"Laughter helps to cement the relationship between a parent and a baby by creating trust. It's one of the ways your infant 'talks' to you before he can speak," says Robert Provine, Ph.D., professor of psychology at the University of Maryland, Baltimore County, and author of Laughter: A Scientific Investigation.It doesn't take much to tickle a little funny bone, especially if you're willing to put all dignity aside and have some fun yourself. Some sure ways to elicit a giggle, or at least a grin:
0 to 3 months
Contrary to what you may have heard, those earliest smiles aren't caused by gas. They happen when an infant's level of arousal fluctuates -- usually as he's drifting off to sleep.
He'll flash you his first true social smile when he's about 6 weeks old, as he learns to recognize -- and respond to -- other grinning faces, so show him yours often.
3 to 6 months
Starting around age 3 or 4 months, almost every baby will laugh in response to being gently tickled, kissed on the tummy, and bounced. The reason: This stimulation gives an immature nervous system a mild -- and pleasant -- jolt. Repeating sounds, or phrases like "I'm gonna get you," can have the same effect.
6 to 9 months
By now, your baby will have developed one of the prerequisites for a sense of humor: the ability to recognize incongruities. He'll laugh when you do "horse lips" or oink like a pig, for instance, not only because he likes the sounds but also because he knows you don't usually behave that way.
Peekaboo and pop-up toys become hilarious at around 7 months because your baby's come to understand that objects are still there even when he can't see them. Kissing him over and over and playing I'm-gonna-get-you are even funnier than they were a few months ago because he's now able to anticipate what's coming.
9 to 12 months
As your baby grows, he'll become more appreciative of your crazy antics, such as pre-tending to suck on his bottle, sticking out your tongue, walking like a penguin, or doing your best Tina Turner imitation -- any silly behavior is fair game for a smile.
Your little merrymaker may also try to make you chuckle -- playing peekaboo or crawling away to lure you into a game of catch-me. If you respond with exaggerated pleasure, he'll love it -- and you'll both enjoy a good laugh.