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IQ classification is the practice by IQ test publishers of designating IQ score ranges as various categories with labels such as "superior" or "average."[1][2][3] IQ classification was preceded historically by attempts to classify human beings by general ability based on other forms of behavioral observation.[4][5] Those other forms of behavioral observation are still important for validating classifications based on IQ tests. Both intelligence classification by observation of behavior outside the testing room and classification by IQ testing depend on the definition of "intelligence" relevant to a particular case and on the reliability and error of estimation in the classification procedure. All IQ tests show variance in scores even for the same test-taker retested on the same test,[6][7] and also variance in scores for the same test-taker among IQ tests from different publishers.[8] Test publishers have not agreed on uniform designations for IQ score classifications.

Variance in individual IQ classification[edit | edit source]

IQ scores can vary for the same person, so a person does not always belong to the same IQ score range each time the person is tested. (IQ score table data and pupil pseudonyms adapted from description of KABC-II norming study cited in Kaufman 2009.[9])
Asher 90 95 111
Brianna 125 110 105
Colin 100 93 101
Danica 116 127 118
Elpha 93 105 93
Fritz 106 105 105
Georgi 95 100 90
Hector 112 113 103
Imelda 104 96 97
Jose 101 99 86
Keoku 81 78 75
Leo 116 124 102

Individuals can vary in IQ classification from one occasion to another both because numerical IQ scores can vary each time an individual takes a test and because not all test publishers use the same category labels for IQ classification. Both issues must be kept in mind when interpreting an individual's IQ scores.

In general, IQ tests have sufficient reliability that most test-takers age ten or older have similar IQ scores throughout life.[10] But even at that, some individuals score very differently on when taking the same test on different occasions or when taking more than one kind of IQ test.[11] A historical example of individual score variance is the group of young people in the famous longitudinal Genetic Studies of Genius by Lewis Terman (initial n=1,444 with n=643 in main study group). They were first tested at elementary school age after teacher referrals. When they were retested at high school age (n=503), they were found to have dropped 9 IQ points on average in Stanford-Binet IQ. More than two dozen children dropped by 15 IQ points and six by 25 points or more. Parents of those children thought that the children were still as bright as ever, or even brighter.[12]

Because all IQ tests have an error of measurement in the test-taker's IQ score, a test-giver should always inform the test-taker of the confidence interval around the score obtained on a given occasion of taking each test. IQ scores are ordinal scores and are not expressed in an interval measurement unit.[13] Besides the inherent error band around any IQ test score because tests are a "sample of learned behavior,"

IQ scores can also be misleading because test-givers fail to follow standardized administration and scoring procedures. In cases of test-giver mistakes, the usual result is that tests are scored too leniently, while some test-givers err by showing a "halo effect," with low-IQ individuals receiving IQ scores even lower than if standardized procedures were followed, while high-IQ individuals receive inflated IQ scores.[14]

IQ classifications for individuals also vary because category labels for IQ score ranges are specific to each brand of test. The test publishers do not have a uniform practice of labeling IQ score ranges, nor do they have a consistent practice of dividing up IQ score ranges into categories of the same size or with the same boundary scores.[15] Thus psychologists should specify which test was given when reporting a test-taker's IQ.[16] Psychologists and IQ test authors recommend that psychologists adopt the terminology of each test publisher when reporting IQ score ranges.[17][18]

IQ scores have been derived by two different procedures since the invention of IQ tests. The first procedure historically was the "quotient IQ," based on estimating a "mental age" of the test-taker (rounded to a specified number of years and months), which was then divided by the test-taker's chronological age (rounded to a specified number of years and months) and multiplied by 100 so that score numbers would be reported without decimal points.

