Dogs: Learned Behavior vs. Natural Instincts
All dogs have natural instincts that never have to be taught. Some breeds exhibit specific instincts such as chasing small animals, tracking smells or staying near their owner when walking. These traits are generally found in the majority of all dogs of a specific breed. Some do have issues knowing what breed they really are, such as a large dog sometimes fits in better with his smaller breed house mates.
Natural instincts are the behaviors that are hard wired into a dogs brain. Many dogs may need guidance when first using their instincts but catch on a lot quicker then other breeds. Hundreds of years ago dogs had specific duties, few were kept as just pets. Hounds were for hunting and tracking, bulldogs were for child care, herd dogs were for herding livestock, shih tzu's were for warmth. Each had a job and natural knew what it's job was.
Many dogs can be taught to do any type of job from medical service to skate boarding. Learned behaviors are those that are taught to the dog. Any breed can be a service dog depending on the type of service the dog must perform. Instincts do play a part in the training process. Search dogs are generally dogs that have the natural instinct to track or hunt such as many breeds of hounds. However, German shepherds have a great success rate in search type jobs.
Dogs learn to follow commands through training much like a toddler learns to use the restroom. The commands a dog learns to follow and the job it is taught to do easily becomes second nature to the dog. However, instincts may occasionally take over and cause some unpredictable outcomes.
Learned Behavior or Natural Instinct in Fighting
Dogs have a natural instinct to defend themselves. Some dogs are Alphas while others are Betas. The Alphas will assert dominance over the Betas or will attempt to do so over another Alpha, that is a natural instinct. Dogs that are well socialized and trained will introduce themselves to other dogs and typically don't try to dominate because they were taught not to.
In dog fighting though, dogs are forced to fight each other. When dogs generally fight they are trying to determine who is in control. Dogs that are fought illegally, are taught not to stop fighting when the other dog is down. Instincts however, tell a dog that once their opponent is down or submits the fight is then over. Fighting dogs are often punished for submitting and for stopping once the other dog submits.
Dogs that are used for fighting aren't granted the option to follow their instincts, they have learned behaviors that control their actions. When their instincts tell them to stop fighting, their owners beat them. Taught behavior causes this dogs to kill other animals. It is literally kill or be killed which natural instincts tell them to survive at all cost, even if that means obeying their owners.