ilities that are very much specialized, such as
musical ability, artistic ability, etc., may exist in high order while
other mental functions may be only mediocre. It is a common thing for a
musical person to be of rather poor ability otherwise. To the extent
that special abilities require specialized differences in the structure
of brain, nervous system, or sense organ, they can exist in some degree
of independence of other functions. Musical ability to some extent does
require some such differences and may therefore be found either with a
high or a low degree of ability in other characteristics.

It is doubtless true that at maturity the unequal power of mental
functions in the same person may be partly due to the fact that one
function has been exercised and others neglected. A person having very
strong musical tendencies is likely to have such a great interest in
music that he will think other activities are not worth while, and will
consequently neglect these other activities. It will therefore turn out
that at maturity the great differences in mental functions in such a
person are in part due to exercise of one function and neglect of
others. But there can be no doubt that in many cases there are large
original, inherited differences, the individual being poor in one aspect
of mind and good in others. Feeble-minded people are usually poor in all
important aspects of mind. However, one sometimes finds a feeble-minded
person having musical or artistic ability, and often such a person has a
good rote memory, sometimes a good verbal memory. However, the so-called
higher mental functions--logical memory, controlled association, and
constructive imagination--are all poor in a feeble-minded person.

Each mental function may be looked upon as in some measure independent;
each is found existing in people in varying degrees from zero ability up
to what might be called genius ability. The frequency curves in Fig. VI
show this. Take rote memory for example. Idiots are found with
practically zero ability in rote memory. At the other extreme, we find
mathematical prodigies who, after watching a long freight train pass and
noting the numbers of the cars, can repeat correctly the number of each
car. Rote memory abilities can be found representing every step between
these two extremes. This principle of distribution holds true in the
case of all mental functions. We find persons practically without them,
and others possessing them