The current procedure for all IQ tests is the "deviation IQ," in which an IQ score of 100 means performance on the test item content like the median level of performance in the test's sample size, an IQ score of 115 means performance one standard deviation above the median, a score of 85 performance one standard deviation below the median, and so on.[19] Lewis Terman and other early developers of IQ tests noticed that child IQ scores come out to approximately the same number by either procedure. Deviation IQs are now used for standard scoring of all IQ tests in large part because they allow a consistent definition of IQ for both children and adults. By the current definition of IQ test standard scores, about two-thirds of all test-takers obtain scores from 85 to 115, and about 5 percent of the population scores above 125.[20]


Score Distribution Chart for Sample of 905 Children Tested on 1916 Stanford-Binet Test

IQ classifications from IQ testing are not the last word on how a test-taker will do in life, nor are they the only information to be considered for placement in school or job-training programs. There is still a dearth of information about how behavior differs between persons with differing IQ scores.[21] For placement in school programs, for medical diagnosis, and for career advising, factors other than IQ must also be part of an individual assessment.

The lesson here is that classification systems are necessarily arbitrary and change at the whim of test authors, government bodies, or professional organizations. They are statistical concepts and do not correspond in any real sense to the specific capabilities of any particular person with a given IQ. The classification systems provide descriptive labels that may be useful for communication purposes in a case report or conference, and nothing more.[22]

—Alan S. Kaufman and Elizabeth O. Lichtengerger, Assessing Adolescent and Adult Intelligence (2006)

IQ classification on current tests[edit | edit source]

There are a variety of individually administered IQ tests in use in the English-speaking world.[23][24] Not all report test results as "IQ," but most now report a standard score with a median score level of 100. When a test-taker scores higher or lower than the median score, the score is indicated as 15 standard score points higher or lower for each standard deviation difference higher or lower in the test-taker's performance on the test item content.

Wechsler Intelligence Scales[edit | edit source]

Main article: Wechsler Adult Intelligence Scale

The Wechsler intelligence scales were originally developed from earlier intelligence scales by David Wechsler. The first Wechsler test published was the Wechsler-Bellevue Scale in 1939.[25] The Wechsler IQ tests for children and for adults are the most frequently used individual IQ tests in the English-speaking world[26] and in their translated versions are perhaps the most widely used IQ tests worldwide.[27] The Wechsler tests have long been regarded as the "gold standard" in IQ testing.[28] The Wechsler Adult Intelligence Scale—Fourth Edition (WAIS–IV) was published in 2008 by Psychological Corporation.[23] The Wechsler Intelligence Scale for Children—Fourth Edition (WISC–IV) was published in 2003 by Psychological Corporation, and the Wechsler Preschool and Primary Scale of Intelligence—Fourth Edition (WPPSI–IV) was published in 2012 by Psychological Corporation. Like all current IQ tests, the Wechsler tests report a "deviation IQ" as the standard score for the full-scale IQ, with the norming sample median raw score defined as IQ 100 and a score one standard deviation higher defined as IQ 115 (and one deviation lower defined as IQ 85).

Current Wechsler (WAIS–IV, WISC–IV, WPPSI–IV) IQ classification
IQ Range ("deviation IQ") IQ Classification
130 and above Very Superior
120–129 Superior
110–119 High Average
90–109 Average
80–89 Low Average
70–79 Borderline
69 and below Extremely Low

Psychologists have proposed alternative language for Wechsler IQ classifications.[29][30] Note especially that the term "borderline," which implies being very close to being intellectually disabled, is replaced in the alternative system by a term that doesn't imply a medical diagnosis.

Alternate Wechsler IQ Classifications (after Groth-Marnat 2009)[31]
Corresponding IQ Range Classifications More value-neutral terms
130+ Very superior Upper extreme
120–129 Superior Well above average
110–119 High average High average
90–109 Average Average
80–89 Low average Low average
70–79 Borderline Well below average
69 and below Extremely low Lower extreme

Stanford-Binet Intelligence Scale Fifth Edition[edit | edit source]

Main article: Stanford-Binet Intelligence Scales

The current fifth edition of the Stanford-Binet scales (SB5) was developed by Gale H. Roid and published in 2003 by Riverside Publishing.[23] Unlike scoring on previous versions of the Stanford-Binet test, SB5 IQ scoring is deviation scoring in which each standard deviation up or down from the norming sample median score is 15 points from the median score, IQ 100, just like the standard scoring on the Wechsler tests.

