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Individual differences |
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The Wechsler Intelligence Scale for Children (WISC), developed by David Wechsler, is an intelligence test for children between the ages of 6 and 16 inclusive that can be completed without reading or writing. The WISC generates an IQ score.
The WISC was originally developed as a downward extension of the Wechsler Adult Intelligence Scale in 1949. A revised edition (WISC-R) in 1974 as the WISC-R, and the third edition, the WISC-III in 1991. The current version, the WISC-IV, was produced in 2003. Each successive version has renormed the test to compensate for the Flynn effect, refined questions to make them less biased against minorities and females, and updated materials to make them more useful in the administration of the test.
The test comprises ten core subtests and five supplemental ones. The supplemental subtests are used to accommodate children in certain rare cases, or to make up for spoiled results which may occur from interruptions or other circumstances. Testers are allowed no more than two substitutions in any FSIQ test, or no more than one per index. These subtests then generate a Full Scale score (FSIQ,) and four composite scores known as indices: Verbal Comprehension (VCI,) Perceptual Reasoning (PRI,) Processing Speed (PSI) and Working Memory (WMI.)
The WISC is one of a family of Weschler intelligence scales. Subjects over 16 are tested with the Wechsler Adult Intelligence Scale (WAIS), and children ages three to seven years, three months are tested with the Wechsler Preschool and Primary Scale of Intelligence (WPPSI).
Each of the ten core subtests is given equal weighting towards full-scale IQ. There are three subtests for both VCI and PRI, thus they are given 30% weighting each; in addition, PSI and WMI are given weighting for their two subtests each.
The VCI's subtests are as follows:
- Vocabulary - straightforward questions over the meaning of words
- Similarities - asking how two concepts are alike
- Comprehension - questions about social situations or common concepts
- Information (supplemental) - general knowledge questions
- Word Reasoning (supplemental) - children are presented with one to three riddle-style clues and asked to determine what the tester is describing.
The PRI's subtests are as follows:
- Block Design - children put together red-and-white blocks in a pattern according to a displayed model. This is timed, and some of the more difficult puzzles award bonuses for speed.
- Picture Concepts - children are shown rows of pictures, and are asked to find a common bond with one picture in each row.
- Matrix Reasoning - children are shown an array of pictures with one missing square, and select the picture that fits the array from five options.
- Picture Completion (supplemental) - children are shown artwork of common objects with a missing part, and asked to identify the missing part by pointing and/or naming.
The WMI's subtests are as follows:
- Digit Span - children are orally given sequences of numbers and asked to repeat them, either as heard or in reverse order.
- Letter-Number Sequencing - children are orally given sequences of letters and numbers together, and asked to repeat them in both numerical order and alphabetical order.
- Arithmetic (supplemental) - orally administered arithmetic questions. Timed.
The PSI's subtests are as follows:
- Coding - children under 8 mark rows of shapes with different lines according to a code, children over 8 transcribe a digit-symbol code. Time-limited with bonuses for speed.
- Symbol Search - children are given rows of symbols and target symbols, and asked to mark whether or not the target symbols appear in each row.
- Cancellation (supplemental) - students are to mark lines through objects that do not belong in a page of randomly-arranged objects and one of orthogonally-arranged objects.
The WISC is used not only as an intelligence test, but as a clinical tool. Many practitioners use it to diagnose attention-deficit hyperactivity disorder (ADHD) and learning disabilities, for example. This is usually done through a process called pattern analysis, in which the various subtests' scores are compared to one another (ipsative scoring) and clusters of unusually low scores in relation to the others are searched for. David Wechsler himself suggested this in 1958 (Kaplan & Saccuzzo, 2005).
However, the research does not show this to be a very effective way to diagnosis ADHD or learning disabilities (Watkins, Kush, & Glutting, 1997). The vast majority of ADHD children do not display certain subscores substantially below others, and many children who display such patterns do not have ADHD. Other patterns for children with learning disabilities show a similar lack of usefulness of the WISC as a diagnostic tool (Ward, Ward, Hatt, Young, & Moller, 1995).
When diagnosing children, best practice suggests that a multi-test battery should be used as learning problems, attention, and emotional difficulties can have similar symptoms, co-occur, or influence each other. For example, children with learning difficulties can become emotionally distraught and thus have concentration difficulties, begin to exhibit behavior problems, or both. Children with ADD or ADHD may show learning difficulties because of their attentional problems or also have learning disorder or mental retardation (or have nothing else). In short, while diagnosis of any childhood or adult difficulty should never be made based on IQ alone (or interview, physician examination, parent report, other test etc. for that matter) the cognitive ability test can help rule out, in conjunction with other tests and sources of information, other explanations for problems, uncover co-morbid problems, and be a rich source of information when properly analyzed and care is taken to avoid relying simply on the single summary IQ score (Sattler, ?year).
The empirical consensus is that the WISC is best used as a tool to evaluate intelligence and not to diagnose ADHD or learning disabled children. However, many clinicians use it to compare a child's cognitive development to his or her actual school or social performance. Using this discrepancy and other sources of data, the WISC can contribute information concerning a child's psychological well-being.
WISC has been translated or adapted to many languages, and norms have been established for a number of countries, including Spanish, Portuguese (Brazil), Norwegian, Swedish, French (France and Canada), German (Germany, Austria and Switzerland), English (United States, Canada, United Kingdom), Welsh, Dutch, Japanese, Chinese (Hong Kong), Greek, Slovenian and Italian. Separate norms are established with each translation. (Norway uses the Swedish norms).
- Kaplan, R.M. & Saccuzzo, D.P. (2005). Psychological Testing: Principles, applications, and issues. Belmont, CA: Thomson Wadsworth.
- Ward, S.B., Ward, T. J., Hatt, C.V., Young, D.L, & Mollner, N.R. (1995). The incidence and utility of the ACID, ACIDS, and SCAD profiles in a referred population. Psychology in the Schools, 32(4), 267-276.
- Watkins, M.W., Kush, J., & Glutting, J.J. (1997). Discriminant and predictive validity of the WISC-III ACID profile among children with learning disabilities. Psychology in the Schools, 34(4), 309-319.
- Leiter International Performance Scale
- Wechsler Adult Intelligence Scale (WAIS)
- Wechsler Preschool and Primary Scale of Intelligence (WPPSI)
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