The Wechsler Tests

Binet’s test depended on an age scale; that is, the questions which were answered
correctly by a majority of ten-year-old children were assigned to the
ten-year age level of intelligence. A more sophisticated version of the test devised
by Robert Yerkes depended on a point scale for scoring; this format
was fully developed by David Wechsler. While the Binet-Terman method
used different tests for different age groups, Wechsler worked toward a test
to measure the same aspect of behavior at every age level. The goal of his test
was to measure intelligence in a holistic (encompassing the larger whole of
personality) fashion that did not depend on the verbal skills that the Stanford-
Binet tests required.Wechsler thought of intelligence as a multifaceted
complex of skills, the total of an effective intellectual process; he wanted his
test to show the way intelligent people behaved as a consequence of an
awareness of the results of their actions. He thought that those actions
would be more rational, worthwhile (in terms of social values), and meaningful
than those of less intelligent people.

Wechsler’s first test (the Wechsler-Bellevue Intelligence Scale) was published
in 1939, and it awarded points for each answer depending on the
level of sophistication of the response. The test consisted of six verbal subjects
(information, comprehension, arithmetic, similarities, vocabulary, and
digit span) and five performance subtests (picture completion, picture arrangement,
block design, object assemblies, and digit symbols). The division
into verbal and performance skills permitted the calculation of three
intelligent quotients: a verbal IQ based on the sum of the verbal tests, correlated
with norms of age, a performance IQ based on the sum of performance
tests, and a full-scale IQ derived from the sum of all the answers. The
test was standardized on a sample of adults, and it could be used to test individuals
who had linguistic or sensorimotor handicaps. The pattern of scores
on the separate tests could also be used to diagnose learning disability or, in
some situations, clinical disorder or dysfunction.

The original test was limited by the sample used for standardization, but
the 1955Wechsler Adult Intelligence Scale (WAIS) provided a basis for testing
adults from the ages of sixteen to seventy-five. Further revision in the
standard scale (including the WAIS-R, 1981) updated the test to coincide
with changes in cultural experience. In addition, a Wechsler Intelligence
Scale for Children (WISC) was designed to cover ages five to fifteen in 1949
and was revised (WISC-R) in 1974 to cover ages six to sixteen. In 1991, another
revision (WISC-III) was introduced. Subsequent modifications also
led to a test suitable for preschool children, theWechsler Preschool and Primary
Scales of Intelligence (WPPSI) of 1967, which covered ages four to six
and a half and included mazes, animal figures, and geometric designs. This
test was revised in 1981 (WPPSI-R) to extend its range over three years to
seven years, three months. Further adjustments have also been made to account
for a candidate’s sociocultural background in a test called the System
of Multicultural Pluralistic Assessment (SOMPA, 1977).

Recent definitions of intelligence have resulted in further development
of testing instruments. Raymond Cattell’s proposal that intelligence could
be divided into two types—fluid (or forming) and crystallized (fixed)—led
to a test that used figure classification, figure analysis, and letter and number
series to assess the essential nonverbal, relatively culture-free aspects of
fluid intelligence; it used vocabulary definition, abstract word analogies,
and general information to determine the skills that depend on exposure to
cultural processes inherent in crystallized intelligence. Other theories, such
as Jean Piaget’s idea that intelligence is a form of individual adaptation and
accommodation to an environment, led to the development of a test which
measures mental organization at successive ages.