Stanford-Binet Fifth Edition (SB5) classification[32]
IQ Range ("deviation IQ") IQ Classification
145–160 Very gifted or highly advanced
130–144 Gifted or very advanced
120–129 Superior
110–119 High average
90–109 Average
80–89 Low average
70–79 Borderline impaired or delayed
55–69 Mildly impaired or delayed
40–54 Moderately impaired or delayed

Woodcock-Johnson Test of Cognitive Abilities[edit | edit source]

Main article: Woodcock–Johnson Tests of Cognitive Abilities

The Woodcock-Johnson III NU Tests of Cognitive Abilities (WJ III NU) was developed by Richard W. Woodcock, Kevin S. McGrew and Nancy Mather and published in 2007 by Riverside.[23] Note that the WJ III classification terms are not applied to the same score ranges as for the Wechsler or Stanford-Binet tests.

Woodcock-Johnson R
IQ Score WJ III Classification[33]
131 and above Very superior
121 to 130 Superior
111 to 120 High Average
90 to 110 Average
80 to 89 Low Average
70 to 79 Low
69 and below Very Low

Kaufman Tests[edit | edit source]

The Kaufman Adolescent and Adult Intelligence Test was developed by Alan S. Kaufman and Nadeen L. Kaufman and published in 1993 by American Guidance Service.[23] Kaufman test scores "are classified in a symmetrical, nonevaluative fashion,"[34] in other words the score ranges for classification are just as wide above the median as below the median, and the classification labels do not purport to assess individuals.

KAIT 1993 IQ classification
130 and above Upper Extreme
120–129 Well Above Average
110–119 Above average
90–109 Average
80–89 Below Average
70–79 Well Below Average
69 and below Lower Extreme
Main article: Kaufman Assessment Battery for Children

The Kaufman Assessment Battery for Children, Second Edition was developed by Alan S. Kaufman and Nadeen L. Kaufman and published in 2004 by American Guidance Service.[23]

KABC-II 2004 Descriptive Categories[35][36]
Range of Standard Scores Name of Category
131–160 Upper Extreme
116–130 Above Average
85–115 Average Range
70–84 Below Average
40–69 Lower Extreme

Cognitive Assessment System[edit | edit source]

Main article: Cognitive Assessment System

The Das-Naglieri Cognitive Assessment System test was developed by Jack Naglieri and J. P. Das and published in 1997 by Riverside.[23]

Cognitive Assessment System 1997 full scale score classification[37]
Standard Scores Classification
130 and above Very Superior
120–129 Superior
110–119 High Average
90–109 Average
80–89 Low Average
70–79 Below Average
69 and below Well Below Average

Differential Ability Scales[edit | edit source]

Main article: Differential Ability Scales

The Differential Ability Scales Second Edition (DAS–II) was developed by Colin D. Elliott and published in 2007 by Psychological Corporation.[23] The DAS-II is a test battery given individually to children, normed for children from ages two years and six months through seventeen years and eleven months.[38] It was normed on 3,480 noninstitutionalized, English-speaking children in that age range.[39] The DAS-II yields a General Conceptual Ability (GCA) score scaled like an IQ score with the median standard score set at 100 and 15 standard score points for each standard deviation up or down from the median. The lowest possible GCA on the is DAS–II is 44, and the highest is 175.[40]

DAS-II 2007 GCA classification[41]
GCA General Conceptual Ability Classification
≥ 130 Very high
120–129 High
110–119 Above average
90–109 Average
80–89 Below average
70–79 Low
≤ 69 Very low

Reynolds Intellectual Ability Scales[edit | edit source]

Reynolds Intellectual Ability Scales (RIAS) were developed by Cecil Reynolds and Randy Kamphaus. The RIAS was published in 2003 by Psychological Assessment Resources.[23]

