About the only thing cuter than a smiling baby is a laughing one -- as you'll soon see (and hear!) for yourself. But how soon, exactly, is hard to say. "Some babies crack up as early as five weeks, and others don't do it until five months," says Ann Douglas, author of The Mother of All Baby Books.

One thing's for sure: Eventually, something's gonna tickle that little funny bone. Douglas's oldest daughter first laughed when Douglas emerged from the shower with a towel wrapped around her head. "It was like, 'Silly Mommy, that's not what you use towels for!'" she says. (Laughing at a "crazy" scene shows healthy cognitive development, too, because it means your child has ideas about the way things ought to be.)

Other things that trip the funny-o-meter for the diapers-and-burp-cloth set: games like peekaboo that provide anticipation and a pleasant surprise; a bit of gentle physical play, like tossing her a few inches in the air (for older babies); and, lastly, good ol' slapstick.

Your child's laugh may be high-pitched and choppy, as if he's channeling Flipper the Dolphin, due to his baby-soft, floppy larynx. Grab a video camera and enjoy: By around a year of age, his larynx will tone up, and he'll simply sound like a little kid with a big sense of humor.

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