The original WAIS (Form I) was published in February 1955 by David Wechsler, Chief Psychologist at Bellevue Hospital (1932–1967) in NYC, as a revision of the Wechsler–Bellevue Intelligence Scale released in 1939.[2] It is currently in its fifth edition (WAIS-5), released in 2024 by Pearson. It is the most widely used IQ test, for both adults and older adolescents, in the world.[3][4]
History
The WAIS was founded to get to know Wechsler's patients at Bellevue Hospital and on his definition of intelligence, which he defined as "... the global capacity of a person to act purposefully, to think rationally, and to deal effectively with his environment."[5] He believed that intelligence was made up of specific elements that could be isolated, defined, and subsequently measured. However, these individual elements were not entirely independent, but were all interrelated. His argument, in other words, is that general intelligence is composed of various specific and interrelated functions or elements that can be individually measured.[6]
This theory differed greatly from the Binet-Simon Intelligence Test which, in Wechsler's day, was generally considered the supreme authority with regard to intelligence testing. A drastically revised new version of the Binet scale, released in 1937, received a great deal of criticism from David Wechsler (after whom the original Wechsler–Bellevue Intelligence scale and the modern Wechsler Adult Intelligence Scale IV are named).[6]
Wechsler was a very influential advocate for the concept of non-intellective factors, and he felt that the 1937 Binet scale did not do a good job of incorporating these factors into the scale (non-intellective factors are variables that contribute to the overall score in intelligence, but are not made up of intelligence-related items. These include things such as lack of confidence, fear of failure, attitudes, etc.).
Wechsler did not agree with the idea of a single score that the Binet test gave.[6]
Wechsler argued that the Binet scale items were not valid for adult test-takers because the items were chosen specifically for use with children.[6]
The "Binet scale's emphasis on speed, with timed tasks scattered throughout the scale, tended to unduly handicap older adults."[6]
Wechsler believed that "mental age norms clearly did not apply to adults."[6]
Wechsler criticized the then existing Binet scale because "it did not consider that intellectual performance could deteriorate as a person grew older."[6]
These criticisms of the 1937 Binet test helped produce the Wechsler–Bellevue scale, released in 1939. However, the present-day WAIS-IV has contradicted many of these criticisms, by incorporating a single overall score, using multiple timed tasks, focusing on intellective items and other ways. While this scale has been revised (resulting in the present day WAIS-IV), many of the original concepts Wechsler argued for have become standards in psychological testing, including the point-scale concept and the performance-scale concept.[6]
Wechsler–Bellevue Intelligence Scale
The Wechsler–Bellevue tests were innovative in the 1930s because they:
gathered tasks created for nonclinical purposes for administration as a "clinical test battery",[7]
used the point scale concept instead of the age scale, and
In the Binet scales (prior to the 1986 version) items were grouped according to age level. Each of these age levels was composed of a group of tasks that could be passed by two-thirds to three-quarters of the individuals in that level. This meant that items were not arranged according to content. Additionally, an individual taking a Binet test would only receive credit if a certain number of the tasks were completed. This meant that falling short just one task required for the credit, resulted in no credit at all (for example, if passing three out of four tasks was required to receive credit, then passing two yielded no credit).[6]
The point scale concept significantly changed the way testing was done by assigning credits or points to each item. This had two large effects. First, this allowed items to be grouped according to content. Second, participants were able to receive a set number of points or credits for each item passed.[9] The result was a test that could be made up of different content areas (or subtests) with both an overall score and a score for each content area. In turn, this allowed for an analysis to be made of an individual's ability in a variety of content areas (as opposed to one general score).[6]
The Non-Verbal Performance Scale
The non-verbal performance scale was also a critical difference from the Binet scale. The earlier Binet scale had been persistently and consistently criticized for its emphasis on language and verbal skills.[6] Wechsler designed an entire scale that allowed the measurement of non-verbal intelligence. This became known as a performance scale. This scale required a subject to actively do something, such as copying symbols or pointing to a missing detail in a picture, rather than just answering questions. This was an important development, as it attempted to overcome biases that were caused by "language, culture, and education."[6] Further, this scale also provided an opportunity to observe a different type of behavior, because something physical was required. Clinicians were able to observe how a participant reacted to the "longer interval of sustained effort, concentration, and attention" that the performance tasks required.[6]
