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 intel- 
ligence, 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 ac- 
complishments 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 so- 
called mental alertness tests or intelligence scales, aim to 
provide a sampling of performance typical of what the per- 
son examined would do under a wide variety of circum- 
stances. To do this, it is inevitable that tasks be presented 
whose performance calls for certain specific abilities in addi- 
tion to the more universal modes of response which it is the 
real purpose of the test to disclose. One’s score in an intel- 
ligence 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 indi- 
cation of a young man’s capacity to succeed in a professional 
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