When Do Babies Start Laughing: The Question Behind the Question

Your baby has been laughing at you for weeks, and you've been doing the silliest things to earn it — the voice, the face, the theatrical peel of a banana. The laughter has felt like a conversation. What the research suggests is that it wasn't quite one, not yet. When do babies laugh for the first time is a different question from when babies first find something funny, and the gap between those two milestones turns out to be surprisingly interesting.

The one-sentence answer: Most babies produce their first laugh between three and four months of age, but laughing and genuinely understanding humor are separate developmental events roughly a month apart — which means that the laugh you're hearing right now tells you something specific about where your baby's brain is, not just that your face is funny.

A quick map of what's below:

• Why the "around four months" number is accurate but incomplete — and what it misses about how laughter actually develops
• The study that found four-month-olds laugh without independently getting the joke, and what five-month-olds can do that four-month-olds cannot
• How the things that make your baby laugh shift predictably over the first year — and why each shift is a readout of what the brain can now process
• Why babies laugh in their sleep, and what is actually happening when they do
• What the Navajo First Laugh Ceremony understands about this milestone that most parenting content does not
• When to mention laughter patterns to your pediatrician, and how to frame that conversation

If the one-sentence answer above is all you needed, you're set. If you want the mechanism behind each piece, keep reading.

Four Months Is When the Laugh Arrives — Five Months Is When It Means Something

Most babies first laugh between three and four months of age. This is well-established: Sroufe and Wunsch documented it in a landmark 1972 observational study of 150 infants, and Caspar Addyman's survey of more than 1,300 parents across 62 countries found an average first-laugh age of 3.5 months. The number is reliable. What it does not tell you is what that early laugh actually represents.

In 2018, Gina Mireault and Susan Crockenberg at Johnson State College ran two longitudinal studies to answer a more precise version of the question parents are actually asking when they search "when do babies laugh" — one following 60 infants at four, six, and eight months, the second following 53 infants at five, six, and seven months — to pinpoint exactly when babies stop just laughing and start genuinely understanding that something is funny. Each infant was shown a series of ordinary events and absurd versions of the same events, while a parent's facial expression was controlled as either laughing or completely neutral. The design separated two questions: does the baby find this funny on its own, or is the baby reading the parent's cue?

Four-month-olds laughed. But when the parent stayed neutral, they did not smile or laugh more at the absurd events than the ordinary ones. Something registered (their heart rates slowed measurably, an orienting response that signals "I noticed something is off") but they did not independently appraise the absurd event as humorous. Their laughter was still tied to the social context: to the parent's energy, to the playful voice, to the face doing something animated and warm.

Five-month-olds were different. In the second study, five-month-olds smiled and laughed at the absurd events even when their parent's face was completely neutral. They were no longer waiting for a cue. They were making their own assessment. The study, published in the British Journal of Developmental Psychology, is one of the very few to isolate this transition, and it changes what the milestone means: your baby's first real laughs at three to four months are a social act, a response to your warmth and playfulness. The laugh that emerges at five months and beyond is something more: evidence that your baby is building an internal model of how the world is supposed to work, noticing when it is violated, and deciding that is funny.

This is also the window where color vision kicks in. Our Color Contrast Cards are designed for exactly this stage — bold, progressively complex patterns built around how color processing develops between three and six months. A baby who was staring seriously at cards last month may start grinning at them now. Same cards, different brain.

What Makes Babies Laugh Changes Every Few Months — and That Is the Point

In 1972, Alan Sroufe and Joseph Wunsch observed 150 infants across their first year of life and documented a pattern that no parenting article since has fully described: the content of laughter changes on a roughly predictable schedule, and each change maps onto a new cognitive capacity the brain has just come online with.

At three to four months, the most reliable triggers are tactile and auditory. Tickling, gentle jiggles, raspberries blown on a belly, an exaggerated funny sound: these work because the nervous system is wired to respond to physical novelty, and the infant brain does not yet have the machinery to sustain a joke. The laughter here is partly reflex, partly the earliest version of social play. It feels like a conversation, and it is, but it is one where your baby is reading your energy rather than evaluating content.

Between five and seven months, visual and social incongruity starts working. Peekaboo becomes reliably funny at this stage not because the baby has "learned the game" but because the prefrontal circuits that hold a mental model of what should be there (your face) are now developed enough to register a mismatch when you hide. The laugh at the moment of reveal is the brain resolving a small prediction error in a safe, secure context. By six months, some babies begin producing what researchers describe as anticipatory laughter: they laugh just before you reappear, because they have already predicted it. That is a working memory event, and it is happening in the body of someone who cannot yet sit up unassisted.

