Wechsler Intelligence Scale for Children
Encyclopedia
The Wechsler Intelligence Scale for Children (WISC), developed by Dr. David Wechsler, is an individually administered intelligence test for children between the ages of 6 and 16 inclusive that can be completed without reading or writing. The WISC takes 65-80 minutes to administer and generates an IQ score
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...

 which represents a child’s general cognitive ability.

History

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). 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).

The current version, the WISC-IV, was produced in 2003 followed by the UK version in 2004. Each successive version has re-normed the test to compensate for the Flynn effect
Flynn effect
The Flynn effect is the name given to a substantial and long-sustained increase in intelligence test scores measured in many parts of the world. When intelligence quotient tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100...

. Ensuring not only that the norms do not become outdated which is suggested to result in inflated scores on intelligence measures, but that they are representative of the current population (Flynn, 1984, 1987, 1999;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.

Test format

The WISC is one of a family of Wechsler intelligence scales. Subjects 16 and over are tested with the Wechsler Adult Intelligence Scale
Wechsler Adult Intelligence Scale
The Wechsler Adult Intelligence Scale intelligence quotient tests are the primary clinical instruments used to measure adult and adolescent intelligence. The original WAIS was published in February 1955 by David Wechsler, as a revision of the Wechsler-Bellevue Intelligence Scale...

 (WAIS), and children ages three to seven years, three months are tested with the Wechsler Preschool and Primary Scale of Intelligence
Wechsler Preschool and Primary Scale of Intelligence
The Wechsler Preschool and Primary Scale of Intelligence is an intelligence test designed for children ages 2 years 6 months to 7 years 3 months developed by David Wechsler in 1967. It is a descendent of the earlier Wechsler Adult Intelligence Scale and the Wechsler Intelligence Scale for Children...

 (WPPSI). There is some overlap between tests, with children aged 7 being able to complete the WPPSI or the WISC-IV, and children aged 16 being able to complete the WISC-IV or the WAIS. Different floor and ceiling effects can be achieved using the different tests, allowing for a greater understanding of the child’s abilities or deficits. This means that a 16 year old child who has mental retardation may be tested using the WISC-IV so that the clinician may see the floor of their knowledge (the lowest level).

The WISC-IV is divided into fifteen subtests, ten of which formed part of the previous WISC III. The five new subtests include three core tests: Picture Concepts, Letter-Number Sequencing, Matrix Reasoning and two supplemental tests: Cancellation and Word Reasoning. 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. A total of five composite scores can be derived with the WISC–IV. The WISC-IV generates a Full Scale IQ (FSIQ) which represents overall cognitive ability, the four other composite scores are Verbal Comprehension index (VCI), Perceptual Reasoning Index (PRI), Processing Speed Index (PSI) and Working Memory Index (WMI).

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 WISC-IV also produces seven process scores on three subtests: block design, cancellation and digit span. These scores are intended to provide more detailed information on cognitive abilities that contribute to performance on the subtest. These scores do not contribute to the composite scores.

The VCI's subtests are as follows:
  • Vocabulary
    Vocabulary
    A person's vocabulary is the set of words within a language that are familiar to that person. A vocabulary usually develops with age, and serves as a useful and fundamental tool for communication and acquiring knowledge...

     - examinee is asked to define a provided word.
  • Similarities - asking how two words are alike/similar.
  • Comprehension
    Understanding
    Understanding is a psychological process related to an abstract or physical object, such as a person, situation, or message whereby one is able to think about it and use concepts to deal adequately with that object....

     - questions about social situations or common concepts.
  • Information
    Information
    Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...

     (supplemental) - general knowledge questions.
  • Word reasoning (supplemental)- a task involving clues that lead to a specific word, each clue adds more information about the object/word/concept.


The Verbal Comprehension Index is an overall measure of verbal concept formation (the child's ability to verbally reason) and is influenced by knowledge learned from the environment.

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 provided with a series of pictures presented in rows (either two or three rows) and asked to determine which pictures go together, one from 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 (formerly known as Freedom from Distractibility Index) subtests are as follows:
  • Digit Span - children are orally given sequences of numbers and asked to repeat them, either as heard and in reverse order.
  • Letter-Number Sequencing - children are provided a series of numbers and letters and asked to provide them back to the examiner in a predetermined order.
  • Arithmetic
    Arithmetic
    Arithmetic or arithmetics is the oldest and most elementary branch of mathematics, used by almost everyone, for tasks ranging from simple day-to-day counting to advanced science and business calculations. It involves the study of quantity, especially as the result of combining numbers...

     (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. The task is 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)- children scan random and structured arrangements of pictures and marks specific target pictures within a limited amount of time.

Psychometric properties

The WISC–IV US standardization sample consisted of 2,200 children between the ages of 6 and 16 years 11 months and the UK sample consisted of 780 children. Both standardizations included special group samples including the following: children identified as gifted, children with mild or moderate mental retardation
Mental retardation
Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...

, children with learning disorders (reading, reading/writing, math, reading/writing/math), children with ADHD, children with expressive and mixed receptive-expressive language disorders children with autistic disorder, children with Asperger’s syndrome, children with open or closed head injury, and children with motor impairment.

WISC–IV is also validated with measures of achievement, memory, adaptive behaviour, emotional intelligence, and giftedness. Equivalency studies were also conducted within the Wechsler family of tests enabling comparisons between various Wechsler scores over the lifespan. A number of concurrent studies were conducted to examine the scale’s reliability and validity. Evidence of the convergent and discriminant validity of the WISC–IV is provided by correlational studies with the following instruments: WISC
WISC
WISC may refer to:* Wechsler Intelligence Scale for Children* WISC-TV, a television station licensed to Madison, Wisconsin, United States* Wisconsin Integrally Synchronized Computer* writable instruction set computer...