RIAS 2003 Scheme of Verbal Descriptors of Intelligence Test Performance[42]
Intelligence test score range Verbal descriptor
≥ 130 Significantly above average
120–129 Moderately above average
110–119 Above average
90–109 Average
80–89 Below average
70–79 Moderately below average
≤ 69 Significantly below average

Historical IQ classification labels[edit | edit source]

Lewis Terman, developer of the Stanford-Binet Intelligence Scales, based his English-language Stanford-Binet Intelligence Scales on the French-language Binet-Simon test developed by Alfred Binet. Terman believed his test measured the "general intelligence" construct advocated by Charles Spearman (1904).[43] Terman differed from Binet in reporting scores on his test in the form of intelligence quotient ("mental age" divided by chronological age) scores after the 1912 suggestion of German psychologist William Stern. Terman chose the category names for score levels on the Stanford-Binet test. When he first chose classification for score levels, he relied partly on the usage of earlier authors who wrote, before the existence of IQ tests, on topics such as individuals unable to care for themselves in independent adult life. Terman's first version of the Stanford-Binet was based on norming samples that included only white, American-born subjects, mostly from California, Nevada, and Oregon.[44]

Terman's Stanford-Binet original (1916) classification[45][46]
IQ Range ("ratio IQ") IQ Classification
Above 140 "Near" genius or genius
120–140 Very superior intelligence
110–120 Superior intelligence
90–110 Normal, or average, intelligence
80–90 Dullness, rarely classifiable as feeble-mindedness
80–90 Border-line deficiency, sometimes classifiable as dullness, often as feeble-mindedness
Below 70 Definite feeble-mindedness

Rudolph Pintner proposed a set of classification terms in his 1923 book Intelligence Testing: Methods and Results.[3] Pintner commented that psychologists of his era, including Terman, went about "the measurement of an individual's general ability without waiting for an adequate psychological definition."[47] Pintner retained these terms in the 1931 second edition of his book.[48]

Pintner 1923 IQ classification[3]
IQ Range ("ratio IQ") IQ Classification
130 and above Very Superior
120–129 Very Bright
110–119 Bright
90–109 Normal
80–89 Backward
70–79 Borderline

Albert Julius Levine and Louis Marks proposed a broader set of categories in their 1928 book Testing Intelligence and Achievement.[49] Some of the terminology in the table came from contemporary terms for classifying individuals with intellectual disabilities.

Levine and Marks 1928 IQ classification[49]
IQ Range ("ratio IQ") IQ Classification
175 of above Precocious
150–174 Very superior
125–149 Superior
115–124 Very bright
105–114 Bright
95–104 Average
85–94 Dull
75–84 Borderline
50–74 Morons
25–49 Imbeciles
0–24 Idiots

The second revision (1937) of the Stanford-Binet test retained "quotient IQ" scoring, despite earlier criticism of that method of reporting IQ test standard scores.[50] The term "genius" was no longer used for any IQ score range.[51] The second revision was normed only on children and adolescents (no adults), and only "American-born white children."[52]

Terman's Stanford-Binet Second Revision (1937) classification[51]
IQ Range ("ratio IQ") IQ Classification
140 and over Very superior
120–139 Superior
110–119 High average
90–109 Normal or average
80–89 Low average
70–79 Borderline defective
Below 60 Mentally defective

A data table published later as part of the manual for the 1960 Third Revision (Form L-M) of the Stanford-Binet test reported score distributions from the 1937 second revision standardization group.

