False Assumption Registry

Flynn Effect Shows Real IQ Gains

False Assumption: Mean IQ scores rose substantially during the 20th century due to a genuine increase in the capacity for intelligence.

Summaries Written by FARAgent (AI) on February 16, 2026 · Pending Verification

For much of the late 20th century, the Flynn effect looked like a plain fact with an obvious meaning: IQ scores kept rising, sometimes by roughly 3 points a decade, so people must be getting smarter. That was not a foolish inference. The gains appeared across countries and across decades, and they arrived alongside real improvements in health, schooling, nutrition, family size, and the cognitive demands of modern life. If raw scores climbed by 30 points or more from the 1920s onward, a reasonable observer could conclude that modern societies were producing a genuine increase in intellectual capacity, not just better test-taking.

The trouble began when researchers looked more closely at what was rising. The biggest gains often showed up on abstract, culture-loaded, or test-specific items, not in the broad, stable general intelligence, g, that many psychologists treated as the thing IQ tests were supposed to capture. Arthur Jensen and others warned early that large score gains over time sat awkwardly beside the stubborn rank order of individuals and groups, and beside the fact that nobody believed the average person in 1990 was a genius by 1930 standards. Later work found mixed patterns: gains that varied by subtest, country, and period, reversals in some places, and evidence that environmental improvements can raise scores without clearly raising the underlying trait in the old, simple sense.

So the old slogan, rising IQ means rising intelligence, no longer carries the easy confidence it once did. A substantial body of experts now rejects the strong version of that claim, arguing that the Flynn effect shows changes in test performance more than a clean, across-the-board increase in general cognitive ability. Others still hold that at least part of the gain is real, pointing to better nutrition, reduced disease burden, schooling, and even secular increases in brain size as signs that something substantive improved. The debate now is less about whether scores rose, they did, than about what exactly rose with them.

