You’ve probably been doing it for weeks. You make the "pffft" sound on their tummy. You play peek-a-boo until your arms ache. You might even be dancing around the living room like a total maniac, hoping for just one tiny giggle. Then, suddenly, it happens. A real, vocalized chortle that sounds like pure magic.
But when do babies start laughing out loud exactly?
Most parents are told to expect it around month four. Honestly, though, babies don't read the manuals. Development is messy. It’s inconsistent. While one infant might be belly-laughing at a family dog at 12 weeks, another might wait until they are nearly half a year old to find anything remotely funny. This isn't just about "humor"—it’s a massive leap in cognitive and physical development. Your baby has to coordinate their breath, their vocal cords, and the social understanding that this thing you are doing is meant to be a shared moment of joy.
The Science Behind the First Giggle
Before the big "out loud" laugh, there are the "social smiles." You probably saw those around two months. Pediatricians like those at the Mayo Clinic note that these smiles are the foundation. Before that, those little smirks you saw during sleep? Usually just gas or a reflex. Sorry to burst the bubble.
Laughing is a whole different beast. It requires a sophisticated level of "joint attention." This means the baby knows you are looking at them, they are looking at you, and you are both looking at a third thing—like a squeaky toy. According to researcher Caspar Addyman, who runs the Baby Laughter Project at Birkbeck, University of London, laughter is a deep tool for connection. His research involves thousands of parents globally, and he’s found that the very first laughs are often a response to physical sensations. Think tickling or the "I'm gonna get you" game.
It’s about tension and release.
Imagine you’re four months old. Your mom hides her face. Where did she go? That’s a tiny bit stressful. Then—BAM—she’s back! The stress evaporates, and the relief comes out as a rhythmic, vocalized sound. That’s the laugh.
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When do babies start laughing out loud if they hit milestones early?
If you’re seeing it at three months, you’ve got an early bloomer. It’s rare, but it happens. Usually, these early laughs are very quiet. They sound more like a sharp exhale or a series of rhythmic "huffs."
Don't mistake a "coo" for a laugh. Cooing is melodic and vowel-heavy. A laugh is percussive. If your baby is three months old and making a "ha-ha" sound, they are essentially practicing for the real thing. It’s like they are tuning an instrument before the concert starts.
The four-month peak
For the vast majority, the four-month mark is the sweet spot. By this time, the American Academy of Pediatrics (AAP) notes that babies are becoming more socially engaged. They start to realize that their actions have reactions. If they laugh, you laugh. If you laugh, they keep going. It’s the world’s best feedback loop.
At this stage, the laughter is almost entirely triggered by touch and sound.
- Blowing raspberries on the neck.
- The sound of a zipper.
- High-pitched "parentese" voices.
- Gentle bouncing.
Why some babies take their time
If your baby is five or six months old and still hasn't given you a "belly laugh," stop scrolling through those "perfect" parenting forums. It’s okay. Seriously.
Temperament plays a huge role. Some babies are observers. They are the "thinkers" who want to analyze the situation before they react. They might smile broadly and kick their legs to show joy, but they just aren't vocalizing it yet. It doesn't mean they aren't happy. It just means their "out loud" volume is still muted.
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There are also physical factors. A baby who is dealing with severe reflux or ear infections might be too preoccupied with physical discomfort to find your "peek-a-boo" routine particularly hilarious. If they are hitting other milestones—like following objects with their eyes, reaching for toys, and smiling back at you—the laugh will come.
What actually makes them laugh? (The Peek-a-Boo Mystery)
Why is peek-a-boo the gold standard for getting a baby to laugh out loud? It’s because it plays with a concept called object permanence.
Very young babies think that if they can't see you, you have ceased to exist. Around four to six months, they start to realize you’re still there behind your hands. When you reveal yourself, it confirms their theory. It’s a "eureka" moment. They are literally laughing at their own growing intelligence.
But it’s not just peek-a-boo. You might find your baby laughs at:
- The dog barking (the suddenness is funny once they aren't scared of it).
- The sound of water splashing in the tub.
- Siblings jumping up and down. Kids are often better at making babies laugh than adults are because they are less predictable.
- Sneezing. For some reason, a loud "achoo!" is the pinnacle of comedy for a 5-month-old.
Developmental Red Flags: When to call the doctor
While every baby has their own timeline, there are a few things to watch for. If your baby is six months old and has never made eye contact, doesn't smile at you, or doesn't react to loud noises, that’s worth a conversation with your pediatrician.
The concern isn't necessarily the lack of laughter itself, but the lack of "social engagement." Laughter is just one part of the social communication package. If the other parts (eye contact, babbling, responding to their name) are missing, a doctor might want to check their hearing or look for early signs of developmental delays.
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But if they are a happy, smiling baby who just happens to be "the strong silent type"? They’re probably just fine.
How to encourage the first laugh without being annoying
You can’t force a laugh. If you try too hard, you’ll probably just overstimulate them, which leads to crying, not giggling. There’s a fine line between "entertainer" and "menace."
Try these instead:
- The Wait: Perform an action, like popping a bubble, and then wait. Give them time to process the "joke."
- Physical Comedy: Babies love exaggerated movements. Lean in close, then pull back quickly.
- The Power of Sound: Use weird clicking noises or popping sounds with your mouth.
- Tactile Play: Lightly blow on their hair or tickle the bottom of their feet.
The transition from physical to cognitive humor
As they get closer to 9 or 10 months, the "why" behind the laugh changes. They start to laugh at things that are "wrong." If you put a bowl on your head like a hat, an older baby might laugh because they know bowls aren't hats.
This is a huge deal! It shows they have a mental model of how the world is supposed to work. When you break the rules of the world, it’s funny. You’ve gone from being a source of comfort to being a source of entertainment.
Real-world expectations for parents
Social media is a liar. You see videos of babies doubling over with laughter at a piece of paper being ripped. Those moments are fleeting. Most of the time, your baby will give you a quick "ha!" and then go back to staring intently at a dust mote in the air.
Don't judge your parenting—or your baby’s brain—by the frequency of their laughter.
Also, keep in mind that babies get "burned out" on jokes. What was hilarious at 10:00 AM might be irritating at 4:00 PM when they are tired. Respect their boundaries. If they turn their head away or start fussing, the comedy show is over for the day.
Actionable Next Steps for Parents
- Audit the environment: If you’re trying to get a laugh, make sure the room isn't too loud or bright. A calm baby is more likely to find humor in the small things.
- Track the "pre-laughs": Notice if your baby is breathing faster or widening their eyes when you play. These are signs they are close to a vocal laugh.
- Check the calendar: If your baby was born prematurely, use their "adjusted age" for milestones. A baby born two months early might not laugh out loud until they are six months old (which is four months adjusted).
- Focus on the smile: If the vocalization hasn't happened yet, cherish the social smile. It’s the same emotional connection, just without the sound effects.
- Talk to your pediatrician: Use the 6-month checkup to mention any concerns about social milestones, but don't lose sleep over a lack of giggles if they are otherwise engaged and happy.