nd observing, but doing
and observing _are_ learning.

Retention

We come now to the second of our four main problems, and ask how we
retain, or carry around inside of us, what we have learned. The answer
is, not by any process or activity. Retention is a resting state, in
which a learned reaction remains until the stimulus arrives that can
arouse it again. We carry around with us, not the reaction, but the
machinery for making the reaction.

Consider, for example, the retention of motor skill. A boy who has
learned to turn a handspring does not have to keep doing it all the
time in order to retain it. He may keep himself in better form by
reviewing the performance occasionally, but he retains the skill even
while eating and sleeping. The same can be said of the retention of
the multiplication table, or of a poem, or of knowledge of any kind.
The machinery that is retained consists very largely in brain
connections. Connections formed in the process of {349} learning
remain behind in a resting condition till again aroused to activity by
some appropriate stimulus.

But the machinery developed in the process of learning is subject to
the wasting effects of time. It is subject to the law of "atrophy
through disuse". Just as a muscle, brought by exercise into the pink
of condition, and then left long inactive, grows weak and small, so it
is with the brain connections formed in learning. With prolongation of
the condition of rest, the machinery is less and less able to
function, till finally all retention of a once-learned reaction may be
lost.

But _is_ anything once learned ever completely forgotten and lost?
Some say no, being strongly impressed by cases of recovery of memories
that were thought to be altogether gone. Childhood experiences that
were supposed to be completely forgotten, and that could not at first
be recalled at all, have sometimes been recovered after a long and
devious search. Sometimes a hypnotized person remembers facts that he
could not get at in the waking state. Persons in a fever have been
known to speak a language heard in childhood, but so long disused as
to be completely inaccessible in the normal state. Such facts have
been generalized into the extravagant statement that nothing once
known is ever forgotten. For it is an extravagant statement. It would
mean that all the lessons you had ever learned could still be recited,
if only the right stimulus could be found to arouse them; it wou