ANALYSIS OF THE WORKER
One of the alleged common factors is the ability to learn,
the ability to profit by experience, the ability to modify
behavior in order to achieve a purpose, the ability to shape
one’s acts in the light of an end to be sought. This ability
is usually called intelligence. No one questions that intelligence,
 as so defined, is the outstanding characteristic of the
animals higher in the evolutionary scale; or that it is most
indispensable in those human beings whose professional accomplishments
 are superlative. The controversy is as to
whether this all-important ability called intelligence is a
general common factor conditioning in greater or smaller
degree all of a person’s acts of adjustment, or whether it is
simply a convenient abstract term used to refer to a sum
total of many specific abilities, similar in some regards but
independent of each other.
The literature on this topic is of appalling extent, and
includes much statistical as well as theoretical material. The
issue has been beclouded somewhat by the tendency to
identify the alleged common factor, intelligence, with the
ability measured by some well-known test such as Army
Alpha or the Binet-Simon series. These tests, like all socalled
 mental alertness tests or intelligence scales, aim to
provide a sampling of performance typical of what the person
 examined would do under a wide variety of circumstances.
 To do this, it is inevitable that tasks be presented
whose performance calls for certain specific abilities in addition
 to the more universal modes of response which it is the
real purpose of the test to disclose. One’s score in an intelligence
 test is then first of all a measure of specific ability,
of ability to do precisely the things required of him in that
test. So far as these responses are identical, wholly or in
part, with elements of responses needed in other situations,
the test becomes a partial measure of ability to meet these
other situations also. Even such a limited sampling of
verbal problems as Army Alpha gives something of an indication
 of a young man’s capacity to succeed in a professional

60