first crytical period 0-20 days second crytical period 21-28 days, 3-4wks

As a result of many years of scientific research, it has been determined that the first critical period covers the entire first three weeks of a puppy’s life, 0 to 20 days.

During this period a puppy’s mental capacity is nearly zero and the puppy reacts only to its needs of warmth, food, sleep and it’s mother.

Tests were carried out to determine whether a puppy was capable of learning anything at all during the first critical period, it was determined that it is not.


Scientists found, however, that something nearly miraculous happened on the 21st day and it occurs in all dogs, regardless of breed, on this day all of a puppy’s senses begin to function. The senses were present in the puppy during the first critical period bet were dormant. The 21st day marks the beginning of the second critical period.

During this period the new puppy needs its mother more than at any other time. The brain and nervous system begin to develop. Awareness begins to take place and in the mental state, a puppy’s experience can be rather frightening.

A puppy removed from its mother during this second critical period will never attain the mental and emotional growth that it could. During the second critical period the social stress of being alive has its greatest impact on a puppy. No other time in a dogs life is so crucial to emotional growth.

It is during the second period that the characteristic of nervousness can generate shyness and other negative qualities in a puppy. Once negative characteristics have been allowed to develop ( during second period) no amount of reconditioning or training later in life alter the negative characteristics.