As the Wechsler–Bellevue scale was the first to effectively use the performance scale, it also introduced the "possibility of directly comparing an individual's verbal and nonverbal intelligence".[6] This was possible as "the results of both scales were expressed in comparable units".[6] The Binet scale did have performance tasks, but they were geared toward younger children. The Wechsler-Bellevue was also unique in that there were entire tests that were considered supplements or alternatives, including "performance" measures such as the Leiter International Performance Scale.[6]
WAIS
The WAIS was initially created as a revision of the Wechsler–Bellevue Intelligence Scale (WBIS), which was a battery of tests published by Wechsler in 1939. The WBIS was composed of subtests that could be found in various other intelligence tests of the time, such as Robert Yerkes' army testing program and the Binet-Simon scale. The WAIS was first released in February 1955 by David Wechsler. Because the Wechsler tests included non-verbal items (known as performance scales) as well as verbal items for all test-takers, and because the 1960 form of Lewis Terman's Stanford–Binet Intelligence Scales was less carefully developed than previous versions, Form I of the WAIS surpassed the Stanford–Binet tests in popularity by the 1960s.[2]
WAIS-R
Cubes and a target pattern of the WAIS-R's "Block Design" test
The WAIS-R, a revised form of the WAIS, was released in 1981 and consisted of six verbal and five performance subtests. The verbal tests were: Information, Comprehension, Arithmetic, Digit Span, Similarities, and Vocabulary. The Performance subtests were: Picture Arrangement, Picture Completion, Block Design, Object Assembly, and Digit Symbol. A verbal IQ, performance IQ and full scale IQ were obtained.[10]
This revised edition did not provide new validity data, but used the data from the original WAIS; however new norms were provided, carefully stratified.[10]
The WAIS-III, a subsequent revision of the WAIS and the WAIS-R, was released in 1997. It provided scores for Verbal IQ, Performance IQ, and Full Scale IQ, along with four secondary indices (Verbal Comprehension, Working Memory, Perceptual Organization, and Processing Speed). Some new contributors to the third edition of the most commonly used test of intellectual abilities include Hsin‐Yi Chen, Louise O’Donnell, Mark Ledbetter, David Tulsky, and Jianjun Zhu.[11]
Verbal IQ (VIQ)
Included seven tests and provided two sub-indices; verbal comprehension and working memory.
The Verbal Comprehension Index (VCI) included the following tests:
Information
Similarities
Vocabulary
The Working Memory Index (WMI) included:
Arithmetic
Digit Span
Letter-Number-Sequencing
Subtest(s) not included in the sub-indices:
Comprehension
Supplementary subtest(s) (Only to be used for total VIQ index scoring and specified sub-index):
Letter-Number-Sequencing
Performance IQ (PIQ)
Included six tests and it also provided two sub-indices; perceptual organization and processing speed.
The current version of the test, the WAIS-IV, which was released in 2008, is composed of 10 core subtests and five supplemental subtests, with the 10 core subtests yielding scaled scores that sum to derive the Full Scale IQ. With the WAIS-IV, the verbal/performance IQ scores from previous versions were removed and replaced by the index scores. The General Ability Index (GAI) was included, which consists of the Similarities, Vocabulary and Information subtests from the Verbal Comprehension Index and the Block Design, Matrix Reasoning and Visual Puzzles subtests from the Perceptual Reasoning Index. The GAI is clinically useful because it can be used as a measure of cognitive abilities that are less vulnerable to impairments of processing speed and working memory. There are several notable features in this version of the intelligence scale that make it unique from previous versions. Some of these changes include the removal of Picture Arrangement, Object Assembly, Mazes, Verbal IQ, and Performance IQ and the addition of five subtests that emphasize fluid reasoning and/or working memory.[3]
Index scores and scales
There are four index scores representing major components of intelligence:[3]
Verbal Comprehension Index (VCI)
Perceptual Reasoning Index (PRI)
Working Memory Index (WMI)
Processing Speed Index (PSI)
Two broad scores, which can be used to summarize general intellectual ability, can also be derived:
Full Scale IQ (FSIQ), based on the total combined performance of the VCI, PRI, WMI, and PSI. The WAIS-IV can generate an FSIQ in the range of 40 to 160.
