During the first three critical periods, insignificant brainwaves from a puppy can be recorded on electroencephalographs. The fourth critical period, however, is quite different. The first actual – and highly significant – waves can be recorded.

It is during this fourth period that a bond will be established between dog and man that will have a lasting effect upon the puppy. During no other phase in its life will a canine have the ability to achieve a stronger bond than during the fourth critical period.

A puppy’s contact with people during this phase is the whole key to his emotional and social success within human society. In the tests conducted at Bar Harbour, puppies were isolated at various intervals during the five critical periods and it was determined that isolation from human society had its greatest effect on puppies during the fourth critical period. Without adequate human contact during the fourth period puppies became incapable of being trained and incapable of being companions to man.

It is during this time that a puppy should be integrated into human society. At this time a puppy should be taken for walks, meet people and be allowed to play with children and other animals (under supervision)

During the fourth period simple commands can – and should – be taught. There should be gentle discipline. Forceful discipline during this period could adversely tip the scales on which the puppy’s emotional development now rests. A puppy (during the fourth critical period) is learning to live in a human’s world. He is learning to trust and have confidence in human beings.

A puppy between the ages of 8 and 12 weeks does not deliberately get into mischief. A physical and forceful correction could result in complete confusion within the mind of the puppy. Faith and trust in his new human friends could be quickly shattered. When mistrust of humans develops during the fourth critical period, that mistrust will remain a permanent part of a puppy’s make up.

Because many people acquire puppies for home security purposes, I must digress for just a moment to put across a very important point. The preceding paragraph may cause some to assume that the best way to raise a puppy to be a watchdog is to isolate it from human society during its fourth critical period - so it will distrust humans. This is not the way to train a watchdog. It is one way to guarantee that he will never be protective of anything.

During the fourth critical period discipline should be confined to scolding. Scolding does not include shouting. Commands such as “sit” “stay” and “come” can be taught during the fourth critical period – but must be done so in a playful atmosphere.
Housebreaking should be instituted in a gentle manner, insuring that praise is used for correct behaviour rather than forceful correction for misbehaviour.