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
distribute the repetitions. Suppose you are memorizing "Psalm of Life"
to be recited a month from to-day, and that you require thirty
repetitions of the poem to learn it. Shall you make these thirty
repetitions at one sitting? Or shall you distribute them among several
sittings? In general, it is better to spread the repetitions over a
period of time. The question then arises, what is the most effective
distribution? Various combinations are possible. You might rehearse the
poem once a day during the month, or twice a day for the first fifteen
days, or the last fifteen days, four times every fourth day, _ad
infinitum_. In the face of these possibilities is there anything that
will guide us in distributing the repetitions? We shall get some light
on the question from an examination of the curve of forgetting--a curve
that has been plotted showing the rate at which the mind tends to
forget. Forgetting proceeds according to law, the curve descending
rapidly at first and then more slowly. "The larger proportion of the
material learned is forgotten the first day or so. After that a
constantly decreasing amount is forgotten on each succeeding day for
perhaps a week, when the amount remains practically stationary." This
gives us some indication that the early repetitions should be closer
together than those at the end of the period. So long as you are
forgetting rapidly you will need more repetitions in order to
counterbalance the tendency to forget. You might well make five
repetitions; then rest. In about an hour, five more; within the next
twenty-four hours, five more. By this time you should have the poem
memorized, and all within two days. You would still have fifteen
repetitions of the thirty, and these might be used i