There are three types of dogs born in every litter. Picture them in a line. There are the alpha dogs in front leading the way, the dogs in the middle who don't really want to lead, but they will if they have to, and the dogs in the back of the line who are very submissive naturally wanting to follow. These submissive dogs don't want to make rules or tell anyone what to do. This is considered the pack order or pack hierarchy.
Alpha Dogs, also called Front of the Line Dogs—Without strong leadership this type of dog can become very pushy and overprotective. They tend to be very smart with a lot of personality. They will refuse to be ruled by anyone who is weaker minded than they are. In extreme cases they can become aggressive with humans or other dogs. Not because they are mean, but because in their minds the pack's survival depends on having a strong leader and they are confident that they have what it takes to be that leader. They are the soldiers ready to step up and rule the home if needed. You need to earn their respect in order to lead them. Size means nothing. The tiniest dogs can rule the extra large dogs and their humans. The power is all in the mind, not the amount or size of muscle on the body.
Middle of the Line Dogs—The dogs in the middle are easiest to train, but are also easily bored. They need to know the humans are capable of leading the pack. Without a stable-minded leader they are prone to testing their limits and can become overexcited and anxious, which is often mistaken for happiness. They do not necessarily want to lead, but they will if they feel it is needed. Because they are not born to lead, a lack of a strong being to guide them can stress them out and cause them to become unbalanced. They may obsess over things and become destructive to the home.
Back of the Line Dogs—This type is very sensitive and cautious. They can easily become timid, nervous, anxious or fearful. They are not born leaders, nor do they want to be leaders. They need to know someone is taking care of things in a confident, consistent manner or it will cause them stress. They do not feel they have what it takes to keep the pack safe. They are easily upset and will often resort to alarm barking. They are prone to submissive urinating issues and may handle things by hiding. In worst cases they can develop fear aggression towards humans and or other animals.
In addition to temperament types, dogs are also born with energy levels that range from game style working dogs that will go and go until they drop, to true couch potatoes that just want to lay around all day. Providing an appropriate amount of exercise for a dog goes a long way in balancing out their temperament.
While dogs have the same basic canine instincts, it is important to recognize their natural temperament and energy level. The type of dog is ingrained within them and it cannot be changed. For example you cannot turn a back of the line dog into an alpha type, but you can guide any dog into being happy, behaved, even-tempered, well-balanced, trustworthy dogs if they are with the right owners who can understand their natural instincts and give them what they need as a canine animal.