What Makes Babies Laugh?

Humor has always been a matter of personal taste. While some enjoy the physical antics of Jim Carrey, others may prefer the dry wit of Albert Brooks.

Babies, naturally, aren't ones for subtlety. Making goofy faces, tickling their little feet, or playing endless rounds of peek-a-boo—where you pretend to vanish—are all surefire ways to elicit a giggle. But why do they laugh? Is it because they think their parents are amusing, or is it a simple reflex? Are they processing humor, or is it just a means of socializing? Could baby laughter simply be their way of saying, 'Hey, keep your eyes on me'?

We asked several babies, but they didn’t respond. (In many cases, a loaded diaper cut the questioning short.) Thankfully, a number of researchers have delved deeply into what babies find amusing. 'Nearly all babies are laughing by the time they reach 4 months,' says Gina Mireault, a professor of psychology in the behavioral sciences department at Northern Vermont University, in an interview with Mytour.

However, Mireault points out that both adults and babies tend to have a common misconception about humor: 'It doesn’t have to be linked to something inherently funny.'

From Smiles to Laughter

In the early stages of their lives, babies are mostly nonverbal, communicating through coos and babbles. Smiling, laughing, and crying are essential for engaging with the world around them. You’re unlikely to see a baby laughing by herself. 'It’s a social reaction,' says Mireault. 'Another person is the necessary component.'

Babies generally begin smiling between 6 and 12 weeks. By 3 to 4 months, they start laughing at physical actions like tickling, raspberries, or being bounced on a caregiver's knee. (In a 2014 study led by developmental psychologist Caspar Addyman at the Goldsmiths InfantLab at the University of London, parents noted that tickling was the most effective way to elicit laughter.) By 5 to 6 months, babies start to grasp the basic principle of humor—a twist on reality. Once they understand typical human behavior, they will giggle at exaggerated features like large eyes, puffed cheeks, and squeaky voices.

'It often involves what my colleagues call “clowning,”' Mireault explains. 'This can include things like wearing an oversized hat, a large bow tie, funny voices, or walking in an unusual way.' Babies find these breaches of social norms amusing because they develop expectations of how people usually behave. For example, when you pretend to be a kangaroo, you’re breaking those expectations, which is what makes them laugh.

'Surprise is a crucial element of humor,' says Mireault. 'There are two main theories: the Arousal-Safety hypothesis and the Benign Violation Theory. Essentially, they are the same idea. The theory suggests that humor that involves surprise is seen as non-threatening.'

When you hand your child a stuffed animal, they expect it to be there. If you unexpectedly drop it on the floor, this change in situation is likely to make them laugh. The key is the element of familiarity and playful intent. A smiling adult dropping it will be funny, but a stranger angrily throwing it won’t. Even Charles Darwin recognized this, noting in his 1872 book, The Expression of the Emotions in Man and Animals, that a child would 'scream in fear' if tickled by a stranger.

There are exceptions. In London, children’s theater directors Sarah Argent and Kevin Lewis have created several plays for babies 6 months and older, collaborating with Caspar Addyman and using research from the InfantLab. Productions like Out of the Blue and Shake, Rattle, and Roll were designed with an understanding of babies' natural fear of strangers. Performer Maisie Whitehead 'met' the babies at the start of Shake, Rattle, and Roll, singing to them to help them get comfortable with her. Throughout the show, Whitehead pretended to 'wobble' and lose her balance, which captivated the babies.

For Lewis, what stood out was the idea that a baby’s laugh can serve as a form of control. 'Laughter becomes a tool of power,' Lewis explains to Mytour. 'If I laugh, the big person repeats the action again and again. I can keep making them do it, prolonging my enjoyment, and I’m in control!' In this sense, babies are using laughter as a form of manipulation.

Why Babies Love Peek-a-Boo

Babies are also sensitive to intention. If you pretend to drop something and say 'ha, ha,' the baby will likely giggle. But if you say 'uh-oh' and act concerned, the baby will interpret it as a serious event. Exaggerated reactions like dropping objects were, in fact, a key feature in Argent's productions, sparking uncontrollable giggles in babies.

However, there’s a limit to how long such actions remain amusing, as babies will soon realize that the unexpected—like tossing a stuffed animal—is now predictable. As Mireault puts it, 'Babies aren’t foolish. They won’t find it endlessly funny.'

As babies learn more about the world, caregivers can begin to defy their expectations. But there’s one misunderstanding that consistently leads to a guaranteed laugh, without the need for the cheap trick of tickling: peek-a-boo.

There are several reasons why peek-a-boo is so effective. One explanation is based on a concept introduced by Swiss psychologist Jean Piaget, known as object permanence. This is the idea that something out of sight still exists.

For babies, the presence of a physical object is determined by whether it's visible. 'If you hide something, like car keys, from a 6-month-old by covering them up, the baby won’t search for them,' Mireault explains. The baby cannot yet comprehend that the keys are simply hidden.

The same principle applies to faces. When a parent covers their face with their hands, its sudden reappearance brings an element of surprise. As Mireault puts it, 'When you pop up again, it's like, ‘Wow, where did you come from?’'

Peek-a-boo is also a hit with babies because it introduces that shift in reality—big eyes and funny faces. However, by the time they reach 8 or 9 months, babies understand object permanence. If a parent leaves the room, the baby may become upset, recognizing that the adult is in another room, rather than simply disappearing.

That doesn’t mean peek-a-boo loses its charm. Babies may still find it funny, either from the fulfillment of their expectation—seeing their parent reappear—or from hiding themselves. As they grow older, the laughter may become less genuine. 'Babies can fake laugh at 6 months,' says Mireault. 'They can laugh to get attention. They start babbling and gain vocal control, using voluntary laughter, like when someone says, ‘Ha, ha, ha,’ and it doesn’t sound entirely authentic. It's just a nice social gesture.'

It’s unsettling to imagine that a comedian who is considered a genius by a 4-month-old might be seen as a washed-up Vegas performer by 6 months, earning only a few polite chuckles. According to Mireault, 'When babies laugh, they’re saying, ‘This isn’t as funny as it used to be, but I still want to keep playing, so show me something new.’'

Babies' Evolving Sense of Humor

As babies grow into toddlers, they begin to understand different forms of humor. Between 7 and 9 months, they start to find humor in contradictions. Put a hat on a dog and watch them laugh. By 12 months, they may look at a cup and call it a spoon, or they may giggle at an adult doing the same thing.

But the true milestone in a baby’s sense of humor may come when they start trying to make others laugh. By 5 months, babies have developed enough motor control to hold up their own stinky feet instead of waiting for a parent to do it. At 8 months, they begin to tease. 'This shows they understand that others can be tricked,' Mireault explains. 'They might offer you car keys and then pull them away just as you’re about to grab them.'

This goes beyond humor. It demonstrates a theory of mind—the understanding that other people have their own thoughts, beliefs, and expectations. While funny faces may seem simple, humor is a cognitive challenge that supports a baby’s development, eventually helping them hold onto the car keys for themselves.