89-519: The Wechsler Adult Intelligence Scale ( WAIS ) is an IQ test designed to measure intelligence and cognitive ability in adults and older adolescents. For children between the ages of 6 and 16, Wechsler Intelligence Scale for Children (WISC) is commonly used. The original WAIS (Form I) was published in February 1955 by David Wechsler , Chief Psychologist at Bellevue Hospital (1932–1967) in NYC, as
178-418: A cohort effect rather than a true aging effect. A variety of studies of IQ and aging have been conducted since the norming of the first Wechsler Intelligence Scale drew attention to IQ differences in different age groups of adults. Both cohort effects (the birth year of the test-takers) and practice effects (test-takers taking the same form of IQ test more than once) must be controlled to gain accurate data. It
267-446: A normal distribution with mean 100 and standard deviation 15. While one standard deviation is 15 points, and two SDs are 30 points, and so on, this does not imply that mental ability is linearly related to IQ, such that IQ 50 would mean half the cognitive ability of IQ 100. In particular, IQ points are not percentage points. Psychometricians generally regard IQ tests as having high statistical reliability . Reliability represents
356-553: 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). 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
445-461: A common strength in abstract reasoning across the test's item content. During World War I, the Army needed a way to evaluate and assign recruits to appropriate tasks. This led to the development of several mental tests by Robert Yerkes , who worked with major hereditarians of American psychometrics—including Terman, Goddard—to write the test. The testing generated controversy and much public debate in
534-620: A concept of intelligence on IQ test scores alone neglects other important aspects of mental ability. Robert Sternberg , another significant critic of IQ as the main measure of human cognitive abilities, argued that reducing the concept of intelligence to the measure of g does not fully account for the different skills and knowledge types that produce success in human society. Despite these objections, clinical psychologists generally regard IQ scores as having sufficient statistical validity for many clinical purposes. Differential item functioning (DIF), sometimes referred to as measurement bias,
623-746: A merging of the Gf-Gc theory of Cattell and Horn with Carroll's Three-Stratum theory has led to the Cattell–Horn–Carroll theory (CHC Theory), with g as the top of the hierarchy, ten broad abilities below, and further subdivided into seventy narrow abilities on the third stratum. CHC Theory has greatly influenced many of the current broad IQ tests. Modern tests do not necessarily measure all of these broad abilities. For example, quantitative knowledge and reading and writing ability may be seen as measures of school achievement and not IQ. Decision speed may be difficult to measure without special equipment. g
712-464: A model of intelligence that included seven unrelated factors (verbal comprehension, word fluency, number facility, spatial visualization, associative memory, perceptual speed, reasoning, and induction). While not widely used, Thurstone's model influenced later theories. David Wechsler produced the first version of his test in 1939. It gradually became more popular and overtook the Stanford–Binet in
801-444: A particular stimulus, ignoring distractions, and maintaining vigilance. Simultaneous processing involves the integration of stimuli into a group and requires the observation of relationships. Successive processing involves the integration of stimuli into serial order. The planning and attention/arousal components comes from structures located in the frontal lobe, and the simultaneous and successive processes come from structures located in
890-514: A person to act purposefully, to think rationally, and to deal effectively with his environment." 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. This theory differed greatly from
979-460: 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
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#17327795901681068-399: A resurgence as a voluntary means of selective reproduction, with some calling them " new eugenics ". As it becomes possible to test for and correlate genes with IQ (and its proxies), ethicists and embryonic genetic testing companies are attempting to understand the ways in which the technology can be ethically deployed. Raymond Cattell (1941) proposed two types of cognitive abilities in
1157-422: A revision of Spearman's concept of general intelligence. Fluid intelligence (Gf) was hypothesized as the ability to solve novel problems by using reasoning, and crystallized intelligence (Gc) was hypothesized as a knowledge-based ability that was very dependent on education and experience. In addition, fluid intelligence was hypothesized to decline with age, while crystallized intelligence was largely resistant to
1246-489: A revision of the Wechsler–Bellevue Intelligence Scale released in 1939. 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. 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
1335-414: A set number of points or credits for each item passed. 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). The non-verbal performance scale was also a critical difference from
1424-463: A single general ability factor and a large number of narrow task-specific ability factors. Spearman named it g for "general factor" and labeled the specific factors or abilities for specific tasks s . In any collection of test items that make up an IQ test, the score that best measures g is the composite score that has the highest correlations with all the item scores. Typically, the " g -loaded" composite score of an IQ test battery appears to involve
