Another important condition of impression is repetition. It is well
known that material which is repeated several times is remembered more
easily than that impressed but once. If two repetitions induce a given
liability to recall, four or eight will secure still greater liability
of recall. Your knowledge of brain action makes this rule intelligible,
because you know the pathway is deepened every time the nervous current
passes over it.

Experiments in the psychological laboratory have shown that it is best
in making impressions to make more than enough impressions to insure
recall. "If material is to be retained for any length of time, a simple
mastery of it for immediate recall is not sufficient. It should be
learned far beyond the point of immediate reproduction if time and
energy are to be saved." This principle of learning points out the fact
that there are two kinds of memory--immediate and deferred. The first
kind involves recall immediately after impression is made; the second
involves recall at some later time. It is a well-known fact that things
learned a long time before they are to be recalled fade away. If you
are not going to recall material until a long time after the
impression, store up enough impressions so that you can afford to lose
a few and still retain enough until time for recall. Another reason for
"overlearning" is that when the time comes for recall you are likely to
be disturbed. If it is a time of public performance, you may be
embarrassed; or you may be hurried or under distractions. Accordingly
you should have the material exceedingly well memorized so that these
distractions will not prove detrimental.

The mere statement made above, that repetition is necessary in
impression, is not sufficient. It is important to know how to