Grit vs IQ

Posted on September 29, 2026 by Mahesh

Understanding IQ

Grit vs IQ: Which Predicts Success More? What the Studies Found

Grit is weakly to moderately linked to school achievement and overlaps almost completely with conscientiousness. See what the original grit studies, two large meta-analyses, the marshmallow test and a retracted test-motivation paper really show about grit vs IQ.

By Alden Cross, Intelligence Research WriterPublished September 29, 2026 · 10 min readReviewed by Aarav Vardhan, Editor-in-Chief

Three cards compare correlations. Grit and school achievement: a weighted correlation of .19 across 137 studies and 285,331 people. Grit and conscientiousness: a corrected correlation of .84 across 88 samples and 66,807 people. Intelligence and school grades: a corrected correlation of .54 across 240 samples and 105,185 people, corrected for range restriction, so not like for like with the grit figures.

Grit vs IQ: does perseverance beat intelligence? In the research, no. Two large reviews find that grit correlates only weakly to moderately with school achievement (a weighted correlation of .19 across 137 studies), while a review of 240 samples puts intelligence tests and school grades at .54 after corrections. Grit also overlaps almost completely with the Big Five trait of conscientiousness (.84) and is nearly unrelated to cognitive ability (.05). It behaves like a separate effort trait that adds a little to IQ, not a replacement for it. This guide walks through the original grit studies, the meta-analyses, the marshmallow test, and a widely repeated claim about paying people to raise their IQ scores that was retracted in 2025.

Grit and school achievement: a weighted correlation of .19 across 137 studies and 285,331 people, roughly 4% of the differences in achievement.
Grit and conscientiousness: a corrected correlation of .84, so close to the same trait; overall grit adds almost nothing once conscientiousness is counted.
Grit and cognitive ability: about .05 corrected, meaning grittier people are not systematically smarter or less smart.
Marshmallow test: the link to teenage achievement shrank by about two thirds once family background and early cognitive ability were controlled.
Retraction: the 2011 paper behind “paying people adds 10 IQ points” was retracted by its journal on 1 May 2025.

What is grit, and how is it measured?

Grit is defined as perseverance and passion for long-term goals. The psychologist Angela Duckworth and colleagues introduced it in a 2007 paper in the Journal of Personality and Social Psychology, along with a questionnaire. The original Grit Scale has 12 items split into two factors of six: consistency of interests and perseverance of effort. People rate each item from 1 to 5, and a short 8-item version, the Grit-S, was published in 2009. Both are scored by averaging, so the maximum is 5. Everything rests on self-report, which matters later. If you are weighing effort against ability in a wider sense, our guides to growth mindset and intelligence and talent versus practice cover the neighboring evidence.

What did the original grit studies find?

The 2007 paper reported six studies. Its abstract says grit “accounted for an average of 4% of the variance in success outcomes” and showed incremental predictive validity over IQ and conscientiousness. Incremental means it added something on top, not that it outranked anything. The table shows what each sample actually found, including the parts that rarely make it into popular summaries.

The 2007 grit paper, sample by sample
Sample	What grit predicted	How IQ-type scores compared
Adults aged 25 and older (N = 1,545 and 690)	More schooling than same-age peers; one standard deviation of extra grit meant 35% lower odds of being a frequent career changer	No IQ measure; analyses controlled for age and the Big Five
Psychology majors at an Ivy League university (N = 138)	GPA, r = .25 (and .34 with SAT held constant)	SAT and GPA r = .30; grit and SAT r = −.20, so the grittier students had slightly lower SAT scores
West Point cadets (N = 1,218 and 1,308)	Finishing the first summer of training; about 1 in 20 cadets dropped out, and one standard deviation of grit meant more than 60% higher odds of finishing (Study 4)	West Point’s own Whole Candidate Score, built from SAT, class rank, leadership and fitness, did not predict who finished
Spelling Bee finalists aged 7 to 15 (N = 175)	Reaching a later round, with age controlled	With verbal IQ and age in the model, grit was no longer statistically significant; verbal IQ was

Two details deserve emphasis. Grit did not relate positively to IQ in these samples, so it is not a proxy for intelligence; at the Ivy League school it was slightly negatively related to SAT scores, and the authors speculated that smarter students “may be slightly less gritty.” But the Spelling Bee result cuts the other way from how grit is often described: once verbal IQ entered the model, grit stopped being a significant predictor, though the authors noted that missing IQ data cut the degrees of freedom by more than half. The samples are also highly selected, which shrinks IQ correlations as well as grit ones.

What do the big reviews say about grit?

Two large meta-analyses give the clearest picture. Credé, Tynan and Harms (2017) pooled 88 independent samples and 66,807 people. Grit correlated .18 with academic performance after correction for measurement error (.15 uncorrected), and .84 with conscientiousness, but only .05 with cognitive ability. After conscientiousness was accounted for, overall grit explained no additional variance in overall academic performance or high-school GPA and almost none for college GPA. Only the perseverance-of-effort half of grit added a small amount, and the meta-analysis did not confirm the two-part structure the scale assumes. Lam and Zhou (2022) covered 137 studies and 285,331 people and found a weighted correlation of .19 between grit and academic achievement, .21 for perseverance of effort and .08 for consistency of interest.

A UK twin study points the same way. Rimfeld and colleagues studied 4,642 sixteen-year-olds from the Twins Early Development Study. The Big Five personality traits explained 5.6% of the variance in GCSE grades, and adding grit raised that by only 0.5 percentage points. Perseverance of effort was 37% heritable, and its genetic correlation with conscientiousness was .86. That study used no intelligence measure, so it tests grit against personality rather than against IQ.

How the correlations line up (corrected figures are not like for like)
Relationship	Correlation	Study and sample
Grit and academic performance	.18 corrected (.15 observed)	Credé et al. 2017: 88 samples, 66,807 people
Grit and academic achievement	.19 weighted, observed	Lam and Zhou 2022: 137 studies, 285,331 people
Grit and cognitive ability	.05 corrected	Credé et al. 2017: 21 samples, 11,513 people
Intelligence tests and school grades	.54 corrected, incl. range restriction	Roth et al. 2015: 240 samples, 105,185 people
Cognitive tests and job performance	.31 (2022 re-estimate; .51 in 1998)	Sackett et al. 2022, employees
Conscientiousness and job performance	.19 (2022; .31 in 1998)	Sackett et al. 2022, employees

These are not like-for-like comparisons, so read the table as a map, not a scoreboard. The .54 is corrected for measurement error and range restriction and comes from school grades; grit’s .18 is corrected for measurement error only; the .19 is an uncorrected average. Job-performance validity for cognitive tests is itself contested: the older .51 figure was re-estimated at .31 in 2022 after Sackett and colleagues argued that earlier range-restriction corrections were too generous, and structured interviews now top that table. Even so, the direction is consistent: in these reviews cognitive ability shows a larger correlation with outcomes than grit or conscientiousness does, which fits our guides to whether IQ predicts school success and what a cognitive test at work predicts. For personality more broadly, see IQ versus personality.