1513-435: A six-year-old child who passed all the tasks usually passed by six-year-olds—but nothing beyond—would have a mental age that matched his chronological age, 6.0. (Fancher, 1985). Binet and Simon thought that intelligence was multifaceted, but came under the control of practical judgment. In Binet and Simon's view, there were limitations with the scale and they stressed what they saw as the remarkable diversity of intelligence and
1602-499: A strong consensus of mainstream science, though fringe figures continue to promote them in pseudo-scholarship and popular culture. Historically, even before IQ tests were devised, there were attempts to classify people into intelligence categories by observing their behavior in daily life. Those other forms of behavioral observation are still important for validating classifications based primarily on IQ test scores. Both intelligence classification by observation of behavior outside
1691-875: A total of 120 types of intelligence. It was popular in the 1970s and early 1980s, but faded owing to both practical problems and theoretical criticisms. Alexander Luria 's earlier work on neuropsychological processes led to the PASS theory (1997). It argued that only looking at one general factor was inadequate for researchers and clinicians who worked with learning disabilities, attention disorders, intellectual disability, and interventions for such disabilities. The PASS model covers four kinds of processes (planning process, attention/arousal process, simultaneous processing, and successive processing). The planning processes involve decision making, problem solving, and performing activities and require goal setting and self-monitoring. The attention/arousal process involves selectively attending to
1780-400: Is a hierarchical model with three levels. The bottom stratum consists of narrow abilities that are highly specialized (e.g., induction, spelling ability). The second stratum consists of broad abilities. Carroll identified eight second-stratum abilities. Carroll accepted Spearman's concept of general intelligence, for the most part, as a representation of the uppermost, third stratum. In 1999,
1869-571: Is a phenomenon when participants from different groups (e.g. gender, race, disability) with the same latent abilities give different answers to specific questions on the same IQ test. DIF analysis measures such specific items on a test alongside measuring participants' latent abilities on other similar questions. A consistent different group response to a specific question among similar types of questions can indicate an effect of DIF. It does not count as differential item functioning if both groups have an equally valid chance of giving different responses to
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#17327795901681958-606: 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
2047-603: Is now similar to the Wechsler in several aspects, but the Wechsler continues to be the most popular test in the United States. Eugenics , a set of beliefs and practices aimed at improving the genetic quality of the human population by excluding people and groups judged to be inferior and promoting those judged to be superior, played a significant role in the history and culture of the United States during
2136-487: Is set so performance at the population median results in a score of IQ 100. The phenomenon of rising raw score performance means if test-takers are scored by a constant standard scoring rule, IQ test scores have been rising at an average rate of around three IQ points per decade. This phenomenon was named the Flynn effect in the book The Bell Curve after James R. Flynn , the author who did the most to bring this phenomenon to
2225-597: Is unclear whether any lifestyle intervention can preserve fluid intelligence into older ages. Environmental and genetic factors play a role in determining IQ. Their relative importance has been the subject of much research and debate. The general figure for the heritability of IQ, according to an American Psychological Association report, is 0.45 for children, and rises to around 0.75 for late adolescents and adults. Heritability measures for g factor in infancy are as low as 0.2, around 0.4 in middle childhood, and as high as 0.9 in adulthood. One proposed explanation
2314-557: 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). These criticisms of
2403-531: The Binet–Simon Intelligence test , which focused on verbal abilities . It was intended to identify "mental retardation" in school children, but in specific contradistinction to claims made by psychiatrists that these children were "sick" (not "slow") and should therefore be removed from school and cared for in asylums. The score on the Binet–Simon scale would reveal the child's mental age . For example,
2492-751: The Progressive Era , from the late 19th century until US involvement in World War II . The American eugenics movement was rooted in the biological determinist ideas of the British Scientist Sir Francis Galton . In 1883, Galton first used the word eugenics to describe the biological improvement of human genes and the concept of being "well-born". He believed that differences in a person's ability were acquired primarily through genetics and that eugenics could be implemented through selective breeding in order for
2581-503: The Triple Nine Society . 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. 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