–III, WPPSI–III, WAIS
Wechsler Adult Intelligence Scale
The Wechsler Adult Intelligence Scale intelligence quotient tests are the primary clinical instruments used to measure adult and adolescent intelligence. The original WAIS was published in February 1955 by David Wechsler, as a revision of the Wechsler-Bellevue Intelligence Scale...

–III, WASI, WIAT
WIAT
WIAT, virtual channel 42, is the CBS-affiliated television station in the Birmingham/Tuscaloosa/Anniston/Gadsden, Alabama television market. Licensed to Birmingham, it broadcasts its digital signal on UHF channel 30, although through the use of PSIP, the station's virtual channel number is...

–II, CMS, GRS
Gifted Rating Scales
The Gifted Rating Scale is a scholastic assessment for school children. It is used mostly for Gifted & Talented admissions. It is administered by a teacher who knows the child well...

, BarOn EQ, and the ABAS–II. Evidence of construct validity was provided through a series of exploratory and confirmatory factor-analytic studies and mean comparisons using matched samples of clinical and nonclinical children.

Uses

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
Attention-deficit hyperactivity disorder
Attention deficit hyperactivity disorder is a developmental disorder. It is primarily characterized by "the co-existence of attentional problems and hyperactivity, with each behavior occurring infrequently alone" and symptoms starting before seven years of age.ADHD is the most commonly studied and...

 (ADHD) and learning disabilities
Learning disability
Learning disability is a classification including several disorders in which a person has difficulty learning in a typical manner, usually caused by an unknown factor or factors...

, for example. This is usually done through a process called pattern analysis, in which the various subtests' scores are compared to one another (ipsative
Ipsative
Ipsative is a descriptor used in psychology to indicate a specific type of measure in which respondents compare two or more desirable options and pick the one that is most preferred . This is contrasted with measures that use Likert-type scales, in which respondents choose the score Ipsative is a...

 scoring) and clusters of unusually low scores in relation to the others are searched for. David Wechsler himself suggested this in 1958.

However, the research does not show this to be a very effective way to diagnose ADHD or learning disabilities. 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.

When diagnosing children, best practice suggests that a multi-test battery (i.e., multi-factored evaluation) should be used as learning problems, attention, and emotional difficulties can have similar symptoms, co-occur, or reciprocally 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, 2008).

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. It can be used to show discrepancies between a child's intelligence and his/her performance at school (and it is this discrepancy that School Psychologists look for when using this test). In a clinical setting, learning disabilities are generally diagnosed through a comparison of intelligence scores and scores on an achievement test, such as the Woodcock Johnson III or Wechsler Individual Achievement Test II. If a child's achievement is below what would be expected given their level of intellectual functioning (as derived from an IQ test such as the WISC-IV), then a learning disability may be present.

Subsequently, the WISC can be used as part of an assessment battery to identify intellectual giftedness, learning difficulties, and cognitive strengths and weaknesses. When combined with other measures such as the Adaptive Behaviour Assessment System–II (ABAS–II; Harrison & Oakland, 2003) and the Children’s Memory Scale (CMS; Cohen, 1997) it’s clinical utility can be enhanced. Combinations such as these provide information on cognitive and adaptive functioning, both of which are required for the proper diagnosis of learning difficulties and learning and memory functioning resulting in a richer picture of a child’s cognitive functioning.

The WISC
WISC
WISC may refer to:* Wechsler Intelligence Scale for Children* WISC-TV, a television station licensed to Madison, Wisconsin, United States* Wisconsin Integrally Synchronized Computer* writable instruction set computer...

–IV has also been co normed with the Wechsler Individual Achievement Test
Wechsler Individual Achievement Test
The Wechsler Individual Achievement Test Second Edition developed by David Wechsler, assesses the academic achievement of children, adolescents, college students and adults, aged 4 through 85. The test enables the assessment of a broad range of academics skills or only a particular area of need...

-II UK (WIAT–II UK; The Psychological Corporation, 2005), a measure of academic achievement. This linkage provides information on both cognitive ability and academic achievement in children. Tests of intellectual functioning are used extensively in school settings to evaluate specific cognitive deficits that may contribute to low academic achievement, and to predict future academic achievement. Using the WISC–IV in such a manner provides information for educational intervention purposes, such as interventions that address learning difficulties and cognitive deficits.

The WISC-IV can also be used to assess a child's cognitive development, with respect to the child's chronological age. Using such comparisons with other sources of data, the WISC can contribute information concerning a child's developmental and psychological well-being. Very high or very low scores may suggest contributing factors for adjustment difficulties in social contexts that present problems in accepting such developmental diversity (or that cannot accommodate more than a certain level of high cognitive functioning.)

Translations

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, Finnish, Croatian, French (France and Canada), German (Germany, Austria and Switzerland), English (United States, Canada, United Kingdom, Australia), Welsh
Welsh language
Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

, Dutch
Dutch language
Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...

, Japanese, Chinese (Hong Kong), Korean (South Korea), Greek, Romanian, Slovenian and Italian. Separate norms are established with each translation. (Norway uses the Swedish norms). India uses the Malin's Intelligence Scale for Children (MISIC), an adaptation of WISC.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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