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Baby Smiling in His/Her Sleep? Here’s Why!


Is your baby smiling while sleeping? Here’s why!

Babies give parents many of their most heartwarming moments in life. The first word and first step are two of the well-known moments that parents see coming from a mile away. You wait for those moments. Other moments are more subtle, like the sight of your infant gently smiling in his or her sleep.

This moment is one of the more veiled ones that sneak up on you and make your heart smile in a way that it never has before. When you go in to check on the little one and find baby smiling in their sleep, you just know that something special has to be happening over there.

What exactly is happening over there? Formally known as Neonatal smiling, baby smiling in their sleep is a real event to take in. What’s the science behind it? What is your little critter smiling about now? That may be the first question that crosses your mind when you see that cute little infant grin: What’s my baby smiling about? Unfortunately no one can no exactly for sure why a particular baby smiling in sleep moment happens, but we have learned a surprisingly full body of information about the infant smile. Let’s dive in.

Infant Smiling

Babies don’t just smile in their sleep. Their smiling mechanisms evolve surprisingly quickly, giving them the ability to smile in social situations by the age of two months. You’ve likely already noticed this adorable waking smile, where baby loves the sights and sounds of your company and begins to respond with smiles to your gestures and baby talk.

The same mechanisms at play in the waking smile probably play a part in that restful smile as well, only the restful smile is just that much more adorable because baby doesn’t even know baby is smiling in sleep. There are three primary types of smiles among infants: Social, reflexive, and responsive.

  • Social smiles are very important because they show that the baby is sharing with you an emotion of their own
  • Reflexive smiles simply happen, and there’s much science behind them we just don’t understand
  • Responsive smiles often occur in sleep, too, and are signify that there’s a sensory event your baby is responding to

Baby smiling in sleep falls under reflexive or responsive smiles. When it’s a responsive smile, they might be hearing a noise in the environment while they sleep and in turn smile in response. If it’s reflexive, this can occur extremely early in life, even the first few days of life, and these are the most perplexing smiles to understand because they haven’t yet developed enough to respond to anything in the environment with an emotional smile, and yet there they are, smiling away!

Let’s Smile About Science

Of everything, it’s the reflexive smile that has the most science behind it and seems to indicate that babies are literally born with the ability to smile. They’re not smiling at you in their sleep, and they’re not necessarily responding to anything, but the smile is there. Scientists have noticed that infants typically smile most during the REM stage of sleep. This is the stage of sleep where dreaming occurs. Dreams and rapid eye movements occur during this stage of sleep, and it’s possible that your little bundle of joy is smiling about a dream they’re having.

Less scientific is when baby is smiling in sleep because of a physical event going on, such as passing gas. Whether this falls under responsive or reflexive smile is up for debate, but one thing is for certain: Babies sometimes do smile when they’re passing gas in their sleep. There are a lot of emotional developments going on while baby is sleeping, so this can trigger one of those absolutely adorable baby smiling in sleep moments. Those moments are shared between infants and parents alike, all over the world, sometimes for the first time, sometimes for the millionth time, but always for a heartwarming time.

Is My Baby Dreaming?

Keep in mind that there is a lot of scientific debate about why babies smile in their sleep. Some pediatric specialists believe that babies can indeed dream, and other specialists who have studied the subject claim they can not.

That’s part of the fun of science. There’s a constant debate going on, and we get a very clear picture from both sides and then get to make up our minds as parents as to what we believe. The developing human brain is in a constant state of flux, constantly evolving into something more, and this is especially true of infants.

Their rapidly developing brains are a mystery to even the most veteran scientists, but it’s interesting to read the opinions of all experts.

How Those sleepy Smiles Leave Their Mark

Just about everything your new baby does will be special to you. Anyone who’s had a child knows this. Some things are just a little more special than others, and catching a glimpse of baby smiling in sleep can certainly be one of those moments that catches you off guard and leaves a mark on your heart.

While there is a lot of disagreement over just what causes babies to smile in their sleep – one baby myth insists that they’re smiling at angels – we can all agree that seeing baby smiling in sleep is one of those amazing moments you share with your children.

Since the smile occurs during REM sleep, it’s possible that your little one is smiling over a dream they’re having about you. Even though they can’t wake up and tell you that, it’s something you might feel in your heart. And that will make you smile at them right back.

Making Your Baby Smile More During Sleep

Smiles based on sensory experience do happen in sleep as well, so if you want to inspire more of those smiles, you might want a gentle music mobile playing while they’re sleeping. Perhaps the most special thing about baby smiling in sleep is that it’s completely out of the blue, spontaneous, and there’s nothing you can for sure do to make it happen.

You just have to wait for the moment to occur and savor it. Many parents like to take pictures of their infants smiling in their sleep. That’s one way to savor the moment forever, and of course, you can even share this special moment with your friends and family on social media.

Neonatal smiling continues to be one of those less often talked about parenting moments. Most babies are going to eventually give you that big grin in their sleep, and when they do, you’re going to remember it forever. There’s nothing quite as sweet in all the world as a smiling infant.

Is it a reflex?

Baby smiling in sleep may be reflexive at times, but your smile will most definitely be responsive, as you stare at your little creation and marvel at how even the simplest things bring a smile to your heart.

Science continues to study the mechanisms behind those precious sleep smiles, but for now we’ve got some basic information that gives us a general idea about why baby is smiling in sleep and what you might be able to do to enjoy those moments more (grab the camera at least once).


As more scientists study smiling in infants, we’ll know even more in the days to come. For now, though, you’ve only got to know that babies do smile in their sleep. It’s a precious thing to behold, and it’s something that you can share with your infant each and every time they smile, whether it’s because they’re dreaming of something, reflexively smiling, or simply passing gas and apparently getting a kick out of it.

The world of babies will forever be fascinating to learn about because they are the purest form of human on earth. They’re constantly developing and learning new things, as the human mind takes shape. That you get to share in that experience should make you smile in your sleep sometimes, too.

2 thoughts on “Baby Smiling in His/Her Sleep? Here’s Why!”

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