Conner talks back to us all the time. We think it is adorable. When I tell him no, he will look right at me a bark a few times, then go back and do what he was doing. My mother laughs at his "talk back". I haven't really tried to get him out of it because I think it is so adorable (and he is 2 1/2 years old and has talked back since he was 12 weeks).