Status: A significant portion of experts think this assumption was false
People Involved
  • James Flynn was a political scientist at the University of Otago who in 1984 published the paper that gave the phenomenon its name. He combed through old test manuals and standardization samples from the United States and found that Americans born later scored about 13.8 points higher on earlier versions of the same tests, roughly three points per decade. Flynn presented the data plainly and insisted the gains were real, though he grew increasingly skeptical they reflected genuine rises in intelligence itself. His later writings and 2013 TED Talk framed the effect as evidence of shifting habits of mind rather than raw cognitive capacity. The term Flynn effect entered textbooks and policy debates largely because of his persistence. [2][5][11]
  • Arthur Jensen was a psychologist at the University of California who spent decades defending the concept of g, the general factor of intelligence. He viewed the reported gains with deep suspicion and laid out strict criteria that any legitimate secular trend must satisfy: comprehensive samples, unaltered tests, mature participants, and culture-reduced instruments. Jensen repeatedly warned that the apparent rises looked more like test sophistication than increases in g. His cautions were cited by Flynn himself as the proper framework for evaluation, yet they were often sidelined in the rush to celebrate rising scores. [3][6]
  • Richard Herrnstein and Charles Murray, authors of the 1994 book The Bell Curve, acknowledged the Flynn effect while advancing their argument that high heritability of IQ would sort society into cognitive classes. They coined the very term Flynn effect in their pages and treated the score increases as a rise in test performance rather than a direct contradiction of their meritocracy thesis. The book brought the phenomenon to a wide audience of policymakers and journalists who had never read the original papers. [5][11]
▶ Supporting Quotes (27)
“Named the Flynn effect after intelligence researcher James Flynn, this secular increase in mean IQ has been much debated.”— How real was the Flynn effect?
“Through personal communications, Arthur Jensen expressed four reservations: (a) The possibility of sample bias should be eliminated by comprehensive samples, such as mass testing of draft registrants; (b) tests should remain unaltered from one generation to another, and estimates of trends should be based on raw score differences; (c) particular emphasis should be placed on using mature participants, participants who have reached the peak of their raw score performance; (d) particular emphasis should be placed on culture-reduced tests like Raven's Progressive Matrices.”— Searching for Justice: The Discovery of IQ Gains Over Time
“The discovery of IQ gains over time emerged naturally from the work of many scholars... Charles Murray called IQ gains the "Flynn effect" because I inferred that they were part of a persistent and perhaps universal phenomenon.”— Searching for Justice: The Discovery of IQ Gains Over Time
“Charles Murray called IQ gains the "Flynn effect" because I inferred that they were part of a persistent and perhaps universal phenomenon (Herrnstein & Murray, 1994, p. 307).”— Searching for Justice: The Discovery of IQ Gains Over Time
“A dialogue with Arthur Jensen and Charles Murray, thinkers equally committed to social justice, was almost inevitable.”— Searching for Justice: The Discovery of IQ Gains Over Time
“The term 'Flynn Effect' derives from James Flynn's article in the Psychological Bulletin (Flynn, 1984) on 'massive gains' in the mean IQ of Americans from 1932 to 1978. Flynn (1987) followed it with a similar review of ‘massive IQ gains’ in 14 nations. Then, in the American Psychologist, Flynn (1999) discussed the educational and social implications of secular gains in IQ.”— The theory of intelligence and its measurement
“Three new books cite the Flynn Effect and the secular rise in IQ in support of the cultural perspective: Richard Nisbett 2009 Intelligence and How to Get It ... In a technical Appendix, “The Case for a Purely Environmental Basis for Black/White Differences in IQ,” Nisbett submitted nine categories of empirical evidence to argue against race-IQ differences being heritable.”— The theory of intelligence and its measurement
“However, in The g Factor and elsewhere, Jensen has long pointed out that increased test sophistication and other factors lead to enhanced test taking skills and higher scores and that it is important to disentangle IQ test gains from psychometric g gains. He predicted no significant real-world effects in terms of intelligence.”— The theory of intelligence and its measurement
“In 1984, James Flynn found that American standardization samples, including children, scored systematically higher on older versions of IQ tests than they did on newer versions.”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“The Flynn effect is named for James Robert Flynn, who did much to document it and promote awareness of its implications.”— Flynn effect - Wikipedia
“The term “Flynn Effect” was created by Herrnstein and Murray in 1994 to refer to James Flynn’s findings of this increase in IQ over time (Williams, 2013; Herrnstein & Murray, 2010).”— Flynn effect - Wikipedia
“Flynn stated that, if asked, he would have named the effect after Read D. Tuddenham who 'was the first to present convincing evidence of massive gains on mental tests using a nationwide sample' in a 1948 article.”— Flynn effect - Wikipedia
“Ulric Neisser estimated that using the IQ values of 1997, the average IQ of the United States in 1932, according to the first Stanford–Binet Intelligence Scales standardization sample, was 80.”— Flynn effect - Wikipedia
“James R. Flynn Department of Political Studies University of Otago, Dunedin, New Zealand”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“four general criteria derived from suggestions made by A. R. Jensen (personal communications, January 12 and February 3, 1983)”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“documented by Flynn (1984a) in a study on intelligence quotient (IQ) score gains in the standardization samples of successive versions of Stanford-Binet and Wechsler intelligence tests.”— The Flynn Effect: A Meta-analysis
“Kanaya, Ceci, and Scullin (2003a) and Kanaya, Scullin, and Ceci (2003b) documented a pattern of “rising and falling” IQ scores in children diagnosed with an intellectual disability or learning disability as a function of the release date of the new version of an intelligence test.”— The Flynn Effect: A Meta-analysis
“Austria: Pietschnig and Gittler 2015”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“Flynn (1984) documen- ted the trend in U.S. IQ data and then showed its existence in 14 developed countries (Flynn, 1987).”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“Rodgers (1998), in a general critique of research on the Flynn Effect, suggested that “research addressing the legitimacy and meaning of the effect should precede research testing for and evaluating causes of the effect” (p. 338, italics in original).”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“documented by Flynn (1984a) in a study on intelligence quotient (IQ) score gains in the standardization samples of successive versions of Stanford-Binet and Wechsler intelligence tests. Flynn’s study revealed a 13.8-point increase in IQ scores between 1932 and 1978, amounting to a 0.3-point increase per year, or approximately 3 points per decade. More recently, the Flynn effect was supported by calculations of IQ score gains between 1972 and 2006 for different normative versions of the Stanford-Binet (SB), Wechsler Adult Intelligence Scale (WAIS), and Wechsler Intelligence Scale for Children (WISC) (Flynn, 2009a).”— The Flynn Effect: A Meta-analysis
“The Flynn Effect refers to the finding that the average human IQ has increased over time, first discovered by researcher James Flynn in 1984.”— What Is The Flynn Effect In Psychology?
“One such review by Rodgers (1998) argues that “the acceptance of the effect has been too quick” and that “before the effect is taken seriously by the community of social science researchers, its very existence should not be questionable” (Rodgers, 1998).”— What Is The Flynn Effect In Psychology?
“An exemplary study that showed a positive Flynn effect is Ang, Rodgers and Wänström’s one in which they used the Children of the National Longitudinal Survey of Youth (CNLSY) cohort to showcase the Flynn effect in the PIAT Mathematics test.”— The Other Type of Flynn Effect
“It’s named after the political scientist James Flynn, who has written about it most extensively.”— Intelligence: All That Matters
“some of the early researchers, like Galton, would likely have been appalled to see the end results of the eugenics movement.”— Intelligence: All That Matters
“recall that the first tests were designed by Binet in order to help, not eliminate, children with extra difficulties in education.”— Intelligence: All That Matters
Organizations Involved

The American Psychological Association published Flynn’s seminal 1984 article in its flagship journal American Psychologist and thereby lent institutional weight to the idea that mean IQ scores were climbing. The APA’s platform turned an obscure finding into the standard citation for anyone arguing that environment could dramatically reshape cognitive scores. Later APA task forces on intelligence cited the gains as important context while stopping short of declaring them proof of rising intelligence. [2]

The Dutch military authorities tested nearly every 18-year-old male conscript with the same unaltered 40-item Raven’s Progressive Matrices from 1945 onward. Their records supplied some of the cleanest data on generational change, showing roughly 20 raw-score points gained in thirty years. Similar comprehensive testing programs in Belgium and Norway fed the international literature and made the Flynn effect appear robust across borders. [6]