What about self-control and the marshmallow test?

Self-control is a nearby idea with better evidence behind it. The Dunedin study followed a complete birth cohort of 1,037 children in New Zealand to age 32, with 96% still taking part. Childhood self-control, rated from nine measures between ages 3 and 11, predicted adult health, substance dependence, finances and criminal convictions “even after accounting for social class origins and IQ,” and the pattern held in a sibling comparison of about 500 pairs. It is not a contest with IQ, though: in that cohort self-control and IQ correlated .44, and the design is observational, so it shows self-control adds prediction beyond IQ, not that it exceeds it.

The marshmallow test is weaker than its reputation. Watts, Duncan and Quan (2018) ran a conceptual replication on a larger, more varied sample: 918 US children with valid delay data, with the main analyses on 552 whose mothers had not completed college. An extra minute of waiting at age 4 went with about a tenth of a standard deviation in achievement at 15, an association about half the size of the original. It fell by two thirds with controls for family background, early cognitive ability and the home environment, and became non-significant once early cognitive and behavioral measures were added (standardized coefficient .24, then .08, then .05). Most of the variation came from whether a child could wait at least 20 seconds. How much a home can shape such traits at all is a different question; see our guide to adoption and IQ.

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Does motivation change IQ test scores? A retracted claim

A popular argument runs that IQ tests mostly measure motivation, because paying people raises their scores by about 10 points. It traces to a 2011 paper by Duckworth and colleagues in PNAS, which reported a meta-analytic effect of 0.64 standard deviations (about 9.6 points on a scale with a standard deviation of 15, our conversion; the paper reports standard-deviation units only). That paper was retracted on 1 May 2025. The journal issued an expression of concern in February 2025, and in the retraction notice the authors explained that a retracted 1978 article had contributed three large effect sizes and 24% of the meta-analytic sample. Without it the effect fell to 0.47; after adjusting for publication bias it was 0.16, with a confidence interval (−0.02 to 0.34) that includes zero. All four publication-bias tests now indicated bias, and the authors decided to retract the article.

What survives is narrower. Effort and engagement plausibly affect any test performance, which is why conditions matter, as covered in our guide to the factors that affect IQ test results and the news piece on what practice actually changes. But a ten-point payment bonus is not an established fact, and it should not be repeated as one.

What should you take from grit vs IQ?

Treat it as both, not either. IQ predicts school and job outcomes moderately; grit and conscientiousness add a small, real increment on top.
Ask which half of grit you mean. Perseverance of effort carries the prediction; consistency of interest adds little.
Do not use grit scores to judge people or schools. Duckworth wrote in 2016 that she worried she had “contributed, inadvertently,” to high-stakes character testing, and a 2015 review by her and Yeager concluded that no available measure suits between-school accountability.
Expect self-report bias. High-performing charter-school students rated themselves lower on grit than district-school peers in Duckworth’s own data.
Be cautious about grit interventions. The correlations are modest and observational, and we did not review any trial showing that raising grit raises achievement.

For a wider view of what predicts success beyond a single score, see our guides to IQ versus EQ and whether IQ predicts income, and for a condition where persistence and instruction interact, dyslexia and IQ.

Quick answers

Is grit more important than IQ? No source we reviewed supports that. Grit adds a small amount to prediction; cognitive ability predicts school grades more strongly in the largest reviews, though the figures are not like for like.
Is grit the same as conscientiousness? Almost. The corrected correlation is .84, and the twin study found a genetic correlation of .86 for perseverance of effort.
Are gritty people smarter? No. Grit and cognitive ability correlate about .05.
Does the marshmallow test predict success? Weakly. The link to age-15 achievement shrank by two thirds with controls and lost significance with early cognitive measures.
Does paying people raise IQ scores by 10 points? Not established: the paper that claimed it was retracted in 2025.
Can you measure grit reliably? Mostly by self-report, and its author says character questionnaires are not ready for high-stakes use.

The bottom line

Grit is real enough as a label for sustained effort, but the evidence does not support the claim that it beats intelligence. Across the largest reviews it correlates weakly to moderately with achievement, overlaps almost completely with conscientiousness, and adds very little once that trait is counted. The best-supported version of the grit story is modest: talent and sustained effort both matter, effort is hard to measure, and neither a marshmallow nor a payment can be read as a shortcut to a score.

Sources

Duckworth, A.L., Peterson, C., Matthews, M.D. and Kelly, D.R. (2007): Grit: perseverance and passion for long-term goals, Journal of Personality and Social Psychology, 92(6), 1087-1101.
Duckworth, A.L. and Quinn, P.D. (2009): Development and validation of the Short Grit Scale (Grit-S), Journal of Personality Assessment, 91(2), 166-174.
Credé, M., Tynan, M.C. and Harms, P.D. (2017): Much ado about grit: a meta-analytic synthesis of the grit literature, Journal of Personality and Social Psychology, 113(3), 492-511.
Lam, K.K.L. and Zhou, M. (2022): Grit and academic achievement: a comparative cross-cultural meta-analysis, Journal of Educational Psychology, 114(3), 597-621.
Rimfeld, K., Kovas, Y., Dale, P.S. and Plomin, R. (2016): True grit and genetics: predicting academic achievement from personality, Journal of Personality and Social Psychology, 111(5), 780-789.
Roth, B. et al. (2015): Intelligence and school grades: a meta-analysis, Intelligence, 53, 118-137.
Sackett, P.R., Zhang, C., Berry, C.M. and Lievens, F. (2022): Revisiting meta-analytic estimates of validity in personnel selection: addressing systematic overcorrection for restriction of range, Journal of Applied Psychology, 107(11), 2040-2068.
Moffitt, T.E. et al. (2011): A gradient of childhood self-control predicts health, wealth, and public safety, PNAS, 108(7), 2693-2698.
Watts, T.W., Duncan, G.J. and Quan, H. (2018): Revisiting the marshmallow test: a conceptual replication investigating links between early delay of gratification and later outcomes, Psychological Science, 29(7), 1159-1177.
PNAS (2025): Retraction for Duckworth et al., “Role of test motivation in intelligence testing,” PNAS, 122(18), e2508040122.
Duckworth, A.L. and Yeager, D.S. (2015): Measurement matters: assessing personal qualities other than cognitive ability for educational purposes, Educational Researcher, 44(4), 237-251.
Duckworth, A.L. (2016): Don’t grade schools on grit, The New York Times, 26 March 2016.

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In the old clinical scheme a moron had an IQ of roughly 50 to 70, an imbecile about 20 or 25 to 50 and an idiot below that, according to Lewis Terman in 1916. See who coined the words, how the cut-offs moved, what the 1913 UK Act said and why the labels were dropped.

By Leon Falkner, Data & Research AnalystPublished September 29, 2026 · 11 min readReviewed by Aarav Vardhan, Editor-in-Chief

A bar chart draws the 1916 classification of Lewis Terman on an IQ scale from 0 to 150. The three retired labels are highlighted: idiot below 20 or 25, imbecile 20 or 25 to 50 and moron 50 to 70, with adult mental levels of up to about 3, 3 to 7 and about 7 to 11 years. The other bands run from border-line deficiency at 70 to 80 up to near genius above 140.

