The Wechsler Adult Intelligence Scale evolved as an alternative to the popular Stanford-Binet Intelligence Test that for many years was the standard of intelligence testing by psychologists. Dr. David Wechsler, a clinical psychologist, perceived that there were gaps with the Standford-Binet test, particularly in that adult testing appeared to solely be an adaptation of the test developed for children, not a test specifically developed based on adults’ intellectual performance. In the development of this new form of testing, three scales were developed: The Wechsler Intelligence Scale-III (WAIS-III), the Wechsler Intelligence Scale for Children-III (WISC-III), and the Wechsler Preschool and Primary Scale of Intelligence-R (WPPSI-R). As the testing is implemented, it is constantly changing and evolving to make sure the test is current and reliable and valid.
The Wechsler Intelligence Scale-III (WAIS-III)
At the core of the Weschler intelligence tests is the concept that intelligence cannot be measured by a single variable, but that there are multiple performance measures of intelligence that must be reviewed to determine intelligence. The current test for adults is the Wechsler Intelligence Scale-III, a third revision of the test developed in 1955 and revised again in 1981. The third revision was created in 1997. Prior to the 1955 WAIS-III, Dr. David Wechsler developed and subsequently published the Wechsler-Bellevue Intelligence Scale in 1939.
The WAIS-III contains a variety of Verbal and Performance Scales that measure the multiple categories such as general knowledge and problem-solving skills. The primary categories measured are: verbal comprehension, working memory, perceptual organization, and processing speed. A total of 12 categories compile the test with two optional categories as part of the test. The test must be proctored and scored by a trained examiner, who after the test converts the raw scores on the test to a standard score. The final Performance IQ score and Verbal IQ score are then converted to obtain a Full Scale IQ score.
The most recent version of the Wechsler intelligence scale is the WAIS-IV. Released in 2008, a total of 10 tests comprise the heart of the exam. There are five additional subtests that can be included as part of the examination. The WAIS-IV was released after extensive standardization. While utilized for intelligence testing, the WAIS-IV can also be used to assess cognitive functioning.
The Wechsler Intelligence Scale for Children-V(WISC-III)
The WISC-V is the most current version the Wechsler Intelligence Scale geared towards the age group of children 6 to 16 and was published in 2014. Similar to the WAIS-IV, a Full Scale IQ is generated upon completion of the examination. There have been several revisions of the original WISC published in 1949, but at the core this adaptation has many similarities to the version taken by adults in that it is measuring both Performance IQ and Verbal IQ. The test is constantly re-evaluated to maintain validity and reliability. The current test contains 21 subtests. The five primary index scores that are found in this test include: verbal comprehension, visual-spatial, fluid reasoning, working memory, and processing speed. Again, while intelligence testing is the primary use, the WISC-V has also been used for other clinical reasons.
The Wechsler Preschool and Primary Scale of Intelligence-IV (WPPSI-R)
A later test in the suite of Wechsler testing, the initial WPPSI was developed in 1967 to measure intelligence in children from ages four to six. Subsequent versions of the test have expanded the age range of children being measured to incorporate a wider subset of children in early childhood. This test also measures Performance IQ and Verbal IQ to determine a Full Scale IQ of participants. The test is comprised of 14 subtests. As with other tests of child intelligence, there are limitations to this test and this should be taken into account when reviewing test results.
The Wechsler Adult Intelligence Scale was initially developed and implemented as a more robust alternative to the Stanford-Binet intelligence testing of adults. Since it’s original implementation, a suite of tests derived from the original have been created to encompass younger participants. The testing is constantly reviewed and revised to keep the subjects and testing current. The Wechsler suite of testing adds a nuanced view of intelligence and is a useful tool for clinicians.