The American Association on Intellectual and Developmental Disabilities maintained an IQ cutoff of 70 for the legal definition of intellectual disability. In practice many clinicians and courts applied old norms without adjustment, producing abrupt swings in eligibility when new tests appeared. The organization’s guidelines mentioned clinical judgment but rarely emphasized the need to correct for secular gains. [7]

▶ Supporting Quotes (9)
“January 1999 • American Psychologist Copyright 1999 by the American Psychological Association, Inc.”— Searching for Justice: The Discovery of IQ Gains Over Time
“The Dutch military examines virtually all 18-year-old men... In 1945, the military selected 40 of the most discriminating items of the 60 in the Ravens Progressive Matrices Test, and that test has remained unaltered to the present.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“The Belgian military examines all 18-year-old men except those deferred to continue with their edu-”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“The organization accepts scores from a variety of tests, often with no specification of which version of the test. The Stanford-Binet IV and Stanford-Binet 5 are both permitted.”— The Flynn Effect: A Meta-analysis
“The identification of an intellectual disability in the United States requires the presence of significant limitations in intellectual functioning and adaptive behavior prior to age 18 (American Association on Intellectual and Developmental Disabilities [AAIDD], 2010). Although the gold standard AAIDD criteria stress the importance of exercising clinical judgment in the interpretation of IQ scores (e.g., accounting for measurement error), a cut-off score of 70 commonly is used to indicate a significant limitation in intellectual functioning.”— The Flynn Effect: A Meta-analysis
“This study accessed standardization samples of the Intelligence Base Functions (IBFs) from the database of a well-established Austrian test publisher.”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“The National Longitudinal Survey of Youth (NLSY) began as a household probability sample of 12,686 adolescents aged 14–21 at the end of 1978.”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“None of the peer reviewers or editors at Intelligence or any other journal publishing similar analyses noticed the problem either.”— The Other Type of Flynn Effect
“in 2014, the US Supreme Court ruled a rigid cut-off score of 70 unconstitutional.”— Intelligence: All That Matters
The Foundation

The strongest case for the assumption rested on decades of consistent data. Successive versions of the same IQ tests, normed on fresh representative samples, showed later cohorts scoring markedly higher on earlier editions. Meta-analyses of hundreds of studies placed the gain at about three points per decade in developed countries, larger on fluid reasoning than on crystallized knowledge. [7][11] Reasonable observers noted that nutrition had improved, schooling had lengthened, and societies had grown more complex; these changes offered plausible mechanisms. Twin and adoption studies demonstrated that within a generation heritability was high, yet the between-generation shifts looked environmental. A thoughtful scholar in the late twentieth century could therefore conclude that average intelligence really was rising, even if the gains were uneven and their ultimate meaning unclear. [2][13]

James Flynn’s 1984 analysis of U.S. standardization samples from 1932 to 1978 documented a 13.8-point gain on older tests. The pattern replicated across fourteen nations and on culture-reduced instruments such as Raven’s matrices. These numbers seemed to prove that something potent in the environment was lifting cognitive performance. [4][6] Yet the same data contained warnings. Gains were largest at the lower end of the distribution and did not produce a noticeable renaissance in scientific or cultural achievement. Flynn himself soon argued that the tests measured a correlate of intelligence rather than intelligence proper. [5][11]

Polygenic scores for educational attainment began to show declines across twentieth-century birth cohorts in European Americans, Britons, and Icelanders. Reaction times, a correlate of g, lengthened rather than shortened in controlled modern samples. Brain-volume and brain-weight studies that once appeared to support physical enlargement of intelligence turned out to rest on biased samples. These contrary indicators accumulated gradually and raised growing questions about whether the score gains reflected genuine increases in cognitive capacity. [1]

