Doctor my son is 2 years old and he is not talking a single word.he some time respond when we call him not all the time but if we hold him and sing rhymes he looks into our eyes.he does things like when we saying Johny johny yes papa open ur mouth he laughs saying hahaha. If we say happy birthday song he claps. First he used to point out to people on the photo and used to do many things but suddenly he got engrossed in the phone so much.most of the time he wants phone.is there anything to worry