2670-603: The WAIS-R test may contain cultural influences that reduce the validity of the WAIS-R as a measure of cognitive ability for Mexican American students," indicating a weaker positive correlation relative to sampled white students. Other recent studies have questioned the culture-fairness of IQ tests when used in South Africa. Standard intelligence tests, such as the Stanford–Binet, are often inappropriate for autistic children;
2759-653: The correlations between it and other variables. Raw scores on IQ tests for many populations have been rising at an average rate that scales to three IQ points per decade since the early 20th century, a phenomenon called the Flynn effect . Investigation of different patterns of increases in subtest scores can also inform current research on human intelligence. Historically, many proponents of IQ testing have been eugenicists who used pseudoscience to push now-debunked views of racial hierarchy in order to justify segregation and oppose immigration . Such views are now rejected by
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2848-480: The heritability of IQ has been investigated for nearly a century, there is still debate about the significance of heritability estimates and the mechanisms of inheritance. IQ scores are used for educational placement, assessment of intellectual ability , and evaluating job applicants. In research contexts, they have been studied as predictors of job performance and income . They are also used to study distributions of psychometric intelligence in populations and
2937-436: The proximal development of children, originated in the writings of psychologist Lev Vygotsky (1896–1934) during his last two years of his life. According to Vygotsky, the maximum level of complexity and difficulty of problems that a child is capable to solve under some guidance indicates their level of potential development. The difference between this level of potential and the lower level of unassisted performance indicates
3026-517: 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
3115-456: The 1960s. It has been revised several times, as is common for IQ tests, to incorporate new research. One explanation is that psychologists and educators wanted more information than the single score from the Binet. Wechsler's ten or more subtests provided this. Another is that the Stanford–Binet test reflected mostly verbal abilities, while the Wechsler test also reflected nonverbal abilities. The Stanford–Binet has also been revised several times and
3204-446: The 95% confidence interval may be greater than 40 points, potentially complicating the accuracy of diagnoses of intellectual disability. By the same token, high IQ scores are also significantly less reliable than those near to the population median. Reports of IQ scores much higher than 160 are considered dubious. Reliability and validity are very different concepts. While reliability reflects reproducibility, validity refers to whether
3293-440: The Binet scale. The earlier Binet scale had been persistently and consistently criticized for its emphasis on language and verbal skills. 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
3382-513: 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
3471-464: The Flynn effect demolishes the fears that IQ would be decreased. He also asks whether it represents a real increase in intelligence beyond IQ scores. A 2011 psychology textbook, lead authored by Harvard Psychologist Professor Daniel Schacter , noted that humans' inherited intelligence could be going down while acquired intelligence goes up. Research has suggested that the Flynn effect has slowed or reversed course in some Western countries beginning in
3560-685: The Leiter International Performance Scale. 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
3649-447: The US eugenics movement to eliminate "undesirable" traits. Goddard used the term " feeble-minded " to refer to people who did not perform well on the test. He argued that "feeble-mindedness" was caused by heredity, and thus feeble-minded people should be prevented from giving birth, either by institutional isolation or sterilization surgeries. At first, sterilization targeted the disabled, but
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3738-456: The United States. Nonverbal or "performance" tests were developed for those who could not speak English or were suspected of malingering. Based on Goddard's translation of the Binet–Simon test, the tests had an impact in screening men for officer training: ...the tests did have a strong impact in some areas, particularly in screening men for officer training. At the start of the war, the army and national guard maintained nine thousand officers. By
3827-491: 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. The Wechsler tests can also be used to identify intellectual giftedness , and are commonly accepted as qualifying evidence for high-IQ societies , such as Mensa , Intertel and
3916-866: 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. 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. This revised edition did not provide new validity data, but used
4005-530: 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". This was possible as "the results of both scales were expressed in comparable units". 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
4094-404: The alternative of using developmental or adaptive skills measures are relatively poor measures of intelligence in autistic children, and may have resulted in incorrect claims that a majority of autistic children are of low intelligence. Since the early 20th century, raw scores on IQ tests have increased in most parts of the world. When a new version of an IQ test is normed, the standard scoring