▶ Supporting Quotes (34)
“Mean IQ rose by 35 points from 1920 to 2013, with almost a third of the increase being in the 1920s and early 1930s.”— How real was the Flynn effect?
“For each successive decade of birth, brain volume increased by 1.7cc for men and by 1.2cc for women. The increase was significant, though small... The younger cohorts may have been bigger-brained because they came disproportionately from a different class of people.”— How real was the Flynn effect?
“Three autopsy datasets... show an increase in brain weight by year of birth from the mid-nineteenth century to the mid-twentieth... these datasets suffer from collection bias, particularly the earlier age cohorts.”— How real was the Flynn effect?
“In Soviet Estonia, cranial volume was measured for an anthropometric survey of students born between 1937 and 1962... Girls with larger crania were more likely to pursue higher education. They thus married later and had fewer children.”— How real was the Flynn effect?
“In all three populations, the mean polygenic score fell from one cohort to the next during the twentieth century.”— How real was the Flynn effect?
“We seem to be taking longer to process the same amount of information... The corresponding decline in IQ is likewise estimated at 1.3 to 1.7 points per decade.”— How real was the Flynn effect?
“It also deals a blow to the Spearman-Jensen theory of intelligence. That theory is based on g, the general intelligence factor.”— Searching for Justice: The Discovery of IQ Gains Over Time
“every manual had a table showing that the publisher's new test had a high correlation with the previous version... Without exception, whenever the same participants were given both the new test and an older test, they had a higher score on the latter.”— Searching for Justice: The Discovery of IQ Gains Over Time
“IQ differences between the generations are clearly environmental in origin. Yet heritability of IQ within generations is robust, which suggested that high within-race heritability estimates do not signal a genetic IQ gap between Black and White populations.”— Searching for Justice: The Discovery of IQ Gains Over Time
“From 1947 to 2002, the developed world saw IQ scores increase markedly–on average, about 3 points a decade for the last 50 years. The mean went up by 18 points in the United States alone on highly g loaded tests such as the Wechsler Intelligence Scale for Children (WISC), the Wechsler Adult Intelligence Scale (WAIS), the Stanford–Binet, the Raven's tests, and the Armed Forces Qualification Test (AFQT).”— The theory of intelligence and its measurement
“In 1984, James Flynn found that American standardization samples, including children, scored systematically higher on older versions of IQ tests than they did on newer versions, reflecting a 13.8-point rise in mean IQ scores between 1932 and 1978 (approximately three points per decade; Flynn, 1984).”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“Meta-analytic estimates have been roughly consistent with Flynn’s original observation of an increase in three IQ points per decade, with measures of fluid intelligence... frequently showing greater gains over time than measures of crystallized intelligence (Pietschnig & Voracek, 2015).”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“multilevel analyses revealed between-subjects Flynn Effects... as well as within-child Flynn Effects on cognitive growth across age. Overall gains equaled approximately three IQ points per decade.”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“When the new test subjects take the older tests, in almost every case their average scores are significantly above 100.”— Flynn effect - Wikipedia
“Some studies have found the gains of the Flynn effect to be particularly concentrated at the lower end of the distribution.”— Flynn effect - Wikipedia
“The hypothesis that best fits the results is that IQ tests do not measure intelligence but rather a correlate with a weak causal link to intelligence.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“The Dutch data prove the existence of unknown environmental factors so potent that they account for 15 of the 20 points gained.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“Although the Flynn effect is widely accepted, most approaches to estimating it have relied upon “scorecard” approaches that make estimates of its magnitude and error of measurement controversial”— The Flynn Effect: A Meta-analysis
“Previous Flynn effect studies were predominantly conceptually based on Cattell’s classic taxonomy, distinguishing between fluid, crystallized, and full-scale IQ. However, according to the currently most widely accepted intelligence theory, the Cattell–Horn–Carroll (CHC) model, fluid and crystallized intelligence are merely two of several broad abilities.”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“IQ gains appear to be predominantly negatively associated with psychometric g (Must et al. 2003; Pietschnig and Voracek 2015; Woodley and Madison 2013; Woodley and Meisenberg 2013; but see Colom et al. 2001 for contrasting findings).”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“In developed countries, measured IQ has been increasing at a rate of approximately .33 IQ points per year for most of the past century, a pattern consistent across both time and geography.”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“An effect of the predicted magnitude was observed for PIAT-Math when maternal IQ was controlled.”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“Although the Flynn effect is widely accepted, most approaches to estimating it have relied upon “scorecard” approaches that make estimates of its magnitude and error of measurement controversial and prevent determination of factors that moderate the Flynn effect across different IQ tests.”— The Flynn Effect: A Meta-analysis
“In his groundbreaking paper, Flynn found evidence “that representative samples of Americans did better and better on IQ tests over 46 years, the total gain amounting to a rise in mean IQ of 13.8 points” (Flynn, 1984).”— What Is The Flynn Effect In Psychology?
“This study found that “across 285 studies (N = 14,031) since 1952 with administrations of 2 intelligence tests with different normative bases, the meta-analytic mean was 2.31…standard score points per decade” (Trahan et al., 2014).”— What Is The Flynn Effect In Psychology?
“What they found was that five, six, seven, eight, nine, ten, eleven, twelve, and thirteen-year-olds’ scores trended up in each year of the survey data. The extent of these trends was similar by sex, race, and urbanicity, but children from more educated and higher-earning households showed a stronger Flynn effect—that is, greater score increases in successive years of the data.”— The Other Type of Flynn Effect
“Oberleiter et al. claimed to find a large (~5-IQ point), measurement invariant anti-Flynn effect—that is, real declining ability—in Germany over a brief ten year period (2012-22). ...there were changes in the underlying population being covered in their comparisons. Their results were based on comparisons of three large, population-representative cohorts of secondary school students, but in this period, secondary school attendance became much less selective.”— The Other Type of Flynn Effect
“Intelligence-test performance has been getting better by around 3 points per decade since IQ testing began, in a phenomenon known as the ‘Flynn Effect’.”— Intelligence: All That Matters
“What, he asked them, do a horse and a dog have in common? A regular answer from the nineteenth-century peasants was: ‘They are both used in hunting.’”— Intelligence: All That Matters
“many of the originators and developers of intelligence tests were supporters of eugenics. We are absolutely right to find repugnant some of the uses to which intelligence testing was put.”— Intelligence: All That Matters
“the immoral beliefs of some of the original scientists are not a reason to dismiss all of their results, many of which, like the existence of the g-factor, are well supported by subsequent research. The fact that, for example, the link between smoking and lung cancer was first discovered by Nazi doctors (Proctor, 2000) doesn’t mean we should tell people that smoking is healthy after all.”— Intelligence: All That Matters
“even if every single Londoner who is currently not working was trained up to do these jobs we would still have a massive number of vacancies, a record number of vacancies in the health sector, in social care sector and hospitality and tech and so forth”— Sadiq Khan: London needs more migrants
“He used the example of an aging workforce in the construction industry and the loss of EU-born workers as proof of the need for “sensible migration””— Sadiq Khan: London needs more migrants
“the positive Flynn effect relates to improved education and nutrition, combined with reduced pathogen stress”— Flynn effect and its reversal are both environmentally caused
How It Spread

