_Prolonged Infancy and the Long Period of Plasticity in the Infant Make
Training and Education Possible_

The child is born the weakest and most helpless of creatures. Unlike the
young of most animals, which within a few hours after birth move about and
perform most of the movements necessary to their existence, the infant is
so helpless that all its needs must be supplied by parents, otherwise it
would perish. Immediately after birth a colt or calf can walk or run almost
as fast as its mother; the chick just out of its shell can run about and
peck at its food. The child at one year of age can barely totter around and
all of its needs must be looked after by others. Moreover, the infant at
birth is practically blind and deaf and the senses of taste and smell and
touch just sufficiently developed to enable it to take nourishment.

This slowness of development, or prolonged infancy as it is called, is of
vast significance to the child. It marks at once the chief distinction
between the human infant and the young of all other animals. It makes
possible a long period of adjustment and training which otherwise would be
impossible. Most animals are born with a nervous system highly developed
and with most of the adjustment to the environment ready made, so that
after a short time all the activities of life are perfected and thereafter
automatic action and instinct rule their lives. Because of this lack of
infancy and absence of plasticity of the nervous system, animals are little
more than machines that perform their task with unvarying regularity in
response to outside stimulations. Animals, therefore, are unable to adjust
themselves to a change in environment, and as a result their lives are in
constant danger. In fact, countless millions of the lower forms of life are
perishing every hour because of the lack of possibility of adjustment.