What IQ is a moron? In the old clinical scheme, a “moron” was someone with the mildest form of what is now called intellectual disability, and in Lewis Terman’s 1916 Stanford-Binet tables the group sat at an IQ of roughly 50 to 70. An “imbecile” sat at about 20 or 25 up to 50, and an “idiot” below that. These were never official cut-offs. The original 1910 definitions counted mental age, not IQ; different authorities drew the lines in different places; and Terman himself called the sub-grade bands “not very secure.” This guide covers who defined each word, how the lines moved, what a 1913 UK Act said, why the words were dropped and what replaced them. All three words are offensive today and are quoted here only as history.

Moron: an IQ of roughly 50 to 70 in Terman’s 1916 tables; a mental age of about 7 or 8 up to 12 in the 1910 scheme.
Imbecile: an IQ of about 20 or 25 to 50; a mental age of 3 to 7.
Idiot: an IQ below about 20 or 25; a mental age of up to about 2 or 3.
Origin: “moron” was coined as a new technical term in 1910, from a Greek word for foolish; “idiot” and “imbecile” are far older.
Retired: Rosa’s Law (2010) replaced “mental retardation” with “intellectual disability” in US federal law, and DSM-5 (2013) bases severity on everyday functioning, not IQ bands.

What IQ was a moron, an imbecile and an idiot?

The nearest thing to an original IQ table comes from Lewis Terman’s 1916 The Measurement of Intelligence, which introduced the Stanford-Binet in the United States (see our guide to the Stanford-Binet). Terman labeled every IQ below 70 “definite feeble-mindedness” and then subdivided the group: those between 50 and 70 “include most of the morons,” those between 20 or 25 and 50 are “ordinarily to be classed as imbeciles,” and those below 20 or 25 are idiots. He also translated the three grades into the mental level of an adult, shown next to the 1910 mental-age bands in the table.

The three labels in two old systems
Old label	IQ band (Terman, 1916)	Adult mental level (Terman)	Mental age (1910 scheme, as Goddard reported it)
Idiot	below 20 or 25	up to about 3 years	up to and including 2 years
Imbecile	20 or 25 to 50	3 to 7 years	3 to 7 years, inclusive
Moron	50 to 70 (“most of the morons”)	about 7 to 11 years	7 to 12 years; some sources say 8 to 12

The tidy version that circulates online — idiot 0 to 25, imbecile 26 to 50, moron 51 to 70 — is a later simplification, and we found no primary source that prints it. Terman’s own version has “or” boundaries at 20 or 25, says 50 to 70 covers most morons, and adds that the lines between such groups are “absolutely arbitrary, a matter of definition only.” Sources also disagree by a year at each end of the mental-age bands: Goddard’s 1914 book gives the moron range as 7 to 12, the Online Etymology Dictionary gives 8 to 12, and Terman’s adult figure is about 7 to 11.

Where did the words come from?

Two of the three are far older than IQ testing. Idiot comes from the Greek idiotes, a “private person” or layman, and by the early fourteenth century English used it for a person unable to reason. Imbecile comes from the Latin imbecillus, “weak, feeble,” and first described bodily weakness in the 1540s; the mental sense arrived in the mid-eighteenth century. Moron is different: it was invented for the job.

In 1910 the American Association for the Study of the Feeble-Minded adopted a three-grade scheme, and the psychologist Henry H. Goddard supplied a new word for the top grade, taken from the Greek moros, “foolish, dull.” Goddard’s 1914 book Feeble-Mindedness: Its Causes and Consequences reports the scheme in mental-age years: idiots up to and including two, imbeciles three to seven and, in his words, “for those from seven to twelve a new term has been invented; they are now called morons.” He added that the new word “designates almost exactly what is meant by ‘feeble-minded’ in England.” Coined as a clinical term in 1910, “moron” was in print as an insult by 1918 and was later dropped from technical use, according to the Online Etymology Dictionary.

How did mental ages become IQ bands?

Mental age is the age at which an average child performs like the person tested. A ratio IQ divides it by chronological age and multiplies by 100, so a child of 10 with a mental age of 5 scores 50. Adults cause a problem, because mental age stops rising in the mid-teens. Terman handled it by ignoring age above 16; his case notes give scores such as “approximately 65 (not counting age beyond 16).” Using 16 as the divisor (our arithmetic), a mental age of 8 is an IQ of 50 and a mental age of 11 is about 69. That is why “IQ 50 to 70” and “an adult mental age of about 7 to 11” describe nearly the same people, and why Goddard’s upper limit of 12 works out nearer to IQ 75. Modern tests no longer report mental age at all. Our guides to IQ and mental age and deviation IQ versus ratio IQ explain why, and the piece on standard deviation 15 versus 16 explains why older scales do not line up with today’s.

Who drew the line where?

The words disappeared, but the underlying question — where does the line sit? — kept moving. The table shows how far the cut-off wandered over a century.

How authorities drew the line, 1910 to today
Authority and year	Term used	Where the line sat
Goddard and the American Association, 1910 (as reported in 1914)	idiot, imbecile, moron	mental age up to 2; 3 to 7; 7 to 12. No IQ figures.
Terman, Stanford-Binet, 1916	“definite feeble-mindedness”	IQ below 70; morons mostly 50 to 70
Kuhlmann (as quoted by Wechsler)	mental defectives	IQ below 75
Wechsler-Bellevue, 1944	defective; borderline	65 and below; 66 to 79
WAIS, as tabulated in Wechsler’s 1958 book	defective; borderline	69 and below; 70 to 79
AAMD manual, 1959	mental retardation, borderline included	one standard deviation below the mean (about 85 on today’s scale of 15); “almost 15 percent” of the US population
AAMD manual, 1973	mental retardation	back to about 70; the ceiling may extend to 75
DSM-IV-TR, 2000 (as quoted in Atkins v. Virginia)	“mild” mental retardation	an IQ of 50–55 to approximately 70
DSM-5, 2013	intellectual disability	about two standard deviations below the mean (an IQ of about 70 or below), plus limits in everyday functioning
AAIDD, current definition	intellectual disability	“around 70 or as high as 75,” plus adaptive limits and onset before age 22

The 1959 row is the striking one. The American Association on Mental Deficiency moved the line to one standard deviation below the mean, a step its own 1973 manual says could take in almost 15 percent of the US population, and then reversed it. On a normal curve the share of people below 85 is 15.9 percent (our calculation). A cut-off is a decision, not a discovery, and the same person could sit inside or outside a diagnosis depending on which manual was in force. Note that Wechsler’s tables never used the three words at all; his labels were “defective” and “borderline.”