4183-416: The attention of psychologists. Researchers have been exploring the issue of whether the Flynn effect is equally strong on performance of all kinds of IQ test items, whether the effect may have ended in some developed nations, whether there are social subgroup differences in the effect, and what possible causes of the effect might be. A 2011 textbook, IQ and Human Intelligence , by N. J. Mackintosh , noted
4272-648: The banner of dynamic assessment , which seeks to measure developmental potential (for instance, in the work of Reuven Feuerstein and his associates, who has criticized standard IQ testing for its putative assumption or acceptance of "fixed and immutable" characteristics of intelligence or cognitive functioning). Dynamic assessment has been further elaborated in the work of Ann Brown , and John D. Bransford and in theories of multiple intelligences authored by Howard Gardner and Robert Sternberg . J.P. Guilford 's Structure of Intellect (1967) model of intelligence used three dimensions, which, when combined, yielded
4361-448: The child's zone of proximal development. Combination of the two indexes—the level of actual and the zone of the proximal development—according to Vygotsky, provides a significantly more informative indicator of psychological development than the assessment of the level of actual development alone. His ideas on the zone of development were later developed in a number of psychological and educational theories and practices, most notably under
4450-713: The classic physical format or on a digital platform. The WAIS-IV measure is acceptable for use with people who are 16–90 years of age. For people younger than 16, the Wechsler Preschool and Primary Scale of Intelligence (WPPSI, 2½–7 years, 7 months) and the Wechsler Intelligence Scale for Children (WISC, 6–16 years) are used. 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
4539-719: The current versions of the Stanford–Binet Intelligence Scales , Woodcock–Johnson Tests of Cognitive Abilities , the Kaufman Assessment Battery for Children , the Cognitive Assessment System , and the Differential Ability Scales . There are various other IQ tests, including: IQ scales are ordinally scaled . The raw score of the norming sample is usually (rank order) transformed to
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#17327795901684628-411: The data from the original WAIS; however new norms were provided, carefully stratified. 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
4717-407: The early adulthood) while longitudinal data mostly show that intelligence is stable until mid-adulthood or later. Subsequently, intelligence seems to decline slowly. For decades, practitioners' handbooks and textbooks on IQ testing have reported IQ declines with age after the beginning of adulthood. However, later researchers pointed out this phenomenon is related to the Flynn effect and is in part
4806-400: The effects of aging. The theory was almost forgotten, but was revived by his student John L. Horn (1966) who later argued Gf and Gc were only two among several factors, and who eventually identified nine or ten broad abilities. The theory continued to be called Gf-Gc theory. John B. Carroll (1993), after a comprehensive reanalysis of earlier data, proposed the three stratum theory , which
4895-565: The end, two hundred thousand officers presided, and two- thirds of them had started their careers in training camps where the tests were applied. In some camps, no man scoring below C could be considered for officer training. In total 1.75 million men were tested, making the results the first mass-produced written tests of intelligence, though considered dubious and non-usable, for reasons including high variability of test implementation throughout different camps and questions testing for familiarity with American culture rather than intelligence. After
4984-416: The estimate. For modern tests, the confidence interval can be approximately 10 points and reported standard error of measurement can be as low as about three points. Reported standard error may be an underestimate, as it does not account for all sources of error. Outside influences such as low motivation or high anxiety can occasionally lower a person's IQ test score. For individuals with very low scores,
5073-411: The fallacy of reification , "our tendency to convert abstract concepts into entities". Gould's argument sparked a great deal of debate, and the book is listed as one of Discover Magazine ' s "25 Greatest Science Books of All Time". Along these same lines, critics such as Keith Stanovich do not dispute the capacity of IQ test scores to predict some kinds of achievement, but argue that basing
5162-422: The first formal factor analysis of correlations between the tests. He observed that children's school grades across seemingly unrelated school subjects were positively correlated, and reasoned that these correlations reflected the influence of an underlying general mental ability that entered into performance on all kinds of mental tests. He suggested that all mental performance could be conceptualized in terms of
5251-427: The first mental testing center in the world in 1882 and he published "Inquiries into Human Faculty and Its Development" in 1883, in which he set out his theories. After gathering data on a variety of physical variables, he was unable to show any such correlation, and he eventually abandoned this research. French psychologist Alfred Binet and psychiatrist Théodore Simon , had more success in 1905, when they published