Academic journals and textbooks spread the assumption rapidly after Flynn’s 1984 paper. The term Flynn effect, introduced in The Bell Curve, entered psychology curricula and became the most cited environmentalist counterargument in debates over racial IQ differences. Richard Nisbett’s 2009 book relied heavily on the gains to argue for a purely environmental explanation of group differences. [3][5] Test publishers issued new norms without always highlighting how much higher modern samples scored on obsolete versions, quietly embedding the phenomenon in clinical practice. [2]

Military testing programs across Europe supplied raw data on unaltered instruments and lent the effect an aura of official objectivity. Scholars exchanged letters and questionnaires with test directors in thirty-five countries, each confirming local gains and reinforcing the sense of a global phenomenon. Flynn’s 2013 TED Talk brought the idea to a popular audience by noting that people from a century ago would score about 70 on today’s norms. [6][11] Yet the effect was rarely emphasized in clinical training programs, so many practicing psychologists continued to treat IQ scores as stable across generations. [7]

▶ Supporting Quotes (18)
“Named the Flynn effect after intelligence researcher James Flynn, this secular increase in mean IQ has been much debated. How real was it?”— How real was the Flynn effect?
“The tables also showed something persistent and surprising. Without exception, whenever the same participants were given both the new test and an older test, they had a higher score on the latter.”— Searching for Justice: The Discovery of IQ Gains Over Time
“The Flynn Effect remains the most cited and popular idea in the culture-only arsenal. From 1947 to 2002, the developed world saw IQ scores increase markedly ... These articles would probably have remained within the normal purview of psychometrics had Flynn and others not linked the cross-populational phenomenon of secular gains in IQ to the “race issue.””— The theory of intelligence and its measurement
“The FE has had a profound impact on developmental researchers’ conceptualizations of cognitive ability. It provides evidence that broad changes to environments in which children are raised can influence cognitive development, which is driven by a dynamic interplay of genetic and environmental factors.”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“many textbooks on psychology and IQ testing have now followed the lead of Herrnstein and Murray in calling the phenomenon the Flynn effect.”— Flynn effect - Wikipedia
“Over the last decade, scholars in many countries—largely unknown to one another—have been measuring IQ trends from one generation to the next.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“Military authorities in charge of psychological testing were contacted in every European country, plus Australia, Canada, Greenland, Iceland, and New Zealand”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“The Flynn effect is less well known and often not taught in behavioral science training programs (Hagen, Drogin, & Guilmette, 2008).”— The Flynn Effect: A Meta-analysis
“Recent observations have indeed indicated less consistent Flynn effects, with several reports indicating deceleration (e.g., USA: Rindermann and Thompson 2013); stagnation (e.g., Australia: Cotton et al. 2005); or even reversals of test score gains (e.g., Norway: Bratsberg and Rogeberg 2018; USA: Dworak et al. 2023; Austria: Pietschnig and Gittler 2015).”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“The basic empirical status of the Flynn Effect is well- established.”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“The Flynn effect is less well known and often not taught in behavioral science training programs (Hagen, Drogin, & Guilmette, 2008).”— The Flynn Effect: A Meta-analysis
“He explains that “if you score the people a century ago against modern norms, they would have an average IQ of 70. If you score us against their norms, we would have an average IQ of 130” (Flynn, 2013).”— What Is The Flynn Effect In Psychology?
“None of the peer reviewers or editors at Intelligence or any other journal publishing similar analyses noticed the problem either.”— The Other Type of Flynn Effect
“As a consequence, tests now have to be continually ‘re-normed’, with their score of 100 being set to the average of a sample of contemporary people.”— Intelligence: All That Matters
“Many intelligence researchers shy away completely from even using the word ‘intelligence’, replacing it with more neutral, euphemistic terms like ‘cognitive function’ or ‘general mental ability’.”— Intelligence: All That Matters
“Speaking to Channel 4 News, he said: “I’ve no hesitation in saying we need more migrants in London”.”— Sadiq Khan: London needs more migrants
“iodization raised IQ scores by roughly one standard deviation, or 15 points, which implies a nationwide increase in average IQ of 3.5 points”— The Cognitive Effects of Micronutrient Deficiency: Evidence from Salt Iodization in the United States
“Higher SES was related both to a higher starting point in infancy and to greater gains in intelligence over time, with children from low SES families scoring on average 6 IQ points lower at age 2 than children from high SES backgrounds; by age 16, this difference had almost tripled”— Socioeconomic status and the growth of intelligence from infancy through adolescence
Resulting Policies

