minantly social or mechanical in character. Some of the
tests are fairly adequate for mechanical intelligence, but no good
tests have been devised for social intelligence. These tests,
however, as used in the army and for appraising college entrants,
as at Columbia University, have been demonstrated to be fairly
good indices of general intelligence.]

Individual differences are, therefore, seen to be not simply
differences with respect to given mental traits, but differences
with respect to general mental capacity. Experimental
investigation points to a graded difference in mental capacity,
ranging from idiocy to genius, the largest group being normal
or average, the size of the group diminishing with further
deviation from the average in either direction.

Certain important correlations, furthermore, have been
found between the level of intelligence and the level of character.
The great in mind, it may be said briefly, are also great
in spirit. "General moral defect commonly involves intellectual
inferiority. Woods and Pearson find the correlation between
intellect and character to be about .5.... General
moral defect is due in part to a generally inferior nervous
organization."[1]

[Footnote 1: Thorndike: _Educational Psychology_ (1910), p. 224.]

One other important correlation must be noted. While
gifts and capacities are specific, superiority in a given trait
commonly involves superiority in most others. Exceptional
talent in one direction in most cases involves exceptionality
in many other respects. While talents are not indiscriminately
transferable from one field to another, the same complex
of traits which makes a person stand out preeminently in
a given field, say law, would make him stand out in any one of
half a dozen different fields into which he might have gone.
There seems to be no evidence that extraordinary capacity in
one direction is balanced by extraordinary incapacity and
stupidity in others. The fact that individuals differ not only
in specific traits but in general mental capacity has, also,
certain obvious practical consequences. It means that there are
present in society, in the light of recent tests in the army, an
unexpectedly large number of individuals below the level of
normal intelligence. One in five hundred, Thorndike estimates,
is the "frequency of intellectual ability so defective as
to disturb the home, resist school influence, and excite popular
derision." These are clearly