What did UK law say? The Mental Deficiency Act 1913

British law used the same vocabulary and defined it differently. Section 1 of the Mental Deficiency Act 1913 named four classes, each by what a person could do rather than by any test score: idiots, unable “to guard themselves against common physical dangers”; imbeciles, “incapable of managing themselves or their affairs”; feeble-minded persons, who needed “care, supervision, and control”; and “moral imbeciles,” defined by a permanent mental defect coupled with “strong vicious or criminal propensities.” The statute contains no IQ or mental-age figure. Goddard himself observed that his new American word “moron” covered almost exactly what the English called “feeble-minded.” The Mental Health Act 1959 later replaced the four classes with “severe subnormality” and “subnormality,” and British services now say “learning disability,” which means what the United States calls intellectual disability — a terminology trap covered in our guide to low IQ, intellectual disability and learning disability.

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Why were the words dropped?

A clinical word for a stigmatized condition tends to turn into an insult, and its replacement then absorbs the stigma. “Moron” made the jump within about eight years of its coinage. The field’s response was to keep changing the label: by 1973 the American Association on Mental Deficiency’s manual was titled Manual on Terminology and Classification in Mental Retardation, and in 2010 Congress passed Rosa’s Law (Public Law 111-256, signed 5 October 2010), which replaced “mental retardation” with “intellectual disability” in a list of federal education, health and rehabilitation statutes. The law renamed rather than redefined: its own text says the new term means a condition previously referred to as mental retardation. The Social Security Administration made the same substitution in its disability listings from 3 September 2013, and DSM-5 renamed the diagnosis the same year.

What were the labels used to justify? Buck v. Bell

The categories were not harmless bookkeeping. In Buck v. Bell (1927) the US Supreme Court upheld Virginia’s compulsory sterilization law, and Justice Holmes closed the opinion with the line “Three generations of imbeciles are enough.” The opinion itself describes Carrie Buck, her mother and her daughter as “feeble-minded” and states no IQ or mental age; “imbeciles” appears only in that sentence. Lutz Kaelber of the University of Vermont counts compulsory sterilization laws in over 30 US states that led to more than 60,000 sterilizations of disabled people. The wider story of how IQ testing was bent to that agenda, and where the popular version overreaches, is in our guide to eugenics and the history of IQ testing.

How is intellectual disability defined today?

Modern diagnosis is not “an IQ below 70.” DSM-5 requires limits in intellectual functioning and in adaptive functioning across conceptual, social and practical skills, and describes the intellectual limit as roughly two standard deviations below the population mean, an IQ of about 70 or below. The American Association on Intellectual and Developmental Disabilities says a score “around 70 or as high as 75” indicates a significant limitation and places onset before age 22. The World Health Organization’s ICD-11 describes the mild range as roughly two to three standard deviations below the mean. Severity is now set by everyday functioning rather than by an IQ band. Our guide to what an IQ of 70 means explains the measurement-error zone around the line, and our news pieces on the Hamm v. Smith decision and the Social Security score rules show how courts and benefit rules handle the same numbers.

The bell curve helps here, with one warning. On a normal model with a mean of 100 and a standard deviation of 15, about 2.3 percent of people would score below 70 (roughly 1 in 44), 0.04 percent below 50 (roughly 1 in 2,300) and almost nobody below 25. Those are model figures, not prevalence counts: the American Psychiatric Association puts intellectual disability at about 1 percent of the population, well under the 2.3 percent the curve implies, because a diagnosis also needs limits in daily functioning. Our IQ percentile calculator and IQ bell curve pages let you check any score. One more confusion worth clearing: dyslexia and other specific learning disorders are not intellectual disability and occur at any IQ, as our guide to dyslexia and IQ explains.

Quick answers

What IQ is a moron? Roughly 50 to 70 in Terman’s 1916 tables; a mental age of about 7 or 8 up to 12 in the 1910 scheme.
What IQ is an imbecile? About 20 or 25 to 50 in Terman’s tables; a mental age of 3 to 7.
What IQ is an idiot? Below about 20 or 25; a mental age of up to about 2 or 3.
Who invented the word “moron”? Henry H. Goddard proposed it in 1910, from the Greek moros, and the American Association for the Study of the Feeble-Minded adopted it.
Was there ever an official IQ table for the three words? No. The 1910 scheme used mental age, and Terman’s IQ bands were approximate suggestions he called “not very secure.”
Are the words still used in diagnosis? No. Current manuals say intellectual disability (UK services say learning disability), and the old words survive only as insults.
Is IQ 70 the modern cut-off? It is a guide, not a line: about 70 to 75, plus limits in everyday functioning that begin in the developmental period.

The bottom line

“Moron,” “imbecile” and “idiot” began as the three grades of one clinical scale, defined first by mental age in 1910 and then given approximate IQ bands by Terman in 1916: about 50 to 70, 20 or 25 to 50, and below that. The bands were soft from the start, the cut-off for the whole group moved by a full standard deviation within living memory, and the words turned into insults within a decade. What replaced them is not a new set of IQ labels but a two-part test — a low score plus limits in everyday life — that no online quiz can apply.

Sources

Terman, L.M. (1916): The Measurement of Intelligence. Houghton Mifflin, pp. 78-80.
Goddard, H.H. (1914): Feeble-Mindedness: Its Causes and Consequences. Macmillan, pp. 3-4.
Wechsler, D. (1958): The Measurement and Appraisal of Adult Intelligence, 4th ed. Williams & Wilkins.
Grossman, H.J., ed. (1973): Manual on Terminology and Classification in Mental Retardation. American Association on Mental Deficiency.
Online Etymology Dictionary: entries for moron, idiot and imbecile.
Mental Deficiency Act 1913 (3 & 4 Geo. 5 c. 28), section 1, transcription.
Buck v. Bell, 274 U.S. 200 (1927).
Atkins v. Virginia, 536 U.S. 304 (2002), footnote 3 (DSM-IV-TR).
Rosa’s Law, Public Law 111-256 (2010).
Social Security Administration (2013): Change in terminology, mental retardation to intellectual disability, 78 FR 46499.
American Psychiatric Association: DSM-5 fact sheet, Intellectual Disability.
AAIDD: Definition of intellectual disability.
Kaelber, L.: Eugenics, compulsory sterilization in 50 American states, University of Vermont.
World Health Organization: ICD-11, code 6A00.0, mild disorder of intellectual development.

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Understanding IQ

Creativity and IQ: What the Threshold Theory Gets Wrong

Creativity and IQ correlate only weakly. The largest meta-analysis ever run on the question, covering 45,880 people, found no significant threshold at IQ 120, just a modest overall link of about .17 to .25. See what the strongest evidence shows, and why the classic claim does not hold up.

By Arjun Vardhan, News & Research WriterPublished September 28, 2026 · 8 min readReviewed by Aarav Vardhan, Editor-in-Chief

A line chart plots creative achievement against IQ score. The classic threshold claim draws a flat line above IQ 120. The largest meta-analysis instead finds a similar, modest correlation below and above 120, with no significant break at that point.