Score Distribution of Stanford-Binet 1937 Standardization Group[51]
IQ Range ("ratio IQ") Percent of Group
160–169 0.03
150–159 0.2
140–149 1.1
130–139 3.1
120–129 8.2
110–119 18.1
100–109 23.5
90–99 23.0
80–89 14.5
70–79 5.6
60–69 2.0
50–59 0.4
40–49 0.2
30–39 0.03

David Wechsler, developer of the Wechsler-Bellevue Scale of 1939 (which was later developed into the Wechsler Adult Intelligence Scale) popularized the use of "deviation IQs" as standard scores of IQ tests rather than the "quotient IQs" ("mental age" divided by "chronological age") then used for the Stanford-Binet test.[53] He devoted a whole chapter in his book The Measurement of Adult Intelligence to the topic of IQ classification and proposed different category names from those used by Lewis Terman. Wechsler also criticized the practice of earlier authors who published IQ classification tables without specifying which IQ test was used to obtain the scores reported in the tables.[54]

Wechsler-Bellevue 1939 IQ classification
IQ Range ("deviation IQ") IQ Classification Percent Included
128 and over Very Superior 2.2
120–127 Superior 6.7
111–119 Bright Normal 16.1
91–110 Average 50.0
80–90 Dull normal 16.1
66–89 Borderline 6.7
65 and below Defective 2.2

In 1958, Wechsler published another edition of his book Measurement and Appraisal of Adult Intelligence. He revised his chapter on the topic of IQ classification and commented that "mental age" scores were not a more valid way to score intelligence tests than IQ scores.[55] He continued to use the same classification terms.

Wechsler Adult Intelligence Scales 1958 Classification[56]
IQ Range ("deviation IQ") IQ Classification Percent Included
128 and over Very Superior 2.2
120–127 Superior 6.7
111–119 Bright Normal 16.1
91–110 Average 50.0
80–90 Dull normal 16.1
66–89 Borderline 6.7
65 and below Defective 2.2

The third revision (Form L-M) in 1960 of the Stanford-Binet IQ test used the deviation scoring pioneered by David Wechsler. For rough comparability of scores between the second and third revision of the Stanford-Binet test, scoring table author Samuel Pinneau set 100 for the median standard score level and 16 standard score points for each standard deviation above or below that level. The highest score obtainable by direct look-up from the standard scoring tables (based on norms from the 1930s) was IQ 171 at various chronological ages from three years six months (with a test raw score "mental age" of six years and two months) up to age six years and three months (with a test raw score "mental age" of ten years and three months).[57] The classification for Stanford-Binet L-M scores does not include terms such as “exceptionally gifted” and “profoundly gifted” in the test manual itself.

Terman's Stanford-Binet Third Revision (Form L-M) classification[32]
IQ Range ("deviation IQ") IQ Classification
140 and over Very superior
120–139 Superior
110–119 High average
90–109 Normal or average
80–89 Low average
70–79 Borderline defective
Below 60 Mentally defective

The first edition of the Woodcock-Johnson Tests of Cognitive Abilities was published by Riverside in 1977. The classifications used by the WJ-R Cog were "modern in that they describe levels of performance as opposed to offering a diagnosis."[33]

Woodcock-Johnson R
IQ Score WJ-R Cog 1977 Classification[33]
131 and above Very superior
121 to 130 Superior
111 to 120 High Average
90 to 110 Average
80 to 89 Low Average
70 to 79 Low
69 and below Very Low

The fourth revision of the Stanford-Binet scales (S-B IV) was developed by Thorndike, Hagen, and Sattler and published by Riverside Publishing in 1986. It retained the deviation scoring of the third revision with each standard deviation from the median being defined as a 16 IQ point difference. The S-B IV adopted new classification terminology. After this test was published, psychologist Nathan Brody lamented that IQ tests had still not caught up with advances in research on human intelligence during the twentieth century.[58]

Stanford-Binet Intelligence Scale, Fourth Edition (S-B IV) 1986 classification[59][60]
IQ Range ("deviation IQ") IQ Classification
132 and above Very superior
121–131 Superior
111–120 High average
89–110 Average
79–88 Low average
68–78 Slow learner
67 or below Mentally retarded

The third edition of the Wechsler Adult Intelligence Scale (WAIS-III) used different classification terminology from the earliest versions of Wechsler tests.

