Dog behaviour and pack instict
What does your dog want most in life? Above all, he or she wants to be safe. He wants to know that the group he lives in, which includes himself, you, other members of your human family, and any other pets you have, is not in danger of being harmed or destroyed by any other group or individual.
Your dog is a direct descendant of millions of wild dogs who all felt the same way. Nothing you will do will eradicate this strong feeling, the instinct for survival as part of a group.
Over millions of years, dogs who were members of packs with weak or stupid leaders did not survive to breed. Those who were members of well-led packs often did survive to breed, however, passing on the instinct to the generations that followed, including your dog. You must understand and work with this instinct.
In an orderly pack, the leader is the smartest and often, but not always, the strongest dog. Under him or her is a dog who can boss every dog except the top dog, and so on down through the pack. At the very bottom of the pack is a dog who cannot boss anyone and has to obey every other dog in the pack. Each dog obeys the dogs above him and bosses around those below him on the scale.
Each dog must find his or her place within the pack. This is done by testing the other pack members. /testing can take many forms: a dog can bite or snarl at another dog and try to make him run away or lie down in a belly up position, which says "I give up. I admit you're the boss over me. I believe this so much that I will turn my belly up toward you so you could bite it if you wanted to, because I will do whatever you say from now on".
Or a dog may simply indicate by subtle body language that he believes himself to be superior over the dog he is challenging. He may, for instance, simply stiffen his legs and move "like a table, walking in slow motion toward or around another dog that he wants to intimidate. If the other dog flattens his ears down against his head and lies down exposing his belly, the first dog has won. If the dog being threatened thinks he is higher in rank, he will grab for the neck of the challenging dog and a dog fight will ensue. Whoever wins the fight will be the winner. From then on, the higher dog will be able to intimidate the lower dog merely by walking up to him and assuming a challenging position (such as a stiff-legged walk) or even just by looking sternly at him.
These power games may seem rather pointless when you live not in the wilds surrounded by wolves, lions, or bears but in a house in a city. Yet all dogs, regardless of how tame they are, are motivated by pack instinct. They all want safety in their lives. And the only way they can feel safe is if they know they have a strong, smart leader to their pack. This leader must be you.
Your dog will challenge you to see whether you are smart enough or strong enough to be a safe choice for pack leader. Different dogs will challenge you in different ways. A big strong, rambunctious dog may try to prevent you from doing something he doesn't like (such as putting your hand near his food bowl when he is eating) by growling at you or even biting. A tiny dog can behave in exactly the same way. A dog with a less bold temperament may simply roll over and expose his or her belly when you come near, "asking" you to please be the pack leader and boss him or her around. Your dog could challenge your right to be pack leader by refusing to do what you say, whether it is expressed by not coming when called or not heeling when you are on a walk.
Dogs see things in black and white, yes or no. If your dog does not obey you completely, he does not accept you completely as pack leader. This means that in an emergency he will use his own judgement rather than do what you tell him to. In "civilization" this could have very bad consequences. A dog who decides to use his own judgement instead of following yours may decide to bite the intruder who is breaking into your home - perfectly sound thinking for a dog, but not good thinking for a "pack" living in a city where a friend may come over and your dog bites them. It is safer for the human to make choices not the dog. Therefore, you must be top dog at all times and under all circumstances, and your dog must accept your position without question.