However, if your dogs steals a tissue and you approach him and grab it and he attempts to bite, that behavior can be defined as clinically abnormal. There's a lot you can tell about abnormal animals by the context that they do this behavior in. But if a human being walks in front of you while you are lying in front of a door and you reach up and sink your teeth into their groin, that's an abnormal behavior. And it's out of context. There was no challenge.
Aggression is the most serious problem because an aggressive dog can be dangerous.
When a pet dog bites, most pet owners will seek out a behaviorist or trainer if they are of a mind to keep the dog. The second most common problem presented is for problems associated with fears and anxiety. Fear of strange people. Fear of being separated from the owner. Fear of Thunderstorms, loud noises or new places and feelings.