I have a lab and a chessie as I stated earlier. Labs will always hold a place in my heart. Now having said that I do believe that chessies may be a little too smart for some people to train and that is why (after failure) some call them hard headed. I' m not trying to put anyone down here but he has done so many things that make me think his training through before I act so I can stay one step ahead of him. Mine too is a goof off and is not a bit aggressive to any other dog and once he decides that I am going to insist that he does what he is told he does not forget it. I did have one years ago that was just plain mean but I got him as an adult and think he may have been mistreated before I got him.