THE DEVELOPMENT
OF APTITUDE TESTS
Aptitude tests measure more specific and delimited
abilities than intelligence tests. Traditionally, intelligence
tests assess a more global construct such as
general intelligence, although there are exceptions
to this trend that will be discussed later. By contrast,
a single aptitude test will measure just one
ability domain, and a multiple aptitude test battery
will provide scores in several distinctive ability
areas.
The development of aptitude tests lagged behind
that of intelligence tests for two reasons, one
statistical, the other social. The statistical problem
was that a new technique, factor analysis, was
often needed to discern which aptitudes were primary
and therefore distinct from each other. Research
on this question had been started quite early
by Spearman (1904) but was not refined until the
1930s (Spearman, 1927; Kelley, 1928; Thurstone,
1938). This new family of techniques, factor
analysis, allowed Thurstone to conclude that there
were specific factors of primary mental ability
such as verbal comprehension, word fluency, number
facility, spatial ability, associative memory,
perceptual speed, and general reasoning (Thurstone,
1938; Thurstone & Thurstone, 1941). More
will be said about this in the later chapters on intelligence
and ability testing. The important point
here is that Thurstone and his followers thought
that global measures of intelligence did not, so to
speak, “cut nature at its joints.” As a result, it was
felt that such measures as the Stanford-Binet were
not as useful as multiple aptitude test batteries in
determining a person’s intellectual strengths and
weaknesses.
The second reason for the slow growth of aptitude
batteries was the absence of a practical application
for such refined instruments. It was not until
WWII that a pressing need arose to select candidates
who were highly qualified for very difficult
and specialized tasks. The job requirements of
pilots, flight engineers, and navigators were very
specific and demanding. A general estimate of intellectual
ability, such as provided by the group
intelligence tests used in WWI, was not sufficient
to choose good candidates for flight school. The
armed forces solved this problem by developing a
specialized aptitude battery of 20 tests that was
administered to men who passed preliminary
screening tests. These measures proved invaluable
in selecting pilots, navigators, and bombadiers, as
reflected in the much lower washout rates of men
selected by test battery instead of the old methods
(Goslin, 1963). Such tests are still used widely in
the armed services