Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV)
The predecessors of the WAIS-IV, from the most recent on back, were the WAIS-III, the WAIS-R, the WAIS, the W-B II (Wechsler-Bellevue II),and the W-B I (Wechsler-Bellevue I).
The test’s heritage : In the early 1930s, Wechsler’s employer, Bellevue Hospital in Manhattan, needed an instrument for evaluating the intellectual capacity of its multilingual, multinational, and multicultural clients. Dissatisfied with existing intelligence tests, Wechsler began to experiment. The eventual result was a test of his own,the
W-B I, published in 1939. This new test borrowed from existing tests in format though not in content.
Unlike the most popular individually administered intelligence test of the time, the Stanford-Binet, the W-B I was a point scale, not an age scale. The items were classified by subtests rather than by age. The test was organized into six verbal subtests and five performance subtests, and all the items in each test were arranged in order of increasing difficulty. An equivalent alternate form of the test, the W-B II, was created in 1942 but was never thoroughly standardized (Rapaport et al., 1968).
Research comparing the W-B to other intelligence tests of the day suggested that the W-B measured something comparable to what other intelligence tests measured. Still, the test suffered from some problems:
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Unlike the most popular individually administered intelligence test of the time, the Stanford-Binet, the W-B I was a point scale, not an age scale. The items were classified by subtests rather than by age. The test was organized into six verbal subtests and five performance subtests, and all the items in each test were arranged in order of increasing difficulty. An equivalent alternate form of the test, the W-B II, was created in 1942 but was never thoroughly standardized (Rapaport et al., 1968).
Research comparing the W-B to other intelligence tests of the day suggested that the W-B measured something comparable to what other intelligence tests measured. Still, the test suffered from some problems:
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(1) The standardization sample was rather restricted;
(2) some subtests lacked sufficient inter-item reliability;
(3) some of the subtests were made up of items that were too easy; and
(4) the scoring criteria for certain items were too ambiguous.
Sixteen years after the publication of the W-B, a new
Wechsler scale for adults was published: the Wechsler
Adult Intelligence Scale (WAIS; Wechsler, 1955).
Like the W-B, the WAIS was organized into Verbal and Performance scales. Scoring yielded a Verbal IQ, a Performance IQ, and a Full Scale IQ. However, as a result of many improvements over its W-B predecessor, the WAIS would quickly achieve the status as “the standard against which other adult tests can be compared” (Lyman, 1972, p. 429).
Wechsler scale for adults was published: the Wechsler
Adult Intelligence Scale (WAIS; Wechsler, 1955).
Like the W-B, the WAIS was organized into Verbal and Performance scales. Scoring yielded a Verbal IQ, a Performance IQ, and a Full Scale IQ. However, as a result of many improvements over its W-B predecessor, the WAIS would quickly achieve the status as “the standard against which other adult tests can be compared” (Lyman, 1972, p. 429).
A revision of the WAIS, the WAIS-R, was published in 1981 shortly after Wechsler’s death in May of that same year. In addition to new norms and updated materials, the WAIS-R test administration manual mandated the alternate administration of verbal and performance tests. In 1997, the third edition of the test (the WAIS-III) was published, with authorship credited to David Wechsler.
The WAIS-III contained updated and more user -friendly materials. In some cases, test materials were made physically larger to facilitate viewing by older adults. Some items were added to each of the subtests that extended the test’s floor in order to make the test more useful for evaluating people with extreme intellectual deficits. Extensive research was designed to detect and eliminate items that may have contained cultural bias. Norms were expanded to include test takers in the age range of 74 to 89. The test was co-normed with the Wechsler Memory Scale-Third Edition (WMS-III), thus facilitating comparisons of memory with other indices of intellectual functioning when both the WAIS-III and the WMS-III were administered. The WAIS-III yielded a Full Scale (composite) IQ as well as four Index Scores -Verbal Comprehension, Perceptual Organization, Working Memory, and Processing Speed—used for more in-depth interpretation of findings.
The WAIS-III contained updated and more user -friendly materials. In some cases, test materials were made physically larger to facilitate viewing by older adults. Some items were added to each of the subtests that extended the test’s floor in order to make the test more useful for evaluating people with extreme intellectual deficits. Extensive research was designed to detect and eliminate items that may have contained cultural bias. Norms were expanded to include test takers in the age range of 74 to 89. The test was co-normed with the Wechsler Memory Scale-Third Edition (WMS-III), thus facilitating comparisons of memory with other indices of intellectual functioning when both the WAIS-III and the WMS-III were administered. The WAIS-III yielded a Full Scale (composite) IQ as well as four Index Scores -Verbal Comprehension, Perceptual Organization, Working Memory, and Processing Speed—used for more in-depth interpretation of findings.
The test today: The WAIS-IV is the most recent edition to the family of Wechsler adult scales. It is made up of subtests that are designated either as core or supplemental . A core subtest is one that is administered to obtain a composite score. Under usual circumstances, a supplemental subtest (also sometimes referred to as an optional subtest ) is used for purposes such as providing additional clinical information or extending the number of abilities or processes sampled. There are, however, situations in which a supplemental subtest can be used in place of a core subtest. The latter types of situation arise when, for some reason, the use of a score on a particular core subtest would be questionable. So, for example, a supplemental subtest might be substituted for a core subtest if:
■ the examiner incorrectly administered a core subtest
■ the assessee had been inappropriately exposed to the subtest items prior to their administration
■ the assessee evidenced a physical limitation that affected the assessee’s ability to effectively respond to the items of a particular subtest
More details of subtests click:
Reliability of the WISC-IV
When the WISC-IV was revised, developers intended to maintain the strong psychometric properties of its predecessors, which they largely did. The procedure for calculating reliability coefficients for the WISC-IV was analogous to that used for the WISC-III and WAIS-IV. Split-half reliabilities for the WISC-IV composites range from .88 for processing speed to .97 for the FSIQ (Wechsler,2003, p.35). Naturally, reliabilities for individual subtests run lower, as in all forms of tests.
When the WISC-IV was revised, developers intended to maintain the strong psychometric properties of its predecessors, which they largely did. The procedure for calculating reliability coefficients for the WISC-IV was analogous to that used for the WISC-III and WAIS-IV. Split-half reliabilities for the WISC-IV composites range from .88 for processing speed to .97 for the FSIQ (Wechsler,2003, p.35). Naturally, reliabilities for individual subtests run lower, as in all forms of tests.
WISC-IV Validity
In providing evidence of its validity, the WISC-IV manual relies on the modern trend that rejects the distinction between various types of validity and instead examines all of the relevant evidence that indicates whether a test score measures what it purports to (Wechsler, 2003, p. 47). The manual presents several lines of evidence of the test’s validity, involving theoretical considerations, the test’s internal structure, a variety of inter correlational studies, factor analytic studies, and evidence based on WISC-IV relationship with a host of other measures. As with its main competitor, the Binet, the WISC-IV manual presents extensive and comprehensive support for its validity.
In providing evidence of its validity, the WISC-IV manual relies on the modern trend that rejects the distinction between various types of validity and instead examines all of the relevant evidence that indicates whether a test score measures what it purports to (Wechsler, 2003, p. 47). The manual presents several lines of evidence of the test’s validity, involving theoretical considerations, the test’s internal structure, a variety of inter correlational studies, factor analytic studies, and evidence based on WISC-IV relationship with a host of other measures. As with its main competitor, the Binet, the WISC-IV manual presents extensive and comprehensive support for its validity.
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