There are very distinct stages of a puppy's development. Sometimes your puppy may suddenly become frightened of something they were never bothered by before.
Early Socialization period
6 to 12 weeks
Learns not to bite too hard.
Learns to relate to other litter mates and develops a pack hierarchy through play
This is the age when most rapid learning occurs. Greatest impact on future social behavior will be made by any experience that happens at this point.
Fear Imprint Period
8 to 11 weeks
Anything that frightens the puppy during this period will have a more lasting effect than if it occurred at any other time.
10 to 16 weeks
This period is known as the "period of cutting teeth and apron strings."Pups will attempt to clarify the pack and leadership
Flight Instinct Period
4 to 8 months
He may challenge you in an attempt to resolve the question of leadership.He may not come when called.He may not play fetch even though he once did.
Second Fear Period
- In large breeds this period could extend longer since it is tied to sexual maturity.
- May suddenly be apprehensive about new things or shy or timid of new people or situations.
- Puppy begins to mature sexually: male begins to lift leg, and female that have not been spayed will have first heat period anywhere from 6-12 months.
- Puppy coat being replaced by adult coat, starting down the spine.
If you were lax in your work earlier on you may now see the things you have missed: object guarding, unfavorable reactions towards unfamiliar people, animals, or things that your dog missed during the socialization stage.