Wechsler (WAIS–III) 1997 IQ test classification
IQ Range ("deviation IQ") IQ Classification
130 and above Very superior
120–129 Superior
110–119 High average
90–109 Average
80–89 Low average
70–79 Borderline
69 and below Extremely low

Classification of low-IQ individuals[edit | edit source]

Main article: Intellectual disability
Mental retardation
Classification and external resources
ICD-10 F70-F79
ICD-9 317-319
DiseasesDB 4509
MedlinePlus 001523
eMedicine med/3095 neuro/605
MeSH D008607

The earliest terms for classifying individuals of low intelligence were medical or legal terms that preceded the development of IQ testing.[4][5] The legal system recognized a concept of some individuals being so cognitively impaired that they were not responsible for criminal behavior. Medical doctors sometimes encountered adult patients who could not live independently, being unable to take care of their own daily living needs. Various terms were used to attempt to classify individuals with varying degrees of intellectual disability. Many of the earliest terms are now considered very offensive.

In current medical diagnosis, IQ scores alone are not conclusive for a finding of intellectual disability. Recently adopted diagnostic standards place the major emphasis on adaptive behavior of each individual, with IQ score just being one factor in diagnosis in addition to adaptive behavior scales, and no category of intellectual disability being defined primarily by IQ scores.[61] Psychologists point out that evidence from IQ testing should always be used with other assessment evidence in mind: "In the end, any and all interpretations of test performance gain diagnostic meaning when they are corroborated by other data sources and when they are empirically or logically related to the area or areas of difficulty specified in the referral."[62]

In the United States, a holding by the Supreme Court in the case Atkins v. Virginia, 536 U.S. 304 (2002) bars states from imposing capital punishment on persons with mental retardation, defined in subsequent cases as persons with IQ scores below 70. This legal standard continues to be actively litigated in capital cases.[63]

Classification of high-IQ individuals[edit | edit source]

IQ classification and genius[edit | edit source]

Main article: Genius

Francis Galton (1822–1911) was a pioneer in investigating both eminent human achievement and mental testing. In his book Hereditary Genius, writing before the development of IQ testing, he proposed that hereditary influences on eminent achievement are strong, and that eminence is rare in the general population. Lewis Terman chose "'near' genius or genius" as the classification label for the highest classification on his 1916 version of the Stanford-Binet test.[45] By 1926, Terman began publishing about a longitudinal study of California schoolchildren who were referred for IQ testing by their schoolteachers, called Genetic Studies of Genius, which he conducted for the rest of his life. Catherine M. Cox, a colleague of Terman's, wrote a whole book, The Early Mental Traits of 300 Geniuses, published as volume 2 of The Genetic Studies of Genius book series, in which she analyzed biographical data about historic geniuses. Although her estimates of childhood IQ scores of historical figures who never took IQ tests have been criticized on methodological grounds,[64][65][66] Cox's study was thorough in finding out what else matters besides IQ in becoming a genius.[67] By the 1937 second revision of the Stanford-Binet test, Terman no longer used the term "genius" as an IQ classification, nor has any subsequent IQ test.[51][68] In 1939, Wechsler specifically commented that "we are rather hesitant about calling a person a genius on the basis of a single intelligence test score."[69]

The Terman longitudinal study in California eventually provided historical evidence on how genius is related to IQ scores.[70] Many California pupils were recommended for the study by schoolteachers. Two pupils who were tested but rejected for inclusion in the study because of IQ scores too low for the study grew up to be Nobel Prize winners in physics, William Shockley,[71][72] and Luis Walter Alvarez.[73][74] Based on the historical findings of the Terman study and on biographical examples such as Richard Feynman, who had an IQ of 125 and went on to win the Nobel Prize in physics and become widely known as a genius,[75][76] the current view of psychologists and other scholars of genius is that a minimum level of IQ, no higher than about IQ 125, is strictly necessary for genius, but that level of IQ is also sufficient for development of genius only when combined with the other influences on individual development of genius identified by Cox's biographical study, namely opportunity for talent development and personality characteristics of drive and persistence.[77][78][79]