Creativity and IQ correlate only weakly, and not in the way the famous threshold theory claims. Are creative people more intelligent? Only slightly. That theory says intelligence and creativity correlate up to about IQ 120, then the link flattens out completely. The largest meta-analysis ever run on the question, pooling 447 correlations from 45,880 people, found a correlation of about .17 overall and no significant difference between the below-120 and above-120 groups — its author concluded plainly that “this study does not support threshold theory.” This guide covers where the threshold idea came from, what the two largest meta-analyses actually found, a more recent study that found the breakpoint moves depending on how creativity is measured, and what the field’s most famous creativity-test follow-up study found instead.

The classic claim: intelligence and creativity correlate below about IQ 120; above it, no further relationship (Guilford, 1950; Getzels and Jackson, 1962).
The largest test of it: a 2005 meta-analysis of 45,880 people found a weighted mean correlation of .174, with no significant difference above versus below IQ 120.
A 2021 update, correcting for measurement error: 34,610 people, overall correlation .25 — still modest, not the strong link pop psychology sometimes implies.
Creative-test scores predicted personal achievement, not public achievement, in a 50-year follow-up of Torrance Test takers; public creative achievement needed high scores on both creativity and intelligence.

Where the threshold theory came from

J.P. Guilford’s 1950 address to the American Psychological Association, titled simply “Creativity,” argued that standard intelligence tests miss an entire class of abilities: divergent thinking, the capacity to generate many different valid responses to an open-ended problem, rather than converge on the one correct answer an IQ test rewards. Getzels and Jackson followed in 1962 with Creativity and Intelligence: Explorations with Gifted Students, comparing high-IQ and high-creativity groups of students and finding they overlapped only partly. Out of that era came the threshold claim, credited across the literature to Barron (1961), Getzels and Jackson (1962), Guilford himself (1967) and MacKinnon (1962): below roughly IQ 120, a certain amount of intelligence is needed to be creative, so the two correlate; above it, intelligence stops being the limiting factor and the correlation should flatten toward zero.

It is one of the most widely repeated claims in popular writing about intelligence and creativity. It is also, on the best current evidence, not well supported as a hard cutoff.

The largest test of the threshold claim found no threshold

Kyung Hee Kim’s 2005 meta-analysis, “Can Only Intelligent People Be Creative?”, pooled 447 correlation coefficients from 21 studies published between 1961 and 2004, covering 45,880 people. The overall weighted mean correlation between intelligence and creativity was .174 (95% confidence interval .165 to .183) — positive, but modest.

Kim (2005): IQ-creativity correlation by IQ band
IQ band	Correlation (r)	Number of coefficients
Below 100	.260	part of 65 below-120
100 to 120	.140	part of 65 below-120
120 to 135	.259	part of 14 above-120
Above 135	-.215	only 2 coefficients, unreliable
All below IQ 120	.201	65 coefficients
All above IQ 120	.235	14 coefficients

If the threshold theory were right, the correlation above 120 should collapse toward zero. Instead it was slightly higher than below 120, and the difference was not statistically significant (chi-square 2.004, p = .157). Adding an IQ-120 threshold term to a regression model did not improve how well it fit the data. Kim’s own conclusion, in her words: “This study does not support threshold theory.” A narrower look at just the Torrance Tests of Creative Thinking, covered below, gave a similar mean correlation of .218 across 18 coefficients.

A 2021 update: a somewhat stronger link, still not a threshold

A 2021 update by Gerwig and colleagues in the Journal of Intelligence pooled a larger and more recent set of studies: 849 correlations from 112 studies and 34,610 people, and reported an overall correlation of .25 (95% confidence interval .21 to .30) between intelligence and divergent-thinking scores. That is noticeably higher than Kim’s .174, but the gap is mostly statistical rather than a real change over time: once the newer studies are restricted to the same uncorrected method Kim used, the estimate drops to about .19, close to her figure. The higher headline number in the 2021 study comes mainly from correcting for measurement unreliability in the tests themselves, a standard meta-analytic adjustment, not from creativity and intelligence having grown more closely linked.

A moving breakpoint, not a fixed one

Not every study agrees the relationship is perfectly flat throughout. A widely cited re-analysis by Jauk, Benedek, Dunst and Neubauer, published in Intelligence in 2013, used a statistical technique that finds a breakpoint in the data rather than assuming one at 120. It reported that where the breakpoint falls depends on how strictly creativity is defined: for a simple count of how many ideas someone can generate, the breakpoint sat far lower, around IQ 85; for a demanding measure of genuinely original ideas, it moved up toward roughly 120. In other words, a fixed threshold at 120 may be an artefact of which creativity measure a study happens to use, not a single biological cutoff. The broader pattern across both meta-analyses and this re-analysis is the same: a real but modest link that behaves differently depending on how “creative” is defined and measured, not a clean switch that turns off at a specific score.

Is creativity even part of intelligence?

Part of the disagreement is definitional. Robert Sternberg’s triarchic theory of intelligence names “creative intelligence” — the ability to deal with novelty and generate new ideas — as one of three components, alongside analytical and practical intelligence, arguing standard IQ tests mostly capture only the analytical piece. The Cattell-Horn-Carroll (CHC) model behind most modern IQ tests, by contrast, does not name creativity as one of its broad abilities at all; the closest fit is Glr, long-term storage and retrieval, which covers the kind of fluent, associative idea generation that divergent-thinking tests measure. Our guide to Gardner’s multiple intelligences covers a separate, and more famous, argument that standard IQ tests miss entire categories of ability; see also is intelligence limited to IQ.

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What the most famous creativity-test follow-up study actually found

E. Paul Torrance built the Torrance Tests of Creative Thinking (TTCT) in the 1960s to score fluency, flexibility, originality and elaboration on open-ended tasks, and then tracked his test-takers for decades. A 40-year follow-up (Cramond and colleagues, 2005) and a 50-year follow-up (Runco and colleagues, 2010) both looked at how well childhood TTCT scores predicted adult creative achievement. The finding is more precise than the popular version of the story: TTCT scores moderately predicted personal achievement (creative accomplishments in an individual’s own life and work), but predicting public achievement (creative work recognised publicly) needed an interaction between creativity and intelligence scores together. Neither measure alone told the fuller story; the combination did.

What this means if you are trying to identify creative potential

A single IQ score was never built to certify creativity, and a single creativity-test score is not a substitute for one either. Programmes that identify gifted children using only an IQ cutoff can miss students whose strength shows up in open-ended, divergent tasks rather than the convergent, single-right-answer format most IQ subtests use; the Torrance follow-ups suggest the reverse is also true, since public achievement took both kinds of ability together. Neither score alone settles the question of who is creative, and a modest .17 to .25 correlation leaves most of the variation in creativity unexplained by IQ in either direction. For another surprising trait people have tried to link to intelligence, with a very different causal story, see our guide to myopia and IQ.

