Over the course of 12 months, your baby's gummy grins will transform into ways of expressing pleasure, communicating with you and developing a sense of humor. Here are those stages in detail.
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baby smiling
Credit: Alexandra Grablewski

0-6 Weeks: Reflexive Smile

You'll spot your newborn's first grin when he's asleep. You'll see him twitch, startle, and -- is that a smile? "During REM sleep your baby's body goes through physiological changes that activate certain reflexes, and one of those is a smile," says Pamela Garcy, PhD, a clinical psychologist in Dallas. At this point it's probably just a physical reaction, not an emotional sign.

6-8 Weeks: Responsive Smile

As your baby grows, she'll start to smile at things she finds pleasurable -- cuddles, voices, and faces. But don't expect too much at this stage. Her smile is a reaction to sensory experiences, not a social response. "You might like to think this smile is some sort of acknowledgment that you are the best mom in the world," says Charlotte Cowan, MD, a pediatrician in Boston. Of course you are! But these smiles aren't proof of it right now. "Your baby doesn't have a clear sense yet of who you are."

Still, you can try to encourage a smile. "You'll learn what noises and expressions get her to respond," says Julie Segal, MD, a pediatrician at Atlanta's Northside Hospital. Give your baby plenty of opportunities to study your face while you talk gently to her. Imitate her expressions, and she may start to imitate yours.

2-3 Months: Social Smile

Up until now, your baby's smiles have been internal reactions to things that catch his attention. Not anymore: At this stage, he wants to connect. Your baby will smile when he sees you and will react when you make silly sounds (try mooing, oinking, and beeping). He'll also learn that he can get a reaction from you by smiling -- not just by crying. The gurgling, the grunting, the strange humming are all attempts by your baby to express himself. Now there's no question. You're his favorite. "He'll squeal and laugh when he plays with you," says Mary Ellen Renna, MD, a pediatrician in Woodbury, New York. He'll also respond to you by getting his whole body in on the act -- moving his arms and legs for emphasis.

Remember, though, that your baby won't always smile when you want him to -- and that he also has to express other emotions. But if he hasn't smiled at all by 12 weeks, tell your pediatrician so that he can check for developmental delays.

About 6 Months: Undiscriminating Smile

While all babies develop at their own pace -- and some babies are just a lot more smiley than others -- midway into your child's first year, she'll most likely be a smiling expert. "Six-month-old babies grin at you no matter what you do," says Dr. Cowan.

About 9 Months: Selective Smile

This is the age when your baby starts to know you as special and distinct from other people, but there's a downside to that: Stranger anxiety sets in. Your formerly friendly baby is likely to stop smiling at strangers. While it can be disappointing that your baby doesn't "perform" quite as well, distinguishing faces is actually a sign of healthy development.

Also worth noting: Because your baby's sense of object permanence is stronger -- he knows that something exists even when he can't see it -- you can encourage him to smile by playing peekaboo. "Now you see it, now you don't" is the ultimate laugh-getter at 9 months.

About 12 Months: A Sense of Humor

As your baby starts to develop language skills, her sense of humor also emerges. "Babies this age laugh and laugh if you make silly noises," says Dr. Cowan. When your baby thinks something is funny, she wants to get a reaction out of you, too, so laugh along with her. Drop something on the floor, or make a funny face -- she'll find it hysterical. "Surprise is a big element in making babies laugh at 12 months," says Dr. Garcy. "Put your baby on your knees, sing a song, and then gently let her drop a bit." Take advantage of this fun stage; it's not every day you find someone who thinks you're the most hilarious person on earth!

Parents Respond: What Makes Babies Laugh?

When I sing to her in my mock opera voice. The rest of my family hates my silly singing, but my daughter, Cadence, loves it.--Julie M.; St. Charles, Missouri

I play peekaboo with my breastfeeding cover-up -- Andrew loves that!--Danielle L.; New York, New York

I jump up and down -- as simple as that sounds, it makes Phoebe laugh in fits.--Jenny S.; Atlanta, Georgia

Silly Books

Where Is Baby's Belly Button? by Karen Katz

Lift the cardboard flaps to find various baby body parts, and then reinforce the lesson with a little tickle.

Doggies by Sandra Boynton

Board-book master Boynton tricks even the most dignified parents into barking 10 different ways (with a meow thrown in for good measure).

Baby Danced the Polka by Karen Beaumont

Boogie down with the book's baby, who also can't resist a cha-cha or a shooby-dooby.

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