5340-520: The human race to improve in its overall quality, therefore allowing for humans to direct their own evolution. Henry H. Goddard was a eugenicist. In 1908, he published his own version, The Binet and Simon Test of Intellectual Capacity , and cordially promoted the test. He quickly extended the use of the scale to the public schools (1913), to immigration ( Ellis Island , 1914) and to a court of law (1914). Unlike Galton, who promoted eugenics through selective breeding for positive traits, Goddard went with
5429-403: The idea that IQ heritability rises with age. Researchers building on this phenomenon dubbed it "The Wilson Effect," named after the behavioral geneticist. A paper by Thomas J. Bouchard Jr. , examining twin and adoption studies, including twins "reared apart," finds that IQ "reaches an asymptote at about 0.80 at 18–20 years of age and continuing at that level well into adulthood. In the aggregate,
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#17327795901685518-784: 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
5607-468: 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. There are four index scores representing major components of intelligence: Two broad scores, which can be used to summarize general intellectual ability, can also be derived: The WAIS-IV
5696-498: The kind of intelligence necessary to do well in academic work. But if the purpose is to assess intelligence in a broader sense, the validity of IQ tests is questionable." Some scientists have disputed the value of IQ as a measure of intelligence altogether. In The Mismeasure of Man (1981, expanded edition 1996), evolutionary biologist Stephen Jay Gould compared IQ testing with the now-discredited practice of determining intelligence via craniometry , arguing that both are based on
5785-402: The late 20th century. The phenomenon has been termed the negative Flynn effect . A study of Norwegian military conscripts' test records found that IQ scores have been falling for generations born after the year 1975, and that the underlying cause of both initial increasing and subsequent falling trends appears to be environmental rather than genetic. Ronald S. Wilson is largely credited with
5874-414: The mean scores of tests at ages 11, 12, and 13. The current consensus is that fluid intelligence generally declines with age after early adulthood, while crystallized intelligence remains intact. However, the exact peak age of fluid intelligence or crystallized intelligence remains elusive. Cross-sectional studies usually show that especially fluid intelligence peaks at a relatively young age (often in
5963-445: The measurement consistency of a test. A reliable test produces similar scores upon repetition. On aggregate, IQ tests exhibit high reliability, although test-takers may have varying scores when taking the same test on differing occasions, and may have varying scores when taking different IQ tests at the same age. Like all statistical quantities, any particular estimate of IQ has an associated standard error that measures uncertainty about
6052-723: The most commonly used test of intellectual abilities include Hsin‐Yi Chen, Louise O’Donnell, Mark Ledbetter, David Tulsky, and Jianjun Zhu. Included seven tests and provided two sub-indices; verbal comprehension and working memory . The Verbal Comprehension Index (VCI) included the following tests: The Working Memory Index (WMI) included: Subtest(s) not included in the sub-indices: Supplementary subtest(s) (Only to be used for total VIQ index scoring and specified sub-index): Included six tests and it also provided two sub-indices; perceptual organization and processing speed. The Perceptual Organization Index (POI) included: The Processing Speed Index (PSI) included: Subtest(s) not included in
6141-468: The point-scale concept and the performance-scale concept. The Wechsler–Bellevue tests were innovative in the 1930s because they: 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
6230-530: The population scoring between IQ 85 and IQ 115 and about 2 percent each above 130 and below 70 . Scores from intelligence tests are estimates of intelligence. Unlike, for example, distance and mass, a concrete measure of intelligence cannot be achieved given the abstract nature of the concept of "intelligence". IQ scores have been shown to be associated with such factors as nutrition , parental socioeconomic status , morbidity and mortality , parental social status , and perinatal environment . While
6319-727: The posterior region of the cortex. It has influenced some recent IQ tests, and been seen as a complement to the Cattell–Horn–Carroll theory described above. There are a variety of individually administered IQ tests in use in the English-speaking world. The most commonly used individual IQ test series is the Wechsler Adult Intelligence Scale (WAIS) for adults and the Wechsler Intelligence Scale for Children (WISC) for school-age test-takers. Other commonly used individual IQ tests (some of which do not label their standard scores as "IQ" scores) include
6408-471: 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 IQ test 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
6497-593: The same questions. Such bias can be a result of culture, educational level and other factors that are independent of group traits. DIF is only considered if test-takers from different groups with the same underlying latent ability level have a different chance of giving specific responses. Such questions are usually removed in order to make the test equally fair for both groups. Common techniques for analyzing DIF are item response theory (IRT) based methods, Mantel-Haenszel, and logistic regression . A 2005 study found that "differential validity in prediction suggests that
6586-523: 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
