By now, you may have already told your baby that the telephone is not a toy, or that rattles are not for throwing, or that his or her sister's hair is not for pulling. Understanding of such abstract ideas will come later. At this age your baby isn't being disobedient or willful – just curious.
The best tactic is to use a simple "no" and then distract him or her.
Figuring out how objects relate
Your baby's beginning to understand how objects relate to one another in three-dimensional space. He or she may stack rings or other toys on top of each other.
If your baby admires his or her reflection in a mirror and you suddenly appear from behind, he or she is now likely to turn and look for you instead of believing that you're in the mirror itself.
A simple game of peekaboo might be absolutely fascinating to your baby. That's because he or she is starting to understand object permanence (that an object that can't be seen can still exist) and loves games in which people or things appear and disappear.