for example, such as curiosity, flexibility of
native and acquired reactions, sociability, sympathy, and the
like. In a sense an individual possesses not a single intelligence,
but many, as many as there are types of activity in
which he engages. But one may classify intelligence under
three heads, as does Thorndike:[1] mechanical intelligence,
involved in dealing with things; social intelligence, involved in
dealing with other persons; and abstract intelligence, involved
in dealing with the relations between ideas. Each of
these types of intelligence involves the presence in a high degree
of a group of different traits. Thus, in social intelligence,
a high degree of sympathy, sensitivity to praise and blame,
leadership, and the like, are more requisite than they are for
intelligent behavior in the realm of mechanical operations or
of mathematical theory. A person may be highly intelligent
in one of these three spheres and mentally helpless in the
others. Thus, a brilliant philosopher may be nonplused by a
stalled motor; a successful executive may be a babe in the
realm of abstract ideas. But what we rate as a person's general
intelligence is a kind of average struck between his various
competences, an estimate of his general ability to control
himself in the miscellaneous variety of situations of which
his experience consists.

[Footnote 1: "Measuring Intelligence," _Harper's Magazine_, March, 1920.]

There have been a number of tests devised for the purpose
of estimating an individual's general intelligence.[1] On a
rating scale such as is used in these examinations most
individuals will come up to a certain standard that may be
called average or normal. There will be a certain number so
far below the normal rating in a complex of traits that go to
produce intelligent (competent and facile) behavior that they
will have to be classed as subnormal, ranging from
feeblemindedness to idiocy. A certain number will be found so
extraordinarily gifted in general traits and in specific
abilities--in given subject-matters, as, for example, in
mathematics and music--that they will be marked out as geniuses.
Following the laws of probability, the greater the inferiority
or superiority, the more exceptional it will be.

[Footnote 1: These, in large part, deal with words and ideas and
are, therefore, weighted in favor of abstract intelligence, and
put at a discount individuals whose experience and whose intelligence
are predo