6675-430: The studies also confirm that shared environmental influence decreases across age, approximating about 0.10 at 18–20 years of age and continuing at that level into adulthood." IQ can change to some degree over the course of childhood. In one longitudinal study , the mean IQ scores of tests at ages 17 and 18 were correlated at r = 0.86 with the mean scores of tests at ages five, six, and seven and at r = 0.96 with
6764-426: The study of human diversity and the study of inheritance of human traits, he believed that intelligence was largely a product of heredity (by which he did not mean genes , although he did develop several pre-Mendelian theories of particulate inheritance). He hypothesized that there should exist a correlation between intelligence and other observable traits such as reflexes , muscle grip, and head size . He set up
6853-505: The sub-indices: Supplementary subtests (Only to be used for total PIQ index scoring and specified sub-index): 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
6942-597: The subsequent need to study it using qualitative, as opposed to quantitative, measures (White, 2000). American psychologist Henry H. Goddard published a translation of it in 1910. American psychologist Lewis Terman at Stanford University revised the Binet–Simon scale, which resulted in the Stanford revision of the Binet-Simon Intelligence Scale (1916). It became the most popular test in the United States for decades. The abbreviation "IQ"
7031-474: The test measures what it purports to measure. While IQ tests are generally considered to measure some forms of intelligence, they may fail to serve as an accurate measure of broader definitions of human intelligence inclusive of, for example, creativity and social intelligence . For this reason, psychologist Wayne Weiten argues that their construct validity must be carefully qualified, and not be overstated. According to Weiten, "IQ tests are valid measures of
7120-422: The testing room and classification by IQ testing depend on the definition of "intelligence" used in a particular case and on the reliability and error of estimation in the classification procedure. The English statistician Francis Galton (1822–1911) made the first attempt at creating a standardized test for rating a person's intelligence. A pioneer of psychometrics and the application of statistical methods to
7209-490: The war, positive publicity promoted by army psychologists helped to make psychology a respected field. Subsequently, there was an increase in jobs and funding in psychology in the United States. Group intelligence tests were developed and became widely used in schools and industry. The results of these tests, which at the time reaffirmed contemporary racism and nationalism, are considered controversial and dubious, having rested on certain contested assumptions: that intelligence
7298-426: Was an important development, as it attempted to overcome biases that were caused by "language, culture, and education." 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. As
7387-579: Was coined by the psychologist William Stern for the German term Intelligenzquotient , his term for a scoring method for intelligence tests at University of Breslau he advocated in a 1912 book. The many different kinds of IQ tests include a wide variety of item content. Some test items are visual, while many are verbal. Test items vary from being based on abstract-reasoning problems to concentrating on arithmetic, vocabulary, or general knowledge. The British psychologist Charles Spearman in 1904 made
7476-570: Was earlier often subdivided into only Gf and Gc, which were thought to correspond to the nonverbal or performance subtests and verbal subtests in earlier versions of the popular Wechsler IQ test. More recent research has shown the situation to be more complex. Modern comprehensive IQ tests do not stop at reporting a single IQ score. Although they still give an overall score, they now also give scores for many of these more restricted abilities, identifying particular strengths and weaknesses of an individual. An alternative to standard IQ tests, meant to test
7565-512: Was heritable, innate, and could be relegated to a single number, the tests were enacted systematically, and test questions actually tested for innate intelligence rather than subsuming environmental factors. The tests also allowed for the bolstering of jingoist narratives in the context of increased immigration, which may have influenced the passing of the Immigration Restriction Act of 1924 . L.L. Thurstone argued for
7654-487: Was later extended to poor people. Goddard's intelligence test was endorsed by the eugenicists to push for laws for forced sterilization. Different states adopted the sterilization laws at different paces. These laws, whose constitutionality was upheld by the Supreme Court in their 1927 ruling Buck v. Bell , forced over 60,000 people to go through sterilization in the United States. California's sterilization program
7743-632: Was 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
7832-472: Was so effective that the Nazis turned to the government for advice on how to prevent the birth of the "unfit". While the US eugenics movement lost much of its momentum in the 1940s in view of the horrors of Nazi Germany, advocates of eugenics (including Nazi geneticist Otmar Freiherr von Verschuer ) continued to work and promote their ideas in the United States. In later decades, some eugenic principles have made
7921-498: Was standardized on a sample of 2,200 people in the United States, ranging in age from 16 to 90. 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. The fifth edition of the Wechsler Adult Intelligence Scale
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