IQ classification and giftedness[edit | edit source]

Main article: Intellectual giftedness

A major point of consensus among all scholars of intellectual giftedness is that there is no generally agreed definition of giftedness.[80] Although there is no scholarly agreement about identifying gifted learners, there is a de-facto reliance on IQ scores for identifying participants in school gifted education programs. Most school districts consider children in the upper 2-3% of the IQ distribution, approximately IQ 130+, to be mentally gifted.[81]

As long ago as 1937, Lewis Terman pointed out that error of estimation in IQ scoring increases as IQ score increases, so that there is less and less certainty about assigning a test-taker to one band of scores or another as one looks at higher bands.[82] Current IQ tests also have large error bands for high IQ scores.[83] As an underlying reality, such distinctions as those between “exceptionally gifted” and “profoundly gifted” have never been well established. All longitudinal studies of IQ have shown that test-takers can bounce up and down in score, and thus switch up and down in rank order as compared to one another, over the course of childhood. Some test-givers claim that IQ classification categories such as "profoundly gifted" are meaningful, but those are based on the obsolete Stanford-Binet Third Revision (Form L-M) test.[84] Moreover there has never, ever been any validation of the Stanford-Binet L-M on adult populations, and there is no trace of such terminology in the writings of Lewis Terman. Although two current tests attempt to provide "extended norms" that allow for classification of different levels of giftedness, those norms are not based on well validated data.[85]

See also[edit | edit source]

References[edit | edit source]

