it varies tremendously with the individual. Third, rhythm is
always an aid when it can be used, such as learning the number of days
in each month in rhyme. Fourth, after a period of hard mental work a few
minutes (Pillsbury thinks three to six) should elapse before definitely
taking up a new line of work. This allows for the so-called "setting" of
associations, due to the action of the general law of inertia, and tends
to diminish the possibility of interference from the bonds called into
play by the new work. Fifth, mnemonic devices of simple type are
sometimes an aid. Most of these devices are of questionable value, as
they themselves require more memory work than the facts they are
supposed to be fixing. However, if devised by the learner, or if
suggested by some one else after failure on the part of the learner to
fix the material, they are permissible.

Memory has been classified in various ways, according to the time
element, as immediate and permanent. Immediate memory is the one which
holds for a short time, whereas permanent memory holds for a long time.
People differ markedly in this respect. Some can if tested after the
study period reproduce the material with a high degree of accuracy, but
lose most of it in a comparatively short time. Others, if tested in the
same way, reproduce less immediately, but hold what they have over a
long period. Children as a whole differ from adults in having poorer
immediate memories, but in holding what is fixed through years. Of
course permanent memory is the more valuable of the two types for most
of life, but on the other hand immediate memory has its own special
value. Lawyers, physicians, politicians, ministers, lecturers, all need
great power of immediate memory in their particular professions. They
need to be able to hold a large amount of material for a short time, but
then they may forget a great deal of it.

Memory is also classified according to the arrangement of the material
as desultory, rote, and logical memory. In desultory memory the facts
just "stick" because of the great retentive power of the brain, there
are few connections, the material is disconnected and disjointed. Rote
memory depends on a special memory for words, aided by serial
connections and often rhythm. Logical is primarily a memory for meanings
and depends upon arrangement and system for its power. Little children
as a class have good desultory memories and poor logical memories. Rote
memory i