General Ability Index (GAI), based only on the six subtests that the VCI and PRI comprise; it is intended to portray a snapshot of general intelligence that is less influenced by working memory and processing speed demands.
WAIS-IV subtests grouped by index
Index
Subtest
Core?
Description
Proposed abilities measured
Verbal Comprehension
Similarities
Describe how two words or concepts are similar.
Abstract verbal reasoning; semantic knowledge
Vocabulary
Name objects in pictures or define words presented to them.
Semantic knowledge; verbal comprehension and expression
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.
Visual spatial processing and problem solving; visual motor construction
Matrix Reasoning
View an array of pictures with one missing square, and select the picture that fits the array from five options.
Scan arrangements of shapes and mark specific target shapes within a limited amount of time
Processing speed
Standardization
The WAIS-IV was standardized on a sample of 2,200 people in the United States, ranging in age from 16 to 90.[12] The demographic characteristics of the sample were modeled after the proportions of different groups in an analysis of data from the U.S. Census Bureau. An extension of the standardization has been conducted with 688 Canadians in the same age range.
WAIS-5
The fifth edition of the Wechsler Adult Intelligence Scale is slated to be released in late 2024. Normative data were collected in 2023–24 on a U.S. Census-reflective sample that was conormed on the Wechsler Memory Scale: Fifth Edition.
The WAIS-5 introduces several new subtests, particularly in the working memory domain, with Digit Span Sequencing and Running Digits now being the core subtests that compose the Working Memory Index. Digit Span Forward, Digit Span Backward, and Letter-Number Sequencing may also be used to construct the Expanded Working Memory Index.
The Perceptual Reasoning Index has been split into Visual Spatial Ability (Block Design, Visual Puzzles) and Fluid Reasoning (Matrix Reasoning, Figure Weights). A complementary Fluid Reasoning subtest Set Relations was also introduced, as well as an additional Processing Speed subtest Naming Speed Quantity, which was originally featured in the WISC-V.
The Full Scale Intelligence Quotient is now generated from only seven subtests (Similarities, Vocabulary, Block Design, Matrix Reasoning, Figure Weights, Digit Span Sequencing, Coding), similar to the WISC-V. Fifteen ancillary index scores, including the General Ability Index, are also present.
Administration is anticipated to be shorter than the WAIS-IV, especially for those who are suspected as being intellectually gifted. The test may be administered in the classic physical format or on a digital platform.[13]
Intelligence tests may be used to assess the level of cognitive functioning in individuals with psychiatric illness or brain injury. Rehabilitation psychologists and neuropsychologists use neuropsychological tests (including the WAIS-IV) to assess how the individual's brain is functioning after it has been injured. Specific subtests can provide insight into specific cognitive functions; for example, the digit span subtest could be used to look for attentional difficulties.[14]
"WASI" redirects here. For the system interface for WebAssembly, see Webassembly §WASI.
The Wechsler Abbreviated Scale of Intelligence – 2nd edition (WASI-II) is a short psychological test that was developed in 2011 by Pearson to estimate intellectual functioning in a shorter period of time than the WAIS-IV.[18] The WASI-II only has 4 subtests: Block Design, Vocabulary, Similarities, and Matrix Reasoning, compared to the 10 core subtests that are present in the WAIS-IV. These 4 subtests have the same structure as the similarly-named subtests on the WAIS-IV, but have different questions.
The WASI-II can derive 4 composite scores from a combination of the 4 subtests. A Verbal Comprehension Index (VCI) can be derived from the raw scores on the Vocabulary and Similarities subtests. A Perceptual Reasoning Index (PRI) can be derived from the raw scores on the Matrix Reasoning and Block Design subtests. A Full Scale IQ-2 (FSIQ-2) can be derived from the raw scores on the Matrix Reasoning and Vocabulary subtests, while a Full Scale IQ-4 (FSIQ-4) can be derived from the raw scores on all 4 subtests.
