Because humans and dogs have different communication systems, misunderstandings may occur between the two species. A person may intend to be friendly toward a dog, or at least not threatening, but the dog may perceive the person's behavior as threatening or intimidating. Dogs show aggression for many different reasons and often for more than one reason. Dominance aggression is motivated by a challenge to a dog's social status or to its control of a social interaction. Dogs are social animals and normally live in groups or packs.
Dogs view their human families as their social group.
If a dog perceives its own ranking in the hierarchy to be higher than that of its owners, it is likely the dog will challenge the owner in certain situations. Because people do not always understand canine communication, they may challenge the dog's social position inadvertently, without even being aware they are doing so. Dominantly aggressive dogs may growl when disturbed when resting or sleeping, especially from a favorite spot such as the couch or the bed. Physical restraint, even when done in a friendly manner like hugging may also cause the dog to respond aggressively. Reaching for the dog's collar or reaching out over its head to pet it can be interpreted by the dog to be dominance challenges.