Quick answers

Are highly intelligent people more creative? Only slightly. The two largest meta-analyses put the correlation at about .17 to .25, positive but modest.
Is there really an IQ 120 cutoff where the link disappears? The best-supported answer is no. The largest meta-analysis (45,880 people) found no significant difference in the correlation above versus below IQ 120.
Can someone with an average IQ be highly creative? Yes. The correlation is far from perfect in either band, and one re-analysis put the breakpoint for basic idea-generation as low as IQ 85.
Does a high IQ guarantee creativity? No. Correlations around .2 to .25 mean intelligence explains only a small share of the differences between people in creative-test scores.
Is creativity part of IQ? Not in the CHC model most modern IQ tests are built on. Sternberg’s triarchic theory treats it as a separate kind of intelligence; most IQ tests measure mainly the analytical kind.

The bottom line

The tidy version of the threshold theory — strong link below IQ 120, none above — does not hold up against the largest evidence. What holds up instead is a real but modest correlation, roughly .17 to .25, that does not flatten sharply at any single score, though where it is strongest can shift with how strictly a study defines “creative.” A high IQ makes highly creative output somewhat more likely, but the Torrance follow-ups suggest that publicly recognised creative achievement is better predicted by intelligence and creativity acting together than by either score alone.

Sources

Guilford, J.P. (1950): Creativity, American Psychologist, 5, 444-454.
Getzels, J.W. and Jackson, P.W. (1962): Creativity and Intelligence: Explorations with Gifted Students. Wiley.
Kim, K.H. (2005): Can only intelligent people be creative? A meta-analysis, Journal of Secondary Gifted Education, 16(2/3), 57-66.
Gerwig, A. et al. (2021): The relationship between intelligence and divergent thinking, a meta-analytic update, Journal of Intelligence, 9(2), 23.
Jauk, E., Benedek, M., Dunst, B. and Neubauer, A.C. (2013): The relationship between intelligence and creativity, new support for the threshold hypothesis by means of empirical breakpoint detection, Intelligence, 41(4), 212-221.
Runco, M.A., Millar, G., Acar, S. and Cramond, B. (2010): Torrance Tests of Creative Thinking as predictors of personal and public achievement, a fifty-year follow-up, Creativity Research Journal, 22(4), 361-368.
Cramond, B., Matthews-Morgan, J., Bandalos, D. and Zuo, L. (2005): A report on the 40-year follow-up of the Torrance Tests of Creative Thinking, Gifted Child Quarterly, 49(4), 283-291.
Sternberg, R.J. (1988): The Triarchic Mind: A New Theory of Human Intelligence. Viking Press.

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Diagram of the positive manifold: a correlation grid showing that verbal, spatial, numerical and memory tests all correlate positively with one another, which is the finding multiple intelligences theory predicts should not appear

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Myopia and IQ

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Myopia and IQ

Posted on September 28, 2026September 28, 2026 by Mahesh

Research & Evidence

Myopia and IQ: Are Nearsighted People Really Smarter?

By Arjun Vardhan, News & Research WriterPublished September 28, 2026 · 7 min readReviewed by Aarav Vardhan, Editor-in-Chief

A diagram shows two arrows between education and myopia. A Mendelian-randomisation study found a causal arrow from more years of education to more myopia, about a quarter of a diopter per year, but found no significant effect running the other way, from myopia to educational attainment.

The link between myopia and IQ is real: people who are nearsighted (myopic) score a few points higher on intelligence tests and complete more years of education, on average, than people with normal vision — a finding repeated in large studies since the 1980s. It does not mean blurry distance vision makes anyone smarter. The best current evidence, a 2018 genetic study of nearly 68,000 people, found the arrow points the other way: more years spent in education causally increases the odds of becoming myopic, most likely through more reading and near-work and less time outdoors, while myopia itself showed no significant effect on educational attainment. This guide covers the historical studies behind the myopia-IQ link, the genetic evidence for what actually causes what, why time outdoors matters, and why the world is getting more nearsighted.

The correlation is real. Large military-conscript studies from the 1980s found nearsighted young men scored higher on intelligence tests than their normally-sighted peers.
The likely cause runs backward from the popular story. A 2018 Mendelian-randomisation study found each extra year of education raises myopia risk (about −0.27 dioptres per year), with no significant reverse effect of myopia on education.
Time outdoors helps. A randomised trial in China cut childhood myopia by roughly a quarter just by adding one outdoor class period a day.
Myopia is becoming much more common worldwide, projected to affect around half the global population by 2050, up from about 28% in 2010.

The correlation: where the myopia-IQ link comes from

The association between nearsightedness and cognitive test performance is not a fringe claim; it goes back to large studies of military conscripts, who in some countries take both a vision exam and an intelligence test as part of the same screening. A review of this literature in the Journal of Ophthalmology (Verma and Verma, 2015) describes two of the largest: a study of 15,834 Danish conscripts found myopic men scored higher on intelligence testing than non-myopic men, a difference the review reports as roughly 7 IQ points; a study of 157,748 Israeli conscripts aged 17 to 19 found myopia associated with both higher test scores and more years of education, and the association strengthened with the severity of the myopia. Both are observational studies of young men from a specific era and testing system, not a random sample of everyone, so treat the exact point differences as illustrative rather than universal.

Two explanations, and a decisive way to tell them apart

Two explanations for the correlation have competed for decades. One is behavioural: children who read more and spend more time on close-up schoolwork are exposed to more near-work, which is a known myopia risk factor, and are also the children most likely to do well on a cognitive test — near-work would then be a common cause of both, not evidence that either one causes the other. The other is genetic: an older study by Cohn, Cohn and Jensen (1988) compared gifted children with their own non-gifted siblings and found significantly more myopia in the gifted group, which the authors read as evidence of shared genetics (pleiotropy) rather than shared behaviour. More recent genome-wide association work from the CREAM Consortium has found genetic loci where refractive error interacts with educational attainment, evidence that at least part of the story does run through shared genes, alongside the behavioural path.

A study cannot easily tell these two explanations apart with correlation alone, which is why the 2018 study below matters: it used genetics to test the direction of causation directly, rather than just the existence of a link.

What a 2018 genetic study found: education causes myopia, not the other way around

Mountjoy and colleagues, publishing in The BMJ in 2018, used data from 67,798 UK Biobank participants and a technique called Mendelian randomisation, which uses genetic variants linked to a trait as a kind of natural experiment to test which way a causal arrow points. Their result: each additional year of education increased myopic refractive error by about 0.27 dioptres (95% confidence interval 0.17 to 0.37, a very strong statistical result). Tested in the other direction, each additional dioptre of myopia was associated with just 0.008 fewer years of education, a result with a confidence interval crossing zero and not statistically significant. The authors’ own conclusion was direct: more time in education is a causal risk factor for myopia. Myopia causing more education was not supported.

Mountjoy et al. (2018), Mendelian randomisation between education and myopia
Direction tested	Effect	Statistical significance
More education, then myopia	-0.27 D per year of education (95% CI -0.37 to -0.17)	Highly significant (P = 4×10 -8)
More myopia, then education	-0.008 years of education per dioptre (95% CI -0.041 to 0.025)	Not significant (P = 0.6)

That is the opposite emphasis from how the finding often gets repeated. The honest reading is not “nearsighted people are smarter” but “people who spend longer in education are more likely to become nearsighted,” with no good evidence running the other way. See also our guides to is IQ genetic and eye colour and IQ for two other traits people have tried to link to intelligence, with very different results.