WASI-II Subtests grouped by index
Index
Subtest
Description
Proposed abilities measured
Verbal Comprehension
Similarities
Describe how two words or concepts are similar.
Abstract verbal reasoning; semantic knowledge
Vocabulary
Name objects in pictures or define words presented to them.
Semantic knowledge; verbal comprehension and expression
Perceptual Reasoning
Block Design
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.
Visual spatial processing and problem solving; visual motor construction
Matrix Reasoning
View an array of pictures with one missing square, and select the picture that fits the array from five options.
An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence. Originally, IQ was a score obtained by dividing a person's mental age score, obtained by administering an intelligence test, by the person's chronological age, both expressed in terms of years and months. The resulting fraction (quotient) was multiplied by 100 to obtain the IQ score. For modern IQ tests, the raw score is transformed to a normal distribution with mean 100 and standard deviation 15. This results in approximately two-thirds of the population scoring between IQ 85 and IQ 115 and about 2 percent each above 130 and below 70.
The Stanford–Binet Intelligence Scales is an individually administered intelligence test that was revised from the original Binet–Simon Scale by Alfred Binet and Théodore Simon. It is in its fifth edition (SB5), which was released in 2003.
David "Weshy" Wechsler was a Romanian-American psychologist. He developed well-known intelligence scales, such as the Wechsler Adult Intelligence Scale (WAIS) and the Wechsler Intelligence Scale for Children (WISC) to get to know his patients at Bellevue Hospital. A Review of General Psychology survey, published in 2002, ranked Wechsler as the 51st most cited psychologist of the 20th century.
Cognitive tests are assessments of the cognitive capabilities of humans and other animals. Tests administered to humans include various forms of IQ tests; those administered to animals include the mirror test and the T maze test. Such testing is used in psychology and psychometrics, as well as other fields studying human and animal intelligence.
The Wechsler Intelligence Scale for Children (WISC) is an individually administered intelligence test for children between the ages of 6 and 16. The Fifth Edition is the most recent version.
Alan S. Kaufman is an American psychologist, writer, and research professor known for his work on intelligence testing.
Verbal reasoning is understanding and reasoning using concepts framed in words. It aims at evaluating ability to think constructively, rather than at simple fluency or vocabulary recognition.
The Wechsler Preschool and Primary Scale of Intelligence (WPPSI) is an intelligence test designed for children ages 2 years 6 months to 7 years 7 months developed by David Wechsler in 1967. It is a descendant of the earlier Wechsler Adult Intelligence Scale and the Wechsler Intelligence Scale for Children tests. Since its original publication the WPPSI has been revised three times in 1989, 2002, and 2012. The latest version, WPPSI–IV, published by Pearson Education, is a revision of the WPPSI-R and the WPPSI-III. It provides subtest and composite scores that represent intellectual functioning in verbal and performance cognitive domains, as well as providing a composite score that represents a child's general intellectual ability.
The Kaufman Assessment Battery for Children (KABC) is a clinical instrument for assessing cognitive development. Its construction incorporates several recent developments in both psychological theory and statistical methodology. The test was developed by Alan S. Kaufman and Nadeen L. Kaufman in 1983 and revised in 2004. The test has been translated and adopted for many countries, such as the Japanese version of the K-ABC by the Japanese psychologists Tatsuya Matsubara, Kazuhiro Fujita, Hisao Maekawa, and Toshinori Ishikuma.
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IQ classification is the practice of categorizing human intelligence, as measured by intelligence quotient (IQ) tests, into categories such as "superior" and "average".
