WISC-R

The Wechsler Intelligence Scale for Children (WISC), developed by David Wechsler, is an individually administered intelligence test for children between the ages of 6 and 16. The Fifth Edition (WISC-V; Wechsler, 2014) is the most current version.

The WISC-V takes 45–65 minutes to administer and generates a Full Scale IQ (formerly known as an intelligence quotient or IQ score) which represents a child's general intellectual ability. It also provides five primary index scores (i.e., Verbal Comprehension Index, Visual Spatial Index, Fluid Reasoning Index, Working Memory Index, and Processing Speed Index) that represent a child's abilities in more discrete cognitive domains. Five ancillary composite scores can be derived from various combinations of primary or primary and secondary subtests.

Five complementary subtests yield three complementary composite scores to measure related cognitive abilities relevant to assessment and identification of specific learning disabilities, particularly dyslexia and dyscalculia. Variation in testing procedures and goals can reduce time of assessment to 15–20 minutes for the assessment of a single primary index, or increase testing time to three or more hours for a complete assessment, including all primary, ancillary, and complementary indices.

The original WISC (Wechsler, 1949) was an adaption of several of the subtests which made up the Wechsler–Bellevue Intelligence Scale (Wechsler, 1939) but also featured several subtests designed specifically for it. The subtests were organized into Verbal and Performance scales, and provided scores for Verbal IQ (VIQ), Performance IQ (PIQ), and Full Scale IQ (FSIQ).

Each successive edition has re-normed the test to compensate for the Flynn effect, ensuring not only that the norms do not become outdated which is suggested to result in inflated scores on intelligence measures, but that they are representative of the current population (Flynn, 1984, 1987, 1999; Matarazzo, 1972). Additional updates and refinements include changes to the questions to make them less biased against minorities and females, and updated materials to make them more useful in the administration of the test. A revised edition was published in 1974 as the WISC-R (Wechsler, 1974), featuring the same subtests however the age range was changed from 5-15 to 6-16.

The third edition was published in 1991 (WISC-III; Wechsler, 1991) and brought with it a new subtest as a measure of processing speed. In addition to the traditional VIQ, PIQ, and FSIQ scores, four new index scores were introduced to represent more narrow domains of cognitive function: the Verbal Comprehension Index (VCI), the Perceptual Organization Index (POI), the Freedom from Distractibility Index (FDI), and the Processing Speed Index (PSI).

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