Why time outdoors matters

If near-work is the behavioural link, then time spent away from close-up tasks should help, and a randomised trial backs that up directly. He and colleagues, publishing in JAMA in 2015, added one 40-minute outdoor class period per day to the school schedule of first-graders in 12 schools in Guangzhou, China, for three years, against 12 comparison schools with no change. Myopia had developed in 30.4% of the intervention group by the end of the study, against 39.5% of the comparison group, a roughly one-quarter reduction in new cases from one extra outdoor period a day. Nothing in that result requires less studying, only more time outdoors alongside it, which is consistent with light exposure, not merely a break from books, being the protective factor most researchers now point to.

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A fast-rising, worldwide trend

Myopia has been becoming more common for decades, and the trend line is steep. A widely cited 2016 analysis in Ophthalmology (Holden and colleagues) estimated that myopia affected about 28% of the world’s population, roughly 2 billion people, in 2010, and projected that share to reach roughly 50%, about 4.8 billion people, by 2050. High myopia, the more severe form that carries greater risk of other eye conditions, was estimated at about 4% (227 million people) in 2010, projected to reach roughly 10% (938 million) by 2050. More schooling, more screen-based near-work and less unstructured outdoor time in childhood are the leading explanations researchers give for the trend, which fits the causal direction the 2018 genetic study found.

A different but equally surprising IQ correlate

Myopia is not the only ordinary trait people have tried to link to intelligence. Our guide to creativity and IQ covers another one, the long-debated claim that intelligence and creative ability stop correlating above a certain score — a claim that, like the myopia story, turns out to be less clean than the popular version once you check the largest studies.

Quick answers

Are nearsighted people smarter? They score a few points higher on cognitive tests on average in several large studies, but the best evidence says this is not because myopia causes higher intelligence.
Does myopia cause high IQ, or does high IQ cause myopia? Neither, precisely. The strongest causal evidence says more years of education causally increases myopia risk; it found no significant effect of myopia on educational attainment.
Why are nearsighted people associated with higher test scores? Likely because more reading and near-work, both a myopia risk factor and a habit common among high scorers, plus some shared genetic factors, sit behind both.
Does reading more cause myopia? Extended near-work is one established risk factor; reduced time outdoors is another, and a randomised trial found extra outdoor time reduced new cases by roughly a quarter.
Is myopia becoming more common? Yes. A 2016 projection put it at roughly 28% of the world in 2010, rising to roughly 50% by 2050.

The bottom line

Nearsighted people really do score somewhat higher on cognitive tests in several large studies, but the best causal evidence available, a 2018 genetic study of nearly 68,000 people, points from education to myopia rather than from myopia to intelligence. More time spent reading and studying, and less time outdoors, is the more likely story behind both. Protecting a child’s eyesight and supporting their education are not in tension: the same research that explains the myopia-IQ correlation is also the evidence base for encouraging outdoor time alongside schoolwork, not instead of it.

Sources

Mountjoy, E. et al. (2018): education and myopia, assessing the direction of causality by Mendelian randomisation, The BMJ, 361:k2022.
He, M. et al. (2015): effect of time spent outdoors at school on the development of myopia among children in China, a randomised clinical trial, JAMA, 314(11):1142-1148.
Holden, B.A. et al. (2016): global prevalence of myopia and high myopia and temporal trends from 2000 through 2050, Ophthalmology, 123(5):1036-1042.
Verma, A. and Verma, A. (2015): a novel review of the evidence linking myopia and high intelligence, Journal of Ophthalmology, 2015:271746.
Cohn, S.J., Cohn, C.M. and Jensen, A.R. (1988): myopia and intelligence, a pleiotropic relationship?, Human Genetics, 80:53-58.

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PISA Test vs IQ Test

Posted on September 28, 2026September 28, 2026 by Mahesh

Understanding IQ

Is PISA an IQ Test? What PISA Actually Measures

Is PISA an IQ test? No. PISA surveys applied school literacy across whole education systems and returns no individual score, while an IQ test diagnoses one person. See the new PISA 2025 results, published September 2026, and the real debate over using PISA as a national IQ proxy.

By Alden Cross, Intelligence Research WriterPublished September 28, 2026 · 7 min readReviewed by Aarav Vardhan, Editor-in-Chief

A comparison card contrasts PISA and an individual IQ test. PISA surveys a sample of 15-year-olds in each country and school system, reports no individual score, and rotates test booklets. An IQ test is given one to one and reports one diagnostic score to the person tested.

Is PISA an IQ test? No. The Programme for International Student Assessment, run by the OECD, measures how well 15-year-olds can apply reading, maths and science knowledge to real-world problems, using a survey design that never even returns an individual score to the student who sat it. An IQ test, by contrast, is given one to one and produces exactly that: one person’s diagnostic score. The two are correlated at the level of whole countries, but that correlation itself has been strongly challenged. This guide covers what PISA actually measures, the September 2026 results from the newest cycle, how it differs structurally from an IQ test, and the real debate over using PISA scores as a stand-in for national IQ.

What PISA measures: applied reading, maths and science literacy in 15-year-olds, not general cognitive ability.
No individual score: PISA uses rotated test booklets and reports statistical estimates for a population, not a score for any one student.
Newest results: PISA 2025, published September 2026, covered about 91 countries and education systems and recorded the lowest OECD-average scores yet in all three subjects.
The IQ link is contested: national PISA averages correlate strongly with one controversial “national IQ” dataset, but that dataset’s sampling has been heavily criticised.

What PISA actually is

PISA stands for the Programme for International Student Assessment. The OECD has run it since 1997, first administering it in 2000 and repeating it roughly every three years since (the 2022 round was delayed a year by the pandemic; the OECD is moving to a four-year cycle after 2025). In its own words, “PISA is a regularly-conducted survey of 15-year-old students around the world that assesses the extent to which they have acquired key knowledge and skills essential for full participation in social and economic life,” and it deliberately goes beyond recall: it “assess[es] how well students can extrapolate from what they have learned… and apply it to real-life problems.” That is an applied-literacy test tied to what 15-year-olds have been taught and have practised, not a culture-fair test of general reasoning ability like the ones covered in our guide to professional IQ tests. A different group-administered school test, the OLSAT, blurs the line with an IQ test more than PISA does; see our guide to the OLSAT test.

The September 2026 results: PISA 2025

The newest cycle, PISA 2025, covered 15-year-olds across 38 OECD countries and 53 partner countries and economies, about 91 education systems in total, with initial results published by the OECD in September 2026. On the programme’s shared scale, where each subject was originally set to a mean of 500 with a standard deviation of 100 in its baseline year, the 2025 OECD average came to 482 in science, 461 in reading and 463 in mathematics. All three fell from the 2022 cycle (science down 3 points, not a significant change; reading down 14; mathematics down 9), which the OECD describes as the lowest OECD-average performance recorded so far in all three core subjects.

