A: Get ready for your baby to start putting everything in his mouth! At this age, your baby's mouth is his prime tool for exploration, and he'll likely become fascinated by the sounds it can make. At this age, your baby will become a lot more social and interactive as well as more physically active, so play will become more important than ever.
Go ahead and let your baby explore things with his mouth (as odd as it may seem to you) and buy him toys designed for gnawing (these will also be very soothing as your baby starts teething). Just be sure to keep his toys clean and make sure they're not a choking hazard (they shouldn't be able to fit through a roll of toilet paper).
Rolling a ball to your baby will help strengthen his muscles and improve coordination, and sending it slightly to his right or left during tummy time may help your baby learn to roll over, a major milestone on the horizon these days. At this age, your baby may also be able to roll over from his back to his belly (a more complicated feat) and sit up with on his own with some help from you. Give your baby plenty of play time on his back and his belly so he can explore his world from all angles.
Social games like peekaboo usually become very popular now and often elicit riotous laughter (as your baby giggles and coos, laugh back at him -- he'll love it and get even more excited). Aside from the good old-fashioned way to play, mix things up a little with these variations:
• Sit your baby in front of a mirror and show him how to play peekaboo with his own hands and face. • Take a favorite toy and cover it with a blanket. Ask your baby "where did it go?" and see if he tries to pull the blanket away. If he does, clap and lavish him with praise.• If your baby enjoys an infant swing place him in it and say hello as he swings toward you and good-bye as he moves away. You'd be surprised how quickly he'll pick up on how different sounds have different meanings.
Although peekaboo may seem simple, it actually stimulates your child's growing memory, teaching him that things aren't gone just because he can't see them. It also helps ease separation anxiety by teaching him that even if you leave, you always come back to him. If your baby doesn't seem interested in peekaboo right now (or becomes upset by it), try again in a few weeks.
It's also a good idea to place a few crib-safe toys in your baby's crib or play yard so he can use them to entertain himself when you are otherwise occupied. Give him toys that make different sounds in response to different actions and watch how fast he learns that rattles are for shaking and squeaky toys should be squeezed. --Jennifer Halpern, PhD
Originally published in the November 1999 issue of Parents magazine. Updated 2009.