The Cognitive Abilities Test (CogAT) is a group-administered K–12 assessment published by Riverside Insights and intended to estimate students' learned reasoning and problem solving abilities through a battery of verbal, quantitative, and nonverbal test items. The test purports to assess students' acquired reasoning abilities while also predicting achievement scores when administered with the co-normed Iowa Tests. The test was originally published in 1954 as the Lorge-Thorndike Intelligence Test, after the psychologists who authored the first version of it, Irving Lorge and Robert L. Thorndike. The CogAT is one of several tests used in the United States to help teachers or other school staff make student placement decisions for gifted education programs, and is accepted for admission to Intertel, a high IQ society for those who score at or above the 99th percentile on a test of intelligence.
Ammons Quick Test (QT) is an intelligence test that was designed in 1962 by Robert B. Ammons and his wife Carol H. Ammons. This test has been used for many years to help assess premorbid intelligence. It is a passive response picture-vocabulary test.
The Wechsler Individual Achievement Test Second Edition 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. The WIAT-II is a revision of the original WIAT, and additional measures. There are four basic scales: Reading, Math, Writing and Oral Language. Within these scales there is a total of 9 sub-test scores.
The following outline is provided as an overview of and topical guide to human intelligence:
The Snijders-Oomen nonverbal intelligence tests, shortly the SON-tests, are intelligence tests appropriate for children and adults from two and a half to forty years old. The tests are called nonverbal because they can be administered without having to use written or spoken language. The manuals also contain verbal instructions, but the spoken text does not contain extra information compared to the non-verbal instructions. The way the tests are administered is adjusted to the communicative abilities of the subject in order to create a natural test situation. The tests provide an intelligence score that indicates how someone performs in comparison with other persons from the same age.
The Wechsler Test of Adult Reading (WTAR) is a neuropsychological assessment tool used to provide a measure of premorbid intelligence, the degree of Intellectual function prior to the onset of illness or disease.
Verbal intelligence is the ability to understand and reason using concepts framed in words. More broadly, it is linked to problem solving, abstract reasoning, and working memory. Verbal intelligence is one of the most g-loaded abilities.
The Multidimensional Aptitude Battery II is a group-administered intelligence test created by psychologist Douglas N. Jackson which is supposed to measure Verbal, Performance and Full Scale IQ. The battery consists of 10 subtests and is used for various professional, medical, military, government, law enforcement and employment settings. The test-retest reliability based on timed performance correlates with values of 0.95 for the verbal section, 0.96 for the performance section and 0.97 for the full scale.
The Wide Range Intelligence test (WRIT) is an assessment of verbal (crystallized) and visual (fluid) IQ. Running at approximately 30 minutes, the WRIT is shorter than traditional IQ tests. The test also involves only four subtests and requires fewer physical materials than a typical test. It was created alongside the Wide Range Achievement Test 3 (WRAT3), a measure of reading comprehension and academic ability, by Pearson Education in 2000. The WRIT is intended to assess those aged 4 through 85. It is designed for easy administration among trained psychologists, which is accomplished using a hierarchical model that frequently occurs in psychological testing.
↑ Kaufman, Alan S. (2009). IQ Testing 101. New York: Springer Publishing. p.112. ISBN978-0-8261-0629-2.Sattler, Jerome M. (2008). Assessment of Children: Cognitive Foundations. La Mesa (CA): Jerome M. Sattler, publisher. inside back cover. ISBN978-0-9702671-4-6.
↑ Kaplan, R. M.; Saccuzzo, D. P. (2009). Psychological testing: Principles, applications, and issues (7thed.). Belmont, CA: Wadsworth.
↑ Silva, Paulo G. R.; Huijsing, Johan H., eds. (2008), "Introduction", High-Resolution If-To-Baseband ΣΔ Adc For Car Radios, Analog Circuits And Signal Processing, Dordrecht: Springer Netherlands, pp.1–9, doi:10.1007/978-1-4020-8164-4_1, ISBN978-1-4020-8164-4, retrieved 3 December 2023
Weiss, Lawrence G.; Saklofske, Donald H.; Coalson, Diane; Raiford, Susan, eds. (2010). WAIS-IV Clinical Use and Interpretation: Scientist-Practitioner Perspectives. Practical Resources for the Mental Health Professional. Alan S. Kaufman (Foreword). Amsterdam: Academic Press. ISBN978-0-12-375035-8.
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