Between seven and nine months, visual incongruity from familiar objects starts triggering laughter — the baby laughs when you put a cup on your head, or speak in a silly high voice, or hold a book upside down. Sroufe and Wunsch noted that these violations of familiar-object function are not funny before seven months, because the baby does not yet have a stable enough expectation about how the object should behave. Once that expectation forms, the violation is available as humor.

From nine to eleven months, babies begin making jokes. Vasu Reddy at the University of Portsmouth documented this phase in a series of observations: infants offering objects and then pulling them back, splashing deliberately when they have established a "no-splash" pattern, doing the thing you just told them not to do while watching your face for a reaction. This is proto-humor and it requires a rudimentary theory of mind, a sense that your expectation exists and can be deliberately violated. The same brain that figures out "if I drop this spoon, someone picks it up" is the brain that figures out "if I do the thing mom just said not to do, her face does something interesting." It all runs on the same wiring.

Now that you know what makes your baby laugh at each stage, you have a built-in cue for the five-month photo. All you need is this article and our Milestone Cards — the kind of designs that will make even you smile.

Why Babies Laugh in Their Sleep

"Baby first laugh in sleep" is one of the most common searches on this topic, and for good reason: newborns and young infants smile and sometimes laugh during sleep, often before any awake-state social laugh has appeared. Parents find this either charming or mildly unsettling and want to know what is happening.

The mechanism is not dreams. Babies in the first months of life lack the cognitive architecture for narrative dreaming. What they have is a dramatically different sleep structure than adults: where adults spend roughly 20 percent of sleep in REM, newborns spend closer to 50 percent. REM sleep in infants generates spontaneous neural activity in the brainstem and subcortical structures (regions that control facial muscle movement), producing the micro-expressions that look like smiles and, occasionally, brief laughs. This was documented by Maria Cecchini and colleagues in a 2011 paper in Infant Behavior and Development: neonatal smiles during active sleep (the infant precursor to adult REM) are endogenous expressions driven by internal neural firing, unrelated to social experience, unrelated to sensory input from the environment.

The sleep smiles and sleep giggles that appear in the first months are, in a very real sense, the nervous system rehearsing. The same motor programs that will later be deployed deliberately — in response to your face, in response to peekaboo, in response to a book held upside down — are being fired randomly during the heightened neural activity of REM sleep. The expression appears before the social use is available. For our guide to activities for a 3-month-old, we note that what you do during those first awake-window play sessions is providing the social scaffolding that will eventually make those same expressions available on demand.

The Navajo First Laugh Ceremony Understood Something Modern Research Confirms

The Navajo (Diné) have long marked a baby's first laugh as among the most significant early milestones, not the smile, not the first word, but the first genuine, unprompted laugh. The ceremony is called A'wee Chi'deedloh, loosely meaning "the baby laughed." Whoever is present and elicits that first laugh has the honor of hosting a small celebration, and the baby (with some assistance) distributes salt and small gifts to the gathered family. The gesture is understood as the baby's first act of generosity, and it symbolizes the child's full entry into the Diné community and into relationships of kinship and mutual responsibility.

Leighton and Kluckhohn documented this tradition in their foundational 1947 ethnography Children of the People, published by Harvard University Press. Caspar Addyman, who has spent years studying infant laughter at Goldsmiths, University of London, noted in a Teachwire interview that the Navajo tradition expects first laughs around three months — exactly where his worldwide survey placed the average.

The convergence is not coincidence. A tradition built across generations of close infant observation arrived at the same developmental window that controlled laboratory research later identified. And the meaning the Navajo assigned to it (the first laugh as the beginning of social reciprocity, the first evidence that the child has joined the human conversation) maps almost precisely onto what the research described above shows: the transition from reactive laughing to independent social evaluation. When do babies laugh in a way that means they have fully joined the social world? The Navajo ceremony says the same thing the Mireault data says: somewhere around five months, something shifts. Your baby's first laugh is not just adorable. It is, in the language of developmental science, the first sign that your baby is building the model of social expectation that everything else (humor, language, theory of mind) will eventually run on.

The activities for a 4-month-old guide covers what this window looks like in daily play, including why peekaboo is so effective precisely because it exploits prediction and violation — the same mechanism the Mireault research identified as the engine of infant humor.

