function is limited both as to amount and as to the period during which
it must be attained. The physiological limit of improvement has been
thought of as one which was rather easily reached. The loss of
plasticity of the nervous system has been supposed to be rather rapid,
so that marked improvement in a habit after one has passed well into the
twenties was considered improbable. Recent experiments, however, seem to
show that no such condition of affairs exists. There is very great
probability that any function whatsoever is improvable with practice,
and in most cases to a very marked degree. To find a function which has
reached the physiological limit has been very rare, even in experimental
research, and even with extended practice series it has been unusual to
reach a stage of zero improvement even with adults. Thorndike says, "Let
the reader consider that if he should now spend seven hours, well
distributed, in mental multiplication with three place numbers, he would
thereby much more than double his speed and also reduce his errors; or
that, by forty hours of practice, he could come to typewrite (supposing
him to now have had zero practice) approximately as fast as he can write
by hand; or that, starting from zero knowledge, he could learn to copy
English into German script at a rate of fifty letters per minute, in
three hours or a little more."[3] It is probably true that the majority
of adults are much below their limit of efficiency in most of the habits
required by their profession, and that in school habits the same thing
is true of children. Spurious levels of accomplishment have been held up
as worthy goals, and efficiency accepted as ultimate which was only two
thirds, and often less than that, of what was possible. Of course it may
not be worth the time and energy necessary to obtain improvement in
certain lines,--that must be determined by the particular case,--but the
point is, that improvement; is possible with both children and adults in
almost every habit they possess with comparatively little practice.
Neither the physiological limit of a function nor the age limit of the