* Dominance. Dogs as pack animals will often seek to dominate others in their pack or family (acquire more status and authority) if they feel they are able. A dog that seeks to dominate may use aggression as a means to elevate its perceived power and authority, or to make others respect its wishes and not challenge it. Pet owners are generally encouraged to not allow a dog to become overly dominant due to the aggressive behavior that may result. Dominance may include "pushy" behavior, refusal to show respect or obedience to humans, attempted "ownership" of high status locations such as beds, sofas, or doorways, and in general, any type of behavior the animal sees as furthering a dominant social role.
* Fear and self-defense. Like humans, dogs react when fearful, and may feel driven to attack out of self defense, even when not in fact being "attacked". Speed of movement, noises, objects or specific gestures such as raising an arm or standing up may elicit a reaction. Many rescued dogs have been abused, and in some dogs, specific fears of men, women, skin coloring, and other features that recall past abusers, are not uncommon. A dog that feels cornered or without recourse may attack the human who is threatening or attacking it. A dog may also perceive a hand reached out toward its head as an attempt to gain control of the dog's neck via the collar, which if done to a wary dog by a stranger can easily provoke a bite.
* Territoriality and possessions. See above. Aggressive possessiveness is considered a very important type of aggression to test for, since it is most associated with bites, especially bites to children.
* Predatory instincts. In isolation, predatory behaviors are rarely the cause of an attack on a human, although with large dogs or very small children this may sometimes occur. Predatory aggression is more commonly involved as a contributing factor for example in attacks by multiple dogs; a "pack kill instinct" may arise if multiple dogs are involved in an attack.
* Pain or sickness. See above. As with fear, pain can incite a dog to attack. The canonical example of sickness-induced attack is the virulent behavior caused by rabies.
* Redirected aggression. A dog that is already excited/aroused by an aggressive instinct from one source, uses an available target to release its aggression. From Wikipedia, the free encyclopedia.
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