Wechsler Intelligence Scales

The Wechsler Intelligence Scales are individually administered, standardized assessments of cognitive functioning. There are three Wechsler intelligence batteries, each designed for different age ranges: the Wechsler Preschool and Primary Scales of Intelligence (WPPSI), the Wechsler Intelligence Scales for Children (WISC), and the Wechsler Adult Intelligence Scales (WAIS). In 1939, the first test published by David Wechsler was intended for adults and was called the Wechsler–Bellevue. In 1955, the Wechsler–Bellevue became the first version of the WAIS. The first version of the WISC was developed in 1949, and the first version of the WPPSI was developed in 1967. With each revision of the Wechsler Scales, the subtests have been updated, new tests have been introduced, other tests have been removed, and changes have been made to the organization of the composite scores based on theory and research. Many of the subtests from the original Wechsler–Bellevue, though now different in item content, continue to be used on the current versions of the tests.

The Wechsler Scales provide scores for general intelligence and several other cognitive abilities, including verbal comprehension, fluid reasoning, visual spatial, working memory, and processing speed. There are also a number of ancillary composites included on the fourth edition of the WPPSI (WPPSI-IV), published in 2012, and the fifth edition of the WISC (WISC-V), published in 2014, that may enhance clinical interpretation. These ancillary composites include quantitative reasoning, vocabulary acquisition, and a nonverbal index that include tests that reduce the influence of expressive language. The Wechsler Scales provide age-based standard scores for composites (mean of 100, standard deviation of 15), age-based scaled scores for subtests (mean of 10, standard deviation of 3), and percentile ranks for all subtests and composites.

Each of the Wechsler batteries are used for a different age-group, although there is some slight overlap among the different tests (e.g., a 16-year-old may be administered the WISC-V or the WAIS-IV). The WPPSI-IV may be used for individuals between the ages of 2 years 6 months and 7 years 7 months, the WISC-V can be used with individuals between the ages of 6 years 0 months and 16 years 11 months, and the WAIS-IV may be used with individuals between the ages of 16 and 90 years. The normative sample for each test was large and representative of the U.S. population, including 1,700 children for the WPPSI-IV, 2,200 children and adolescents for the WISC-V, and 2,200 adolescents and adults for the WAIS-IV. The entry reviews the various composites and subtests as well as the scales’ psychometric properties.