signing Period: 4 to 7 Months
During the pre-signing period, your job is to build the foundation without expecting any return on investment. This can feel unrewarding, and many parents quit during these months because they see no evidence that their efforts are working. The evidence is there, but it is subtle: your baby’s eyes following your hands, their body stilling slightly when you sign during a familiar routine, a look of recognition when a sign appears in a predictable context. Consistency matters more than frequency during this phase. Signing “milk” every single time you offer a bottle or breast creates a reliable pattern your baby can learn from.
Signing the same word fifty times during one enthusiastic session teaches less than signing it five times daily for two weeks. Babies need repetition across varied contexts and times to form the association between hand movement and meaning. For example, a parent might sign “milk” while asking “Do you want milk?”, again while preparing the bottle, and once more as the baby begins drinking. That is three exposures in one routine, which happens four or five times per day. Over a month, that adds up to more than 400 consistent pairings of sign and meaning””exactly the kind of data a baby’s brain needs to crack the code.
The Emergence Period: 8 to 12 Months
This is when babies shift from passive observers to active participants, though the transition is often messier than parents expect. First signs are approximations. “Milk” might look like an opening and closing fist. “More” might look like clapping. “Eat” might involve fingers going toward the mouth but not touching. Parents who expect perfect ASL handshapes may not recognize these attempts for what they are. The tradeoff during this period is between adding new signs and reinforcing emerging ones. When a baby produces their first sign, the temptation is to celebrate and immediately introduce five more words.
This can backfire. The baby’s working memory is limited, and too many new signs can crowd out the fragile ones still being consolidated. A better approach is to add one new sign for every sign the baby is using confidently, keeping the ratio manageable. Babies in this period often sign inconsistently. They might sign “more” perfectly on Tuesday and then not produce it again until the following week. This is developmentally normal. The neural pathways are still being strengthened, and performance varies with mood, hunger, tiredness, and interest. Parents should respond to every attempt, even imperfect ones, while continuing to model the correct form themselves.
Building Vocabulary: 13 to 18 Months
By the second year, signing takes on a different character. Babies are no longer learning individual signs in isolation””they are building a communication system. Many babies begin combining signs with sounds or facial expressions, creating proto-sentences like signing “more” while saying “ba” for banana. This is a sign that language development is progressing normally, not that signing is replacing speech. The 13- to 18-month period often brings what researchers call the “vocabulary explosion” in signing. A baby who knew five signs at 12 months might know twenty by 15 months.
This happens because babies have cracked the symbolic code: they understand that everything has a name, and they want to know all of them. Parents often report that babies begin pointing at objects and looking expectantly, waiting for the sign. One challenge during this period is that signs and words sometimes compete for the baby’s output. A baby might sign “dog” one day and say “da” the next. This is not confusion””it is flexibility. The baby is experimenting with multiple channels of communication, which is exactly what we want. Parents should continue signing even as spoken words emerge, allowing the baby to choose their preferred mode for each communication.
The Transition to Speech: 18 to 24 Months
As spoken vocabulary grows, signing naturally diminishes for most children. This transition happens gradually rather than all at once. Babies typically drop signs for words they can say clearly while retaining signs for words that are harder to pronounce. “Help” and “hurt” often persist because the words are phonetically challenging, while “mama” and “ball” are replaced by speech early.
Some parents worry that this transition means their signing effort was wasted. The research suggests otherwise. Studies tracking children who signed as babies find lasting effects: slightly earlier spoken vocabulary development, better early literacy skills, and in some studies, modest IQ advantages that persist into elementary school. The benefits of signing appear to transfer to speech rather than competing with it. A practical example: A 20-month-old might sign “more” while clearly saying “juice,” creating a signed-spoken phrase before they have the grammatical ability to say “more juice.” This bridging function””using signs to extend what speech can accomplish””continues until spoken language catches up entirely, usually by age 2 to 2.5 years.
Managing Expectations and Common Stalls
Not every baby follows the textbook timeline. About 20 percent of babies do not produce their first sign until after 12 months, and a small percentage never sign despite months of consistent exposure. This does not necessarily indicate a problem. Some babies are simply more oriented toward spoken language and will talk early instead of signing first. Warning signs that warrant attention are different from normal signing delays. A baby who is not signing by 15 months but is babbling, making eye contact, responding to their name, and understanding spoken language is likely fine.
A baby who is not signing and also not meeting these other milestones should be evaluated by a developmental pediatrician. Signing delay alone is rarely concerning, but it can be one piece of a larger pattern worth investigating. Common reasons for stalled progress include inconsistency (signing only occasionally rather than at every opportunity), introducing too many signs at once, and not waiting long enough for responses. Babies need processing time. When you sign “milk,” wait at least 5 to 10 seconds before moving on. Many parents sign and immediately take action, never giving the baby a window to respond.
Individual Variation and Realistic Timelines
Two babies in the same family, taught by the same parent using the same methods, may produce their first signs months apart. Birth order, temperament, motor development timing, and simple individual variation all play roles. Second and third children sometimes sign later than firstborns because their older siblings interpret their needs, reducing motivation to communicate independently.
Temperament matters as well. Cautious babies who observe before acting may take longer to produce signs but often sign more accurately when they do. Bold, active babies may sign early but with sloppier approximations. Neither pattern predicts long-term outcomes.
Looking Ahead: What Signing Builds
The month-by-month journey of baby sign language is ultimately about more than the signs themselves. Families who sign together report stronger early communication bonds, reduced frustration during the pre-verbal period, and a foundation of intentional language interaction that continues after signing fades. Many parents find that the habits built during signing””narrating activities, waiting for responses, watching for communication attempts””persist into the toddler years and beyond.
The signs eventually disappear, replaced by words and sentences. What remains is a child who learned early that communication works, that their attempts to express themselves will be understood and responded to, and that language is a collaborative project between speaker and listener. Those lessons outlast the hand movements that taught them.
Conclusion
Baby sign language unfolds across a predictable timeline: exposure and modeling from 4 to 7 months, recognition and first approximations from 8 to 12 months, vocabulary building from 13 to 18 months, and gradual transition to speech from 18 to 24 months. Within this framework, individual babies vary widely in when they hit each milestone, and both early and late signing fall within normal ranges.
The practical approach is to start with three to five high-frequency signs around 6 months, maintain consistency across daily routines, celebrate approximations without demanding perfection, and add new signs gradually as your baby demonstrates understanding. Expect little visible progress for the first several months, recognize receptive understanding as progress even before productive signing appears, and trust that the investment of those early repetitions is building something real beneath the surface.