dear son is still doing that!!! but much more better than before. we will tell him firmly "NO!" then he will take the things/toys out from his mouth. sometimes he will purposely put something into his mouth and look at us just to see how we react. and sometimes he will act as if he is chewing something and come to us to show us he is 'eating' something, but when we check his mouth, NTH was inside. LOL!