Atkins v. Virginia in 2002 barred execution of the intellectually disabled, defined in part by an IQ of 70 or below. Courts then faced the question of whether old test scores should be adjusted downward for the Flynn effect. Walker v. True in 2005 established precedent for such correction in capital cases, affecting hundreds of death-row inmates. [7][13] States continued to rely on whichever norms were available at the time of testing, producing inconsistent outcomes that depended on when a defendant had been assessed. [11]

Special-education eligibility in American schools hinged on IQ cutoffs for intellectual disability and on the discrepancy between IQ and achievement for learning disabilities. Each renorming of a major test produced sudden drops in average scores, shrinking or expanding the pool of eligible children and straining district budgets. Clinicians warned of misdiagnosis patterns, but the adjustments were applied unevenly. [4][7] Educational policymakers cited longer schooling as one driver of the gains, justifying expansions of compulsory education on the assumption that more years in class produced real cognitive growth. [5]

▶ Supporting Quotes (11)
“The FE has had an impact in the highly technical field of statistical psychometrics, and probably also in the larger applied field of mental testing in education, the military, employment selection, and clinical psychology.”— The theory of intelligence and its measurement
“In the United States, intellectual disability is commonly identified in part as having an IQ score below 70 (e.g., American Psychiatric Association, 2013).”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“Diagnosis of a learning disability often requires a child’s IQ score to be markedly higher than their achievement score.”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“The duration of average schooling has increased steadily.”— Flynn effect - Wikipedia
“how IQ tests should be used in making between-groups comparisons.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“The most dramatic example in the United States is the determination of intellectual disability in capital punishment cases. These determinations in so-called Atkins hearings represent life and death decisions”— The Flynn Effect: A Meta-analysis
“Demonstration of an intellectual disability or a learning disability is an eligibility criterion for receipt of special education services in schools.”— The Flynn Effect: A Meta-analysis
“The most dramatic example in the United States is the determination of intellectual disability in capital punishment cases. [...] Walker v. True (2005) set a precedent for the consideration of the Flynn effect in capital murder cases.”— The Flynn Effect: A Meta-analysis
“Demonstration of an intellectual disability or a learning disability is an eligibility criterion for receipt of special education services in schools. Kanaya, Ceci, and Scullin (2003a) and Kanaya, Scullin, and Ceci (2003b) documented a pattern of “rising and falling” IQ scores in children diagnosed with an intellectual disability or learning disability as a function of the release date of the new version of an intelligence test.”— The Flynn Effect: A Meta-analysis
“Finally, another reason that the Flynn Effect is so important is because of the role of IQ in intellectual disabilities, especially “in high stakes decisions when an IQ cut point is used as a necessary part of the decision-making process,” such as in “the determination of intellectual disability in capital punishment cases” (Trahan et al., 2014).”— What Is The Flynn Effect In Psychology?
“in 2014, the US Supreme Court ruled a rigid cut-off score of 70 unconstitutional.”— Intelligence: All That Matters
Harm Caused

The assumption shaped life-and-death decisions in the criminal justice system. More than eighty death sentences had been converted to life terms by 2008 because of Flynn adjustments; hundreds more cases remained active. Convicts who scored above 70 on outdated norms sometimes fell below the cutoff once scores were corrected, yet others were executed before the adjustment became routine. [7][13] In special education, renorming caused abrupt swings in diagnoses. A 5.6-point drop when switching tests could push borderline children into or out of eligibility, disrupting services and confusing parents. [4][7]

Policy debates about group differences absorbed the idea that environmental trends could close gaps, fostering unrealistic expectations. The same data were used to argue that genetic explanations for racial disparities were untenable, even as the gains failed to eliminate those disparities. Research agendas were distorted by premature causal theories that treated every point of increase as proof of effective interventions. [2][3][9]

