Height and IQ are weakly linked: a correlation of about 0.16 means someone 7 cm taller scores about 2 IQ points higher on average, too little to matter.
Dr. Russell T. WarneChief Scientist
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Taller people do score slightly higher on IQ tests on average, but the link is weak. In a Scottish study of 6,815 adults, the correlation between height and general intelligence was 0.16, which works out to roughly 2 IQ points for every 7 cm of extra height, far too small to tell you anything useful about one person.
That correlation has turned up in study after study, in children as well as adults and on several continents. The more interesting questions are why it exists and whether growing taller could make anyone smarter. This page covers how big the association is, what genetic and environmental explanations researchers have tested, and which confounds make the raw numbers easy to misread.
How strong is the link between height and IQ?
Height and IQ are consistently correlated at about 0.10 to 0.20, according to a review of earlier work by Matthew Keller and colleagues in PLoS Genetics. The cleanest single estimate comes from Generation Scotland, where Riccardo Marioni and colleagues found an age- and sex-adjusted correlation of 0.16 between height and a general intelligence factor built from four cognitive tests.
To turn that into IQ points, multiply the correlation by the IQ standard deviation (15 points) to get the expected IQ difference for each standard deviation of height. In Generation Scotland, the standard deviation of height was 7 cm in both men and women, so:
• Per 7 cm of height: 0.16 × 15 = about 2.4 IQ points on average.
• Per centimetre: about a third of an IQ point.
• Variance explained: 0.16 squared is 0.026, so height accounts for under 3% of the differences in IQ between people.
The gap looks larger at the extremes. Torsten Tuvemo and colleagues studied 32,887 healthy 18-year-old Swedish conscripts, after excluding men with growth-affecting disorders. The shortest men (at least two standard deviations below average height) had a mean score of 4.22 on the army's 1-to-9 "standard nine" intellectual performance scale, against 5.17 for everyone else. A standard nine scale has a mean of 5 and a standard deviation of about 2, so that gap is roughly half a standard deviation, or about 7 IQ points, and the short men's average still sat close to the middle of the scale.
The association starts early. In a US and UK analysis, economists Anne Case and Christina Paxson reported that taller children perform better on cognitive tests from as early as age 3, before schooling has had a chance to play a role.
Why taller people score higher: genes and assortative mating
The best evidence points to genetic overlap as the main explanation in wealthy countries today. Marioni's team used DNA data from unrelated people and estimated a genetic correlation of 0.28 between height and intelligence. Their bivariate heritability estimate was 0.71, meaning that most of the observed correlation was explained by shared genetic influences.
There are two ways genes for height and genes for IQ could end up correlated. The same genes could affect both traits, which geneticists call pleiotropy. Or people could choose partners in a way that pairs tall with clever. Keller's team tested this using 7,905 twins, siblings and parents from Australian and US samples. They found that people choose partners who resemble them on both traits, and across traits: women's IQ correlated 0.18 with their partners' height, and men's IQ correlated 0.11 with their partners' height. Over generations, that kind of mate choice bundles height-raising and IQ-raising gene variants together in the same children. After modelling this, the authors concluded that the height–IQ correlation was almost entirely genetic, with pleiotropy and assortative mating contributing about equally.
A Dutch twin study by Karri Silventoinen and colleagues, following twins from age 5 into middle age, also attributed the correlations it found to genetic factors. For more on what twin and DNA studies can and cannot say about intelligence in general, see our article on whether genes are important for determining intelligence.
The case for childhood environment
Not every study agrees. Jon Martin Sundet and colleagues matched Norwegian army records with twin registries for nearly 2,600 male twin pairs. In their analysis, correlated shared environments accounted for 59% of the height–IQ correlation, with genes accounting for 35%. Shared environment means the conditions twins grow up in together, such as family income, diet and illness in childhood.
That explanation makes biological sense. In five long-running birth cohorts from Brazil, Guatemala, India, the Philippines and South Africa, Cesar Victora and colleagues found that undernutrition in early childhood was strongly associated with both shorter adult height and less schooling. Our article on whether diet or nutrition affects IQ covers the wider evidence. The environmental contribution is likely to be larger where childhood deprivation is common and smaller in wealthy countries where most children are well fed, which may explain why studies from different places and decades disagree.
Population trends point the same way. The NCD Risk Factor Collaboration pooled height measurements from 18.6 million people born between 1896 and 1996 and found large gains in many countries; South Korean women, for example, became 20.2 cm taller over the century. Average IQ scores rose over much of the same period, a pattern known as the Flynn effect, and better nutrition and health are among the explanations proposed for both trends.
Does being taller make you smarter?
No good evidence says that height itself raises intelligence. The strongest test comes from a 2022 study in Nature Genetics by Laurence Howe and colleagues, which pooled genetic data from 178,086 siblings. Using a method called Mendelian randomisation, which treats inherited height variants as a natural experiment, they estimated that a genetic tendency toward one standard deviation more height went with 0.07 standard deviations higher cognitive ability, about 1 IQ point. When the analysis was repeated within sibling pairs, the estimate was 0.05, with a confidence interval running down to zero.
That within-family comparison matters because siblings share parents, so differences between them cannot come from family background or from parental mate choice. A small effect may survive, possibly reflecting general health during growth, but it is a fraction of the already small raw correlation.
Height does predict some life outcomes beyond what IQ explains. In a Swedish cohort of more than 950,000 men measured at 18, Patrik Magnusson and colleagues found that each extra 5 cm of height raised the odds of higher education by about 10%, even after adjusting for cognitive ability and parental background. The link held between full brothers (odds ratio 1.08).
Why the "tall people are smarter" idea spreads
Part of the appeal is the well-known height premium in pay. Case and Paxson argued that this premium is explained by childhood cognitive scores, with taller adults selecting into jobs that demand more verbal and numerical skill. That finding is often summarised as "tall people are smarter", which overstates a correlation of 0.16.
Several confounds can inflate the raw numbers:
• Sex: in Generation Scotland, men averaged 176 cm and women 162 cm, so pooling the sexes without adjustment lets any sex difference in test scores create or hide a height correlation. That estimate was adjusted for sex and age.
• Age and birth cohort: older generations are shorter on average, and test scores also change with age and birth year, so samples spanning many ages need age adjustment.
• Socioeconomic status: family income affects both childhood growth and educational opportunity, which is why within-family designs give the most trustworthy estimates.
None of this justifies judging anyone by their height. With a correlation of 0.16, the IQ distributions of short and tall people overlap almost completely, and plenty of short people score far above plenty of tall ones. If a child's growth is a concern, that is a question for a paediatrician; it says nothing about the child's intelligence.
Frequently asked questions
Are taller people smarter?
On average, very slightly. The correlation is about 0.10 to 0.20, worth roughly 2 IQ points per 7 cm of height, which is too small to predict any individual's IQ.
How many IQ points is one inch of height worth?
Using the Generation Scotland correlation of 0.16 and a height standard deviation of 7 cm, one inch (2.54 cm) corresponds to slightly less than 1 IQ point on average.
Does being short mean you have a lower IQ?
No. Very short men in a Swedish conscript study averaged about 7 points lower, but their average was still near the middle of the scale, and the IQ distributions of short and tall people overlap almost entirely.
Is the link between height and IQ genetic?
Mostly, in recent studies from wealthy countries. DNA and family studies attribute most of the correlation to shared genetic influences and to people choosing partners similar on both traits, though one large Norwegian twin study gave a bigger role to childhood environment.
Will growing taller raise my IQ?
There is no evidence that it would. Within-sibling genetic analyses suggest any