0 - 2 weeks = Neonatal Most influenced by their mother. Touch and taste present at birth.

2 - 4 weeks = Transitional  Most influenced by their mother and littermates. Eyes open, teeth erupt, hearing and smell developing. Beginning to stand, walk a little, wag, bark. By four or five weeks, sight is well-developed.

3 - 12 weeks = Socialization During this period, puppies need opportunities to meet other dogs and people. By four to six weeks they're most influenced by their littermates and are learning about being a dog.

From four to 12 weeks they're most influenced by their littermates and people. They're also learning to play, including social skills, inhibited bite, social structure/ranking and physical coordination.

By three to five weeks they're becoming aware of their surroundings, companions (dogs and people) and relationships, including play. By five to seven weeks they're developing curiosity and exploring new experiences. They need positive people experiences during this time.

By seven to nine weeks they're refining they're physical skills/coordination (including housetraining) and full use of senses.

By eight to ten weeks they experience real fear -- when puppies can be alarmed by normal objects and experiences and need positive training.

By nine to 12 weeks they're refining reactions, social skills (appropriate interactions) with littermates and are exploring the environment, spaces and objects. Beginning to focus on people. This is a good time to begin training.

3 - 6 months = Ranking  Most influenced by littermates (playmates now include those of other species).Beginning to see and use ranking (dominant and submissive) within the pack, including humans. Teething (and associated chewing).At four months they experience another fear stage.

6 - 18 months = Adolescence Most influenced by human and dog  members.

***At seven to nine months they go through a second chewing phase -- part of exploring territory. Heightened exploration of dominance, including challenging humans. If not spayed or neutered, beginnings of sexual behavior