Opinion | What a Baby’s Laugh Actually Tells Us – The New York Times

The signature belly laughs seen in the video above are involuntary, bursting forth during genuine, uncontrollable amusement. This type of laughter is driven by the brain’s limbic system, structures crucial for emotion, memory and motivation. But by 6 months, our lab has found, infants can intentionally produce a laugh. This ability comes not from the limbic system but from the brain’s language areas and emerges at the same time as babbling. Six-month-olds will deploy laughter to prolong a game of peekaboo or to signal a desire to join in.

But laughter does more than increase pleasurable social contact; infant laughter, especially when it occurs in response to humor, signals a cognitive achievement. When an infant laughs at Dad wearing a spoon as a mustache, it reveals the baby’s knowledge about spoons and mustaches, as well as about the person wearing it.

Even before her first birthday, the 8-month-old girl in the video below recognizes a “benign incongruity” — an unexpected yet harmless event — that does not align with her typical experience, in this case a stuffed toy repeatedly taking flight from atop her mother’s head.

Yet, beyond recognizing the incongruity, perceiving it as funny requires babies to resolve or make sense of it, by either anticipating or identifying the cause of these unusually strange experiences.

In verbal jokes, incongruity resolution occurs the moment the punchline makes sense, which is often marked by laughter.

the ability to tease reveals infants’ insight into others’ minds and how to provoke them. Teasing requires knowing how to engage another person in a safe, playful interaction, including how and how much to push a set boundary.

In the video below, a 14-month-old boy offers food to his dad, then suddenly reneges, feeding himself instead to entertain his laughing parents. A 9-month-old deliberately approaches a playfully forbidden plant. A 10-month-old continues to reach for the forbidden cat food bowl in full sight of his grandmother who playfully prohibits him with “uh-uh-uh,” an utterance he has also added to the game.

In each example, notice the baby checking with the adult before carrying out the prohibited act, their eyebrows raised as if asking, “But if I do, what will you do?” Their smiling signals they are engaging their play partner with a conscious violation, as though the playfulness is less about the cat food or plant, for example, than the other person’s reaction.

That these cognitive skills — incongruity resolution and insight into others’ minds involved in teasing — appear before a child’s first birthday and before other major milestones like walking or talking, suggests that nature preserved, if not prioritized, laughter and humor in the service of development.

Babies’ laughter, especially in response to surprising or absurd events, reflects their curiosity, understanding and drive to connect with the people in their lives.
— Read on www.nytimes.com/2026/02/04/opinion/baby-laugh-developmental-milestone.html