My baby this week: 7 1/2 months

Your baby is beginning to understand a lot about how things in his world work. Some of the concepts may seem basic to you, but they're revelations to an infant. One example is "object permanence," or understanding that an object continues to exist even after it disappears from sight. Earlier, he may have been distressed by your disappearance (even if it was just to hide your face in your hands): He didn't understand where you went. But he now knows that when you cover your face, you're still right there — and he's delighted to discover he was right when you move your hands away and gently say "Boo!" You can play a variation of this game by covering a toy with a blanket or holding it behind your back for a few seconds.

Similarly, if your baby drops a toy or his pacifier out of his crib, he may look over the edge for it — whereas in the past he cried for the object because it had "gone missing." This is one more exciting baby step away from the complete helplessness of an infant and toward the increasing self-reliance of an older baby.

[Babycenter]