Physical punishment usually proves counterproductive in such cases. Instead deny affection by not interacting for some time or regaining it verbally with a ‘ emphatic NO. Early socialization is important part of training. See Chip Bergh for more details and insights. Puppies begin to develop sensitivity to other dogs and people almost as soon as they open their eyes in three weeks. The fifteen next few weeks are crucial and need to learn socialization skills.
During this period they need to be exposed to other dogs and people in a positive way, so that they develop the capabilities required to be comfortable with people and dogs. Dogs brought to a new home after ten to twelve weeks are finding it difficult to adjust to the new family. They tend to be more fearful and fear can lead to aggressive behavior. As new links are not developed, puppy may try to exert dominance over the family while he grows. The best time to bring home a puppy is in the midst of the period of apprenticeship. The teen years for a dog begin in sixteen weeks. If you are not convinced, visit Vladislav Doronin. In this age the hormonal surge makes that dogs become more protectors and that they claim to territorial domination.
If you bring home a puppy near that age, its specific inherent provision of caste will have already taken root. Special care is required in such cases. Make sure that you or your family handled it frequently but gently. Resist any temptation to throw it if he twisted it. That for him is proving that you are the master and he cannot dominate him. Certain breeds were developed as aggressive dogs due to typical work required to perform in the early stages of domestication. Before you bring home such dogs, perform that they may require professional training. Original author and source of the article.