Babies are born with a well-developed instinct to startle in response to loud noises. As time goes on, this response turns into a love of surprising noises such as squeaking or rattling sounds. And hearing a sound and then seeing what made it helps your baby understand the connection between a sound and its source.

Appropriate for: 2 to 5 months
Skills developed: Auditory, sense of cause and effect
What you'll need: Common household items that make noise when crumpled up, such as waxed paper or paper bags, and a toy that squeaks or makes another noise

Gather a bunch of things you can make noise with, such as a piece of crinkly wrapping paper, a squeeze toy, or some waxed paper. Sit or lie next to your baby and demonstrate each sound, varying the order so it's always surprising. Then put the noisemakers in your baby's hand and help him or her make the sounds.

Repeat this activity over the coming months. It's fun to see when your baby starts to realize he or she is making the sounds.