Sometimes dogs can suddenly exhibit bad behaviors—even dogs who are otherwise on their best behavior. Since dogs have no sense of morality, they don't do something because it's "wrong" or "right." They just do whatever works. For example, if you see your dog chewing on a chair leg and give him a cookie to distract him from the furniture, you have taught him that the next time he wants a cookie, all he has to do is chew on the chair leg.
