When do babies learn to lie?...

The other night Sweet Baby Grace was playing on the floor. So angelic, I notice something is in her mouth. I say to her Grace, do you have something in your mouth? She stops chewing on it and smiles shaking her head "No" I pick her up to find a piece of carpet that shes been chewing on. I say "Gracie, no,no you cant chew on carpet." her response "ha da" followed with clapping! Who could be mad at that!