Dogs are pack animals and many of their behaviors expose this truth. When you get a new puppy one of the foremost and the most critical things that you can do is to create authority. You are the "pack leader" and you must act suitably. A new puppy will instinctively spend a huge amount of time trying to figure out where they fit in the hierarchy of their new home. They do this by trying to create their own control. A few breeds have more forceful personalities such as the terriers or Chihuahuas. Other breeds are more naturally docile.