At about 4 months, diaper changes with my son, Miles, became quite a challenge. With those little legs moving like he was running a sprint, getting the diaper on and off was quite a feat. But that motion had a purpose. He was building up the leg muscles he needed to crawl, stand, and eventually walk. And the way he seemed as if he couldn't stop himself from moving? In a way, he couldn't -- the part of the brain that would tell him to stop before wearing himself out, the part responsible for impulse control, just doesn't exist yet in an infant. So babies kick and kick, and that's a good thing, because if they had control of their impulses they wouldn't build up the muscles needed to be walking by 15 months.Creeping and Crawling
Muscle development tends to progress from head to toe, with babies gaining head control, then developing arm strength, and lastly building up those leg muscles. Babies often move backward first, because it's easier to push those heavy legs backward than drag them along forward. Once babies learn to crawl, usually around 7 months, their whole world changes and widens. Curiosity motivates crawling, says University of California at Berkeley psychology professor Joseph J. Campos, PhD, a leading researcher in infant mobility. "It gives them a reason to put the muscles together to crawl." Babies become more curious about the world because they can see more of it. That toy on the other side of the room used to be just a blur, but by 8 months vision focuses to nearly perfect 20/30. Space and distance become real concepts. Before your baby can crawl, if you point at something, he will look at your finger. But by 10 months, he'll look instead in the direction you're pointing that finger. He understands that there is a world beyond his line of sight.
This awareness of distance will lead to a habit called "emotional refueling," where the baby will crawl away from Mom, explore something, then crawl back just to "check in." This is a leap in cognitive development, as your baby realizes that he can choose how much distance there will be between the two of you and he tests how far away he can be and feel safe.