PISA 2025 OECD averages and change since PISA 2022
Subject	2025 OECD average	Change since 2022
Mathematics	463	-9 points
Reading	461	-14 points
Science	482	-3 points, not significant

The highest scores in the 2025 cycle came from the Chinese provinces tested as a group under the label B-S-J-Z (Beijing, Shanghai, Jiangsu and Zhejiang), which led in both mathematics (612) and science (597), and from Singapore, which led in reading (535) and also scored highly in science (560) and mathematics (563). Macao, Chinese Taipei, Japan and Korea also placed near the top across subjects. Bear in mind that B-S-J-Z represents specific, more developed Chinese provinces rather than the country as a whole, a distinction the OECD itself is explicit about.

Why PISA does not work like an IQ test

The structural differences run deeper than subject matter. PISA uses a rotated-booklet design: no single student answers every question, and item response theory combines everyone in a school or country into population-level statistical estimates (“plausible values”) rather than individual scores. The programme’s own technical documentation is explicit that PISA is low-stakes for the student: results are used to compare education systems, and students taking it do not receive individual feedback on their own performance at all. An individually administered test such as the Stanford-Binet or the Wechsler Intelligence Scale for Children works the opposite way: one person sits with a trained psychologist for roughly 45 to 65 minutes and receives a Full Scale IQ plus several index scores, a diagnostic result meant to describe that individual. PISA was never built to produce that kind of number for anyone.

PISA versus an individually administered IQ test
Feature	PISA	Individual IQ test (e.g. WISC-V)
Purpose	Compare education systems across countries	Diagnose one person’s cognitive profile
Administration	Group, rotated booklets, often computer-based	One to one with a trained examiner
Individual score returned?	No, only population-level estimates	Yes, a Full Scale IQ plus index scores
What it targets	Applied reading, maths and science literacy tied to schooling	General reasoning ability, designed to reduce dependence on curriculum content
Stakes for the student	Low; no individual feedback given	High; used for diagnosis, placement or eligibility

The real debate: do national PISA scores measure "national IQ"?

National average PISA scores correlate strongly with one specific dataset of estimated national IQs: Rindermann (2007) reported a correlation of .88 (adjusted to .84) between a combined student-assessment score, PISA included, and the national IQ estimates published by Lynn and Vanhanen (2006) across 46 to 47 countries. That is a strong correlation, and it is often cited as evidence that PISA is, in effect, measuring the same thing an IQ test would. The trouble is the national IQ dataset itself. Volken (2003) found the underlying samples were not representative at the national level for many countries, and a systematic review by Wicherts, Dolan and van der Maas (2010) found the exclusion criteria used to build the Lynn and Vanhanen estimates were never published; when they added back studies that had been excluded without a stated reason, the estimated average IQ for sub-Saharan Africa rose from 67 to 82, a very large change driven entirely by which studies were counted. Our own page on average IQ by country publishes figures from this same contested tradition, and our news piece on what country IQ rankings data cannot support sets out the wider case against treating any national IQ ranking as settled science. A strong country-level correlation between two measurements does not make them interchangeable, especially when one side of the correlation is itself disputed.

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What about one person? Does a PISA-style score predict an individual IQ score?

At the level of one student rather than one country, the relevant comparison is the long-studied link between intelligence and school achievement generally. A large meta-analysis by Roth and colleagues (2015), pooling 240 samples and 105,185 people, found intelligence correlated with school grades at ρ = .54. Earlier meta-analyses looking specifically at standardised achievement tests, the closer comparison to what PISA measures, found correlations in a similar range: .48 (Boulanger, 1981), .43 (Fleming and Malone, 1983) and .34 (Steinkamp and Maehr, 1983). No peer-reviewed study was found that measured the correlation between an individual PISA-style assessment score and an individual IQ score directly, so the honest answer is that the relationship is inferred from the broader achievement-intelligence literature, not measured on PISA itself.

Quick answers

Is PISA an IQ test? No. It is an applied-literacy assessment of reading, maths and science for 15-year-olds, built to compare education systems, and it does not return an individual score to any student.
What is the most recent PISA result? PISA 2025, published by the OECD in September 2026: OECD averages of 463 in mathematics, 461 in reading and 482 in science, the lowest recorded so far in all three.
Which country scored highest on PISA 2025? B-S-J-Z (Beijing, Shanghai, Jiangsu and Zhejiang, in China) led mathematics and science; Singapore led reading.
Do PISA scores measure national IQ? They correlate strongly with one specific, heavily disputed national-IQ dataset. The correlation is real; whether that dataset is trustworthy is a separate and contested question.
Can a school or a parent get an individual child’s PISA score? No. PISA is designed as a population survey and does not report individual results at all.

The bottom line

PISA and an IQ test measure different things in different ways for different purposes: PISA surveys applied school-taught literacy across whole education systems and tells a student nothing about their own score, while an IQ test diagnoses one person’s general reasoning ability. The two are related at the national level, strongly enough that some researchers treat PISA as a proxy for national cognitive ability, but that proxy rests on a national-IQ dataset whose sampling methods critics have directly challenged. Read PISA rankings for what they are, a measure of applied literacy under a specific school system, rather than as a national intelligence test.

Sources

OECD (2026): PISA 2025 Results (Volume I).
US National Center for Education Statistics: PISA technical notes on scoring and plausible values.
Rindermann, H. (2007): the g-factor of international cognitive ability comparisons, European Journal of Personality, 21:667-706.
Volken, T. (2003): IQ and the wealth of nations, a critique of Richard Lynn and Tatu Vanhanen’s recent book, European Sociological Review, 19(4):411-412.
Wicherts, J.M., Dolan, C.V. and van der Maas, H.L.J. (2010): a systematic literature review of the average IQ of sub-Saharan Africans, Intelligence, 38:1-20.
Roth, B. et al. (2015): intelligence and school grades, a meta-analysis, Intelligence, 53:118-137.

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A single card shows the OLSAT at a glance: seven levels, A through G, spanning kindergarten through grade 12, five reasoning clusters, and a School Ability Index scaled to a mean of 100 and a standard deviation of 16, wider than the Wechsler and Stanford-Binet 5 scale of 15.

Scores & Scales

OLSAT Test

The OLSAT test (Otis-Lennon School Ability Test) is a group-administered reasoning test scored on a School Ability Index with mean 100 and SD 16, best known for New York City Gifted and Talented admissions. See how it works, its history, and the NYC admissions cutoffs and controversy.

September 28, 20268 min read

Understanding IQ

Is Intelligence limited to IQ?

March 28, 20245 min read

Research & Evidence

Cultural Bias in IQ Tests

Ask whether IQ tests are culturally biased and you get two confident, opposite answers. Both are partly right, because the word means something far narrower to a psychometrician than it does in ordinary use. Here is what the item-level evidence shows, and where culture really does get into a score.

August 31, 20267 min read