is as if it had a
number of special keys opening special locks. The power of
modifying these instinctive adjustments, the capacity of
learning, is like being put in possession of a pass-key. As
Professor Dewey puts it, "An original specialized power of
adjustment secures immediate efficiency, but, like a railway
ticket, it is good for one route only. A being who, in order to
use his eyes, ears, hands, and legs, has to experiment in making
varied combinations of their reactions, achieves a control
that is flexible and varied."[1]

[Footnote 1: Dewey; _Democracy and Education_, p. 53.]

The more complex the environment is in which the individual
must live, the longer is the period of infancy needed in
which the necessary habits and capacities may be acquired.
In the human being the period of infancy extends in a literal
sense through the first five years of the individual's life. But
in civilized societies it extends factually much longer. By the
end of the first five years the child's physical infancy is over.
It can take care of itself so far as actually feeding itself, moving
about, and communicating with others is concerned. But
so complex are the habits to which it must become accustomed
in our civilization that it is dependent for a much
longer period. The whole duration of the child's education is
a prolongation of the period of infancy. In most civilized
countries, until at least the age of twelve, the child is literally
dependent on its parents. And with every advance in civilization
has come a lengthening in the period of education, or
learning.

Intellectually, the period of infancy might be said not
really to be over before the age of twenty-five, by which time
habits of mind have become fairly well fixed. The brain and
the nervous system remain fairly plastic up to that time, and
if inquiry and learning have themselves become habitual,
plasticity may last even longer. In the cases of the greatest
intellects, of a Darwin, or a Newton, one might almost say
the period of infancy lasts to old age. To be still learning at
sixty is to be still a child in the best sense of the word. It is
still to be open rather than rigid, still to be profiting by
experience.

The great social advantages of the prolonged period of
infancy lie in the fact that there is a unique opportunity both
for the acquisition by individuals and for the imposition on
the part of society of a large number of habits of great social
value