Why Do Babies Laugh in Their Sleep?

Few things catch you off guard like hearing a soft giggle from the cot when the room is quiet. Moments of babies laughing in their sleep or newborns smiling in their sleep are usually a normal part of how an infant’s brain and body practise new skills as they grow. Often it’s simply a sign of active sleep, not a response to anything upsetting. This article will explain what may cause sleep laughs, how it changes with age, and the rare signs worth discussing with a health professional.

Why Do Babies Laugh in Their Sleep?

Most sleep giggles happen during active sleep (REM sleep), a lighter stage when a baby’s brain is especially busy. Newborns spend approximately 50% of their sleep in active (REM) sleep, compared with around 20 - 25% for adults, so there’s far more time for tiny movements, noises, and changing facial expressions. During baby REM sleep, the brain helps process new sensations, consolidate early experiences, and practise motor patterns - activity that can trigger reflexive smiles, little laughs, and other vocalisations. At this stage, sleep laughter isn’t a response to a joke or a complex dream story; infants don’t yet have the cognitive maturity for that. It’s better understood as a neurological reflex - the brain briefly ‘misfires’ a laugh response as it maps emotions and movement pathways. Over time, these spontaneous expressions may also help strengthen the facial muscles that babies later use for social smiling and laughing while awake.

Is it the same for newborns and older babies?

In the early weeks, why newborns laugh in their sleep is usually simple: it’s almost entirely reflexive. The very first smiles can appear during active sleep before a baby produces a social smile while awake. A newborn’s (0 - 3 months) face may look busy during this stage - twitching, making sucking motions, frowning, and smiling - these are typical newborn sleep behaviours rather than reactions to something funny. As babies grow (around 3 - 6 months and beyond), laughter and smiling both awake and asleep can become richer. Social smiling often shows up around 6 - 8 weeks, and first laughs commonly appear around 3 - 4 months. Once a baby can laugh freely while awake, they may also laugh more expressively in their sleep - especially after a day full of faces, voices, and play. You can learn more about when do babies start laughing in our milestone guide.

Why does my baby laugh while falling asleep?

You may notice small grins or soft giggles as your baby drifts off. During the transition from wakefulness to sleep (the hypnagogic phase), babies can smile, twitch, and vocalise - especially in the first month. These early ‘sleep smiles’ are reflexes, not emotional reactions, and they often appear before social smiles show up while awake. So if you’ve seen newborns smiling in their sleep in those first weeks, it’s usually a normal part of newborn development. If you’re curious about when social smiles typically begin - and why babies laugh while falling asleep sometimes looks so expressive - see our guide on when do babies start smiling.

Are there any signs I should watch out for?

In the vast majority of cases, sleep laughter is completely benign - and it’s often just a sign of an active, developing brain. Still, it can help to know what to look for if something doesn’t seem quite like your baby’s usual sounds.

Very rarely, uncontrolled laughter can be linked to a type of focal seizure called a gelastic seizure. Epilepsy Action UK describes these seizures as very rare (affecting 1 in 1,000 children with epilepsy) and notes that the laughter is not caused by happiness or joy. It can sound hollow or mechanical, feel ‘out of place’, and the episode typically stops suddenly, often lasting under 30 seconds.

If you notice laughter that sounds distinctly unlike your baby’s normal laugh, repeated episodes that look the same each time, or your baby seems confused or unusually tired afterwards, speak to your GP or health visitor for advice. If it helps, note when it happens and how your baby seems before and after. These baby laughing in sleep red flags are uncommon - but checking in is the right move if you’re unsure. Most of the time, though, a sleeping giggle is simply part of healthy neurological development.

The bottom line

Hearing babies laughing in their sleep is usually a lovely sign of a busy, growing brain. In most cases, these giggles and smiles happen during lighter sleep stages and are part of normal development. Enjoy the moment if you can - those early weeks pass quickly, even on the tired nights. If you’d like practical ways to support more settled nights, you can find gentle tips to help your baby sleep, and it’s always worth reviewing safe sleep basics with safe sleep for babies. And if your baby’s sleep suddenly becomes more disrupted for a period, it can help to read about sleep regression.