Laughter Is Also 10 to 16 Million Years Old

Tickling is, by a wide margin, the most reliable method for producing infant laughter across cultures and across the first year. Addyman found it was the most common answer in his worldwide survey when parents were asked what is guaranteed to make their baby laugh. This is not accidental.

In 2009, Marina Davila Ross, Michael Owren, and Elke Zimmermann published a study in Current Biology in which they recorded tickle-induced vocalizations from 21 great apes — orangutans, gorillas, chimpanzees, and bonobos — and from three human infants being tickled by their mothers, then built a phylogenetic tree from the acoustic features. What they found was that the evolutionary branches of laughter-like vocalization diverge between humans and the other great apes roughly 10 to 16 million years ago. Tickle-laughter, in other words, is an ancient social-bonding signal shared across the great ape lineage, not a learned cultural behavior, but a deep-wired play communication that predates language, predates tools, predates essentially every distinctly human characteristic.

When you tickle your three-month-old and your baby folds into that first full-body laugh, you are activating a neural circuit that your common ancestor with chimpanzees already had. That does not make it less special. It makes it much more so. It means that laughing together (the parent making a silly face, the baby folding and laughing, the parent laughing back) is one of the most conserved social behaviors in primate evolution. For our full overview of what the first three to six months looks like developmentally, see the guide to when babies start smiling and our cluster on activities for a 6-month-old.

How to Make a Baby Laugh (Framed Through the Research)

The generic tips list here — peekaboo, tickles, silly faces — is accurate. What the research adds is a framework for why each one works at the age it works, which means you can calibrate your approach rather than just trying everything and hoping. Understanding when do babies laugh at different types of stimuli also helps you know when to escalate the complexity of play.

Before five months, laughter is most reliably triggered by your energy and physical play. Animated facial expressions, responsive cooing, tickles, and gentle jiggles work because the infant nervous system is tuned to the parent's emotional cues. Match your energy to what you see the baby tracking. If the baby is watching your face intently, a slow exaggerated smile often triggers a smile back; a sudden playful sound layered on top of that can tip it into a laugh. Our guide to activities for a 5-month-old goes deeper on the specific play structures that work best during the social-humor transition window.

From five months onward, add incongruity and violation-of-expectation. The same peekaboo game now has a second layer: your baby is not just responding to the reveal, but predicting it. You can test this: if the laugh comes just before you reappear, you are watching memory and anticipation in real time. A book held upside down, a spoon put in an unusual place, a funny sound at an unexpected moment — these start working here because the brain is now storing enough expectations to notice and enjoy violations.

From seven to nine months, the humor becomes more sophisticated. Babies this age laugh at violations of familiar-object function (what Sroufe and Wunsch described in 1972), enjoy causing their own silly moments, and begin to test whether causing a response in you is funny. When your baby does the thing you just gently discouraged and then looks at your face with what looks very much like a smirk, that baby is not being defiant. That is a joke.

One structural note from the Mireault research: parent laughter did not directly cause infant laughter at any age studied. What parent laughter did do was capture four-month-olds' attention. It signaled that something worth attending to had happened. The implication is that your enthusiastic reaction after the baby laughs is part of what teaches your baby that laughter is a communicative act, a joint event, something that goes between people. Responding to the laugh with warmth and attention, rather than performance, is what builds the social scaffolding a baby needs for humor to develop further.

When to Mention Laughing Patterns to Your Pediatrician

Most babies laugh by four months. By six to seven months, laughing in response to social play, faces, and simple games should be consistent. If your baby reaches six months without laughing, or does not consistently respond to sounds, it is worth mentioning at the next well visit — not as an emergency, but as a useful data point for your pediatrician. Laughter relies on hearing, on social awareness, and on visual tracking all working together, and a pediatrician who knows you've noticed an absence can make a more informed assessment.

Temperament matters here. Some babies are genuinely more serious. They observe, they analyze, they do not produce as many overt laughs as other babies the same age. As long as they are tracking faces, responding to social interaction with expressions and vocalizations, and meeting other milestones in the expected windows, a quieter laugh pattern is not a flag.

If a baby who was laughing stops, regresses, or stops responding consistently to social interaction, that is the clearest reason to call rather than wait for the next scheduled visit. Regression in any milestone is the kind of pattern a pediatrician will want to look at — not just in isolation, but alongside the full picture of development. See also our overview of when babies start talking, which covers the broader arc from early vocalizations to first words and why the connections between laughter, babbling, and language matter.