  1. Wechsler 1958, Chapter 3: The Classification of Intelligence
  2. Matarazzo 1972, Chapter 5: The Classification of Intelligence
  3. 3.0 3.1 3.2 Kamphaus 2005
  4. 4.0 4.1 Terman 1916
  5. 5.0 5.1 Wechsler 1939
  6. Aiken 1979
  7. Anastasi & Urbina 1997
  8. Kaufman 2009
  9. Kaufman 2009, Figure 5.1 IQs earned by preadolescents (ages 12–13) who were given three different IQ tests in the early 2000s
  10. Mackintosh 2001
  11. Uzieblo et al. Magez
  12. Shurkin 1992
  13. Matarazzo 1972 Gottfredson 2009 Mackintosh 2011 Flynn 2012
  14. Kaufman & Lichtenberger 2006
  15. Reynolds & Horton 2012, Table 4.1 Descriptions for Standard Score Performances Across Selected Pediatric Neuropsychology Tests
  16. Aiken 1979
  17. Sattler 1988
  18. Sattler 2001
  19. Gottfredson 2009
  20. Hunt 2011
  21. Gottfredson 2009
  22. Kaufman & Lichtenberger 2006
  23. 23.0 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 Urbina 2011, Table 2.1 Major Examples of Current Intelligence Tests
  24. Flanagan & Harrison 2012, chapters 8-13, 15-16 (discussing Wechsler, Stanford-Binet, Kaufman, Woodcock-Johnson, DAS, CAS, and RIAS tests)
  25. Mackintosh & 2011 page 32 "The most widely used individual IQ tests today are the Wechsler tests, first published in 1939 as the Wechsler-Bellevue Scale."
  26. Saklofske et al. 2003
  27. Georgas et al. 2003
  28. Meyer & Weaver 2005 Campbell 2006 Strauss 2006 Foote 2007 Kaufman & Lichtenberger 2006 Hunt 2011
  29. Kamphaus 2005
  30. Groth-Marnat 2009
  31. Groth-Marnat 2009, Table 5.5
  32. 32.0 32.1 Kaufman 2009
  33. 33.0 33.1 33.2 Kamphaus 2005
  34. Kamphaus 2005
  35. Kaufman et al. 2005, Table 3.1 Descriptive Category System
  36. Gallagher & Sullivan 2011
  37. Naglieri 1999, Table 4.1 Descriptive Categories of PASS and Full Scale Standard Scores
  38. Dumont, Willis & Elliot 2009
  39. Dumont, Willis & Elliot 2009
  40. Dumont & Willis 2013, "Range of DAS Subtest Scaled Scores" (Web resource) "The range of DAS GCA is 44 to 175. This range is not available at some ages. For example, the highest possible GCA that adolescents who are aged 17 years 11 months can get is 156; the lowest possible GCA that children who are 2 years 6 month old can get is 53."
  41. Dumont, Willis & Elliot 2009, Table Rapid Reference 5.1 DAS-II Classification Schema
  42. Reynolds & Kamphaus n.d.
  43. Wasserman 2012
  44. Wasserman 2012
  45. 45.0 45.1 Terman 1916
  46. Kaufman 2009
  47. Naglieri 1999
  48. Pintner 1931
  49. 49.0 49.1 Wasserman et al. 2012
  50. Wasserman 2012
  51. 51.0 51.1 51.2 51.3 Terman 1960
  52. Terman & Merrill 1937
  53. Wasserman 2012
  54. Wechsler 1939
  55. Wechsler 1958
  56. Wechsler 1958
  57. Terman & Merrill 1960
  58. Naglieri 1999
  59. Sattler 1988, Table BC-2 Classification Ratings on Stanford-Binet: Fourth Edition, Wechsler Scales, and McCarthy Scales
  60. Kaufman 2009
  61. American Psychiatric Association 2013
  62. Flanagan & Kaufman 2009
  63. Flynn 2012, Chapter 4: Death, Memory, and Politics
  64. Pintner 1931
  65. Shurkin 1992
  66. Eysenck 1998
  67. Cox 1926
  68. Kaufman 2009
  69. Wechsler 1939
  70. Eysenck 1998
  71. Simonton 1999
  72. Shurkin 2006
  73. Leslie 2000, "We also know that two children who were tested but didn't make the cut -- William Shockley and Luis Alvarez -- went on to win the Nobel Prize in Physics. According to Hastorf, none of the Terman kids ever won a Nobel or Pulitzer."
  74. Park, Lubinski & Benbow 2010, "There were two young boys, Luis Alvarez and William Shockley, who were among the many who took Terman’s tests but missed the cutoff score. Despite their exclusion from a study of young 'geniuses,' both went on to study physics, earn PhDs, and win the Nobel prize."
  75. Gleick 2011
  76. Robinson 2011
  77. Jensen 1998
  78. Eysenck 1998
  79. Cf. Pickover 1998
  80. Sternberg, Jarvin & Grigorenko 2010, Chapter 2: Theories of Giftedness
  81. Weiten, Wayne (2011). Psychology: Themes and Variations, Ninth, Cengage Learning.
  82. Terman & Merrill 1937
  83. Lohman & Foley Nicpon 2012, Section "Conditional SEMs" "The concerns associated with SEMs [standard errors of measurement] are actually substantially worse for scores at the extremes of the distribution, especially when scores approach the maximum possible on a test . . . when students answer most of the items correctly. In these cases, errors of measurement for scale scores will increase substantially at the extremes of the distribution. Commonly the SEM is from two to four times larger for very high scores than for scores near the mean (Lord, 1980)."
  84. Lohman & Foley Nicpon 2012, Section "Scaling Issues" "The spreading out of scores for young children at the extremes of the ratio IQ scale is viewed as a positive attribute of the SB-LM by clinicians who want to distinguish among the highly and profoundly gifted (Silverman, 2009). Although spreading out the test scores in this way may be helpful, the corresponding normative scores (i.e., IQs) cannot be trusted both because they are based on out-of-date norms and because the spread of IQ scores is a necessary consequence of the way ratio IQs are constructed, not a fact of nature."
  85. Lohman & Foley Nicpon 2012, Section "Scaling Issues" "Modern tests do not produce such high scores, in spite of heroic efforts to provide extended norms for both the Stanford Binet, Fifth Edition (SB-5) and the WISC-IV (Roid, 2003; Zhu, Clayton, Weiss, & Gabel, 2008)."

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