▶ Supporting Quotes (15)
“Massive IQ gains over time test the IQ-intelligence equation, reveal groups who achieve far beyond their mean IQs, and falsify prominent arguments for a genetic racial IQ gap.”— Searching for Justice: The Discovery of IQ Gains Over Time
“reveal groups who achieve far beyond their mean IQs, and falsify prominent arguments for a genetic racial IQ gap.”— Searching for Justice: The Discovery of IQ Gains Over Time
“At a time of increasing attention to IQ variation among subpopulations, the FE promised to absolve the onus of unfavorable social attitudes engendered by these results. The seeming benevolent promise of the FE is that if samples of entire populations in various countries showed secular gains in IQ scores, the lower-scoring subpopulations within these regions would also gain in average IQ. Since the gradual rise in test scores is assumed to approach a saturation (i.e., peak) level, the subpopulation differences in mean IQ should eventually diminish to nonsignificance.”— The theory of intelligence and its measurement
“rates of intellectual disability diagnosis drop steadily in the years prior to the introduction of a new IQ test version... Upon the introduction of a new test version, intellectual disability diagnoses increase significantly... creating a host of challenges for school districts (e.g., allocation of financial and teacher resources).”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“test re-standardization can shrink the gap between IQ and achievement scores, significantly reducing the probability that a child previously diagnosed with learning disability using an old test version will be re-diagnosed. This creates an opposite problem... Abruptly losing special education resources can be extremely difficult for children.”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“During the 1960s, when some Virginia counties closed their public schools to avoid racial integration, compensatory private schooling was available only for White children. On average, the scores of African-American children who received no formal education during that period decreased at a rate of about six IQ points per year.”— Flynn effect - Wikipedia
“this mass of data poses fundamental problems for developmental psychology, primarily concerning what factors have the most potent effect on IQ, what IQ tests measure”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“In 2008, a report indicated that since the reversal of the death penalty in Atkins’ case, 80+ death penalty pronouncements have been converted to life in prison (Blume, 2008).”— The Flynn Effect: A Meta-analysis
“the authors reported a 5.6-point reduction in IQ score for children initially tested with the WISC-R and subsequently tested with the WISC-III, with a significantly greater proportion of these children being diagnosed with an intellectual disability”— The Flynn Effect: A Meta-analysis
“Development of causal theories, though tempting, may still be premature. Rodgers (1998)... suggested that “research addressing the legitimacy and meaning of the effect should precede research testing for and evaluating causes”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“suppose the WISC-R had been administered in 1992, 20 years after the test was normed. The Flynn effect would have inflated test norms by 0.3 points per year between the year in which the test was normed (1972) and the year in which the test was administered (1992). Correction for that inflation would reduce the person’s IQ score by six points [...] In 2008, a report indicated that since the reversal of the death penalty in Atkins’ case, 80+ death penalty pronouncements have been converted to life in prison (Blume, 2008).”— The Flynn Effect: A Meta-analysis
“Additionally, IQ plays a role in “determining eligibility for special education and American Disability Act services and Social Security Disability Insurance (SSDI) in the United States” (Trahan et al., 2014).”— What Is The Flynn Effect In Psychology?
“There are surprisingly many papers out there that conflate ‘the Flynn effect’, as in the psychometric bias-driven change in scores between cohorts, with ‘the Flynn effect’, as in the sampling bias-driven change in scores between select cohorts. ...it misleads people into thinking that there are oftentimes huge and fast population-level changes that just are not so.”— The Other Type of Flynn Effect
“imagine someone gets a score of just above 70 on a test that was ‘normed’ a few decades before they took it. The bell curve will have marched upwards since the norming, and the convict’s score would be several points lower if the Flynn Effect were taken into account.”— Intelligence: All That Matters
“Many intelligence researchers shy away completely from even using the word ‘intelligence’, replacing it with more neutral, euphemistic terms like ‘cognitive function’ or ‘general mental ability’.”— Intelligence: All That Matters
Downfall

Mounting evidence began to challenge the interpretation that the gains represented real increases in intelligence. Polygenic scores for educational attainment declined across cohorts, reaction times lengthened, and brain-size studies were exposed as biased by sampling. Flynn himself concluded that the tests measured abstract problem-solving with little practical payoff and called the gains “ersatz.” [1][5] Meta-analyses documented that the effect was slowing or reversing in developed countries after the 1990s, with different trajectories for different abilities. [5][11]

Austrian data from 2005 to 2018 showed score gains alongside a weakening positive manifold, the very pattern of correlations that defines g. Measurement invariance tests confirmed the changes were real but indicated they reflected ability differentiation rather than uniform intelligence growth. [8] Sibling fixed-effects analyses of large U.S. samples eliminated the apparent Flynn effect once maternal age and fertility timing were properly controlled, turning the trend slightly negative. [12] Critics increasingly argued that IQ tests yield only ordinal scales unsuitable for secular comparisons and that the gains largely reflect test-specific skills or familiarity. A substantial body of experts now questions whether the twentieth-century rise in raw scores ever reflected a genuine increase in the capacity for intelligence. [3][6][9]

▶ Supporting Quotes (27)
“The mean EA polygenic score fell at a rate of about 0.010 standard deviation per decade.”— How real was the Flynn effect?
“The increase in brain size may therefore reflect a more representative sampling of the population.”— How real was the Flynn effect?
“a similar lengthening of reaction time has been shown by controlled studies with Swedish, Scottish, and American participants – particularly for cohorts born since 1980.”— How real was the Flynn effect?
“Data from 73 studies containing 7,500 participants ages 2 to 48 years showed that between 1932 and 1978, White Americans had gained 14 IQ points.”— Searching for Justice: The Discovery of IQ Gains Over Time
“Figure 2 shows that the bottom 90% of Britons born in 1877 fall below the fifth percentile of those born in 1967, which is to say below an IQ of 75 calculated on 1967 norms.”— Searching for Justice: The Discovery of IQ Gains Over Time
“In 1981, I began an analysis of Armed Forces mental tests that revealed that Blacks had been gaining on Whites (Flynn, 1987a, p. 235).”— Searching for Justice: The Discovery of IQ Gains Over Time
“The problem with IQ tests and virtually all other scales of mental ability in popular use is that the scores they yield are only ordinal (i.e., rank-order) scales; they lack properties of true ratio scales, which are essential to the interpretation of the obtained measures. ... ‘The crux of the problem is that ordinal level measures are not adequate to answer the questions we have posed.”— The theory of intelligence and its measurement
“IQ gains in developed regions appear to have decelerated over the past century (Pietschnig & Voracek, 2015), and evidence suggests that scores have even started to decline slightly (Sundet et al., 2004; Teasdale & Owen, 2005, 2008).”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“Kaufman (2010), for example, asserted that the content, administration, and scoring of the Similarities subtest changed so substantially... Changes in test-taking behavior have also been cited as a measurement artifact.”— Genetically informed, multilevel analysis of the Flynn Effect across four decades and three WISC versions
“In 1987, Flynn took the position that the very large increase indicates that IQ tests do not measure intelligence but only a minor sort of 'abstract problem-solving ability' with little practical significance. He argued that if IQ gains did reflect intelligence increases, there would have been consequent changes of our society that have not been observed (a presumed non-occurrence of a 'cultural renaissance').”— Flynn effect - Wikipedia
“Some researchers have suggested the possibility of a mild reversal in the Flynn effect (i.e., a decline in IQ scores) in developed countries, beginning in the 1990s... Pietschnig and Voracek (2015) reported, in their meta-analysis of studies involving nearly 4 million participants, that the Flynn effect had decreased in recent decades.”— Flynn effect - Wikipedia
“Data from 14 nations reveal IQ gains ranging from 5 to 25 points in a single generation. Some of the largest gains occur on culturally reduced tests and tests of fluid intelligence.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“Dutch men had gained a total of 1.4068 SDs. Multiplying 1.4068 times 15 (15 = 1 SD) yields a total gain of 21.10 IQ points over a period of 29.5 years.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“The Norwegian data show that a nation can make significant gains on a culturally reduced test while suffering losses on other tests.”— Massive IQ Gains in 14 Nations: What IQ Tests Really Measure
“Walker v. True (2005) set a precedent for the consideration of the Flynn effect in capital murder cases.”— The Flynn Effect: A Meta-analysis
“Across 285 studies (N = 14,031) since 1951 with administrations of two intelligence tests with different normative bases, the meta-analytic mean was 2.31, 95% CI [1.99, 2.64], standard score points per decade.”— The Flynn Effect: A Meta-analysis
“Our analyses revealed positive Flynn effects across all domains of the IQ test (Cohen’s d from 0.21 to 0.91) but a trend toward decreasing strength in the positive manifold of intelligence (R2 from .908 to .892), though these changes were not statistically significant.”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“Cross-temporal comparisons of test scores based on non-measurement invariant test instruments can yield misleading results... Here, we examined cross-temporal changes of the positive manifold between 2005 and 2018 in three standardization samples of a well-established intelligence test in Austria based on raw scores and measurement invariant latent means.”— Increasing IQ Test Scores and Decreasing g: The Flynn Effect and Decreasing Positive Manifold Strengths in Austria (2005–2018)
“Flynn (1996) consistently referred to “ersatz intelligence gains,” suggesting that the effect is an artifact. Wicherts et al. (2004) found lack of factorial invariance in the Flynn Effect across cohorts”— Identification of a Flynn Effect in the NLSY: Moving from the center to the boundaries
“Across 285 studies (N = 14,031) since 1951 with administrations of two intelligence tests with different normative bases, the meta-analytic mean was 2.31, 95% CI [1.99, 2.64], standard score points per decade. [...] The mean effect size for 53 comparisons (N = 3,951) [...] involving modern (since 1972) Stanford-Binet and Wechsler IQ tests (2.93, 95% CI [2.3, 3.5], IQ points per decade) was comparable to previous estimates of about 3 points per decade, but not consistent with the hypothesis that the Flynn effect is diminishing. [...] For modern tests, [...] age and ability level were not significant moderators.”— The Flynn Effect: A Meta-analysis
“Some researchers have found evidence for a “negative Flynn Effect,” that is, that the Flynn Effect has actually begun to reverse (Dutton et al., 2016, as cited in Bratsberg & Rogeberg, 2018; Pietschnig & Voracek, 2015, as cited in Bratsberg & Rogeberg, 2018).”— What Is The Flynn Effect In Psychology?
“In this paper, Flynn looked at increases in IQ in 14 nations and concluded that “IQ tests do not measure intelligence but rather a correlate with a weak causal link to intelligence” (Flynn, 1987).”— What Is The Flynn Effect In Psychology?
“It’s only when we compare siblings in the same family that we see the effect entirely evaporate. In fact, it goes slightly negative!”— The Other Type of Flynn Effect
“The issues with this result were two-fold. First, their result was not, in fact, measurement invariant. ...Second, there were changes in the underlying population being covered in their comparisons.”— The Other Type of Flynn Effect
“Flynn, along with other IQ researchers, thinks the answer is no to both these questions. He argues that improved nutrition and education are only part of the explanation”— Intelligence: All That Matters
“But on the speed test there was no generational difference whatsoever.”— Intelligence: All That Matters
“many of which, like the existence of the g-factor, are well supported by subsequent research.”— Intelligence: All That Matters
Sources
Related False Assumptions
ID: FA-20260216-c759a683 · Created: 2026-02-16T05:16:55.505664 · Schema v3

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