ke, arbitration, etc.
Having finished writing your list, cover it and see how much of it
you can recite without further study, and how long it takes you to
complete the memorizing. Explain the results obtained.

8. Plot the curve of forgetting from the following data, which give
the per cent, of retention of stanzas of a poem at different
intervals after the end of memorizing.

after 1 day 79%
after 2 days 67%
after 6 days 42%
after 14 days 30%
after 30 days 24%

REFERENCES

Ebbinghaus, _On Memory_, 1885, translated by Ruger and Bussenius,
1918. This is the pioneer experimental study of memory, and is still
worth reading, and is not specially hard reading.

James's chapter on Memory, in Vol. I of his _Principles of
Psychology_, 1890, is still one of the best references, and contains
some important remarks on the improvement of memory.

Of the numerous special studies on memory, mention may be made of that
by Arthur I. Gates, _Recitation as a Factor in Memorizing_, 1917,
which, on pp. 65-104, gives a valuable account of the various devices
used by one who is memorizing.

For the psychology of testimony, see G. M. Whipple's article on "The
Obtaining of Information: Psychology of Observation and Report", in
the _Psychological Bulletin_ for 1918, Vol. 15, pp. 217-248,
especially pp. 233-248. See also a popularly written account of the
matter by Muensterberg, in _On the Witness Stand_, 1908, pp. 15-69.

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CHAPTER XV

ASSOCIATION AND MENTAL IMAGERY

SOMETHING ABOUT THINKING AS RELATED TO MEMORY

Memory plays a part, not only in "memory work", and not only in
remembering particular past experiences, but in all sorts of thinking.
Recall furnishes the raw material for thought. A large share of any
one's daily work, whether it be manual or mental, depends on the
recall of previously learned reactions. Most of the time, though we
are not exactly trying to remember facts committed to memory, we are
recalling what we have previously learned, and utilizing the recalled
material for our present purposes. For example, in conversation we
recall words to express our meaning, and we recall the meanings of the
words we hear. In adding a column of figures, we recall the sums of
the numbers. In cooking a meal, we recall the ingredients of the dish
we wish to prepare, and the location of the various materials and
utensils required for our purpose. In planning a trip, we r