When do babies start laughing?

Experts explain what to look for in this baby milestone.

Zany faces, funny noises and zerberts galore. Parents of young babies will stop at nothing to try and get their baby to laugh for the first time. If your little one has yet to show you this instinctive reaction to happiness or excitement, here's what you need to know.

WHEN DO BABIES LAUGH?

You might hear the first laugh around four months, but keep in mind that it could also be sooner or later. "Generally around three to five months you might hear the first little one, and then usually a big belly laugh by six months," says pediatrician Jennifer Cross, from the NewYork-Presbyterian Komansky Children’s Hospital and Weill Cornell Medicine.

WHAT MILESTONES COME BEFORE LAUGHING?

According to Cross, you should first expect to see social milestones such as making eye contact and smiling, as well as making small noises like cooing. "Obviously laughing is generating sound, so you need to be gurgling and cooing a bit before you are really laughing," says Cross.

If you're hoping to get your baby to laugh by playing peek-a-boo, note that you might have to wait until at least seven months. "The milestone of object permanence starts at about seven months, which is when babies start to realize that you disappear for a minute but you are actually hiding, and oh, there you are coming back," says Cross. You can try this game with a younger baby but, as Cross says, "They might be amused but not really get it."

THINGS THAT MAKE BABY LAUGH

Be direct. Whether you're smiling, making funny faces or bringing in the goofy older sibling for backup, it's important to engage with a baby in a purposeful way, since, as Cross says, "little babies don't just laugh spontaneously." Her favorite tried-and-true trick? "Blowing on the belly always seems to make them laugh," she says. Eye contact is also extremely important. "Having them look at your face is really the start of social engagement, and babies seem to be predisposed to enjoying faces and wanting to interact with them," says Cross.

Stay close and go big. You also want to be sure you're within a foot or two of your child, since young babies may still experience blurriness when looking across a room. And, don't be afraid to bust out your silliest baby talk. "Use lots of expression and animation, and definitely over-exaggerate your movements and your sounds, so they pick up on the cues," says Cross, adding, "I'm not sure why some parents have heard they shouldn't talk to babies like they are babies — they absolutely should."

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Be a copycat. Imitating your baby is another way to encourage the back-and-forth interactions that are so important for social development (whether they spark a laugh or not). "Babies learn by what they see around them, so it's also a good idea to imitate, for example they smile, you smile. Also imitating them is a great way to show them oh, I can do something myself to engage this person. At first they won't imitate words, but they will imitate cooing, blowing raspberries and mouth movements as they explore what it is to make sounds," says Cross.

Limit screen time. Even if you think "Sesame Street" is hysterical, it's not going to have the same effect on a little one. "Face-to-face engagement is where we want to be, rather than two-dimensionally on a screen, and the evidence doesn't even support screens teaching things like colors or numbers, certainly not under the age of three," says Cross.

WHAT TO DO IF BABY ISN'T LAUGHING

According to Cross, you should let your pediatrician know if your baby isn't smiling by four months and if they are not demonstrating any kind of laugh by six months. You can make sure she is meeting her milestones for physical, social and emotional development by bringing her in for regular well visits.

Cross says she would likely start with tests to rule out issues with the eyes and ears before assessing for a developmental delay. "Every so often a baby might be born with a cataract so they really can't see, and all children should get a hearing screen in the nursery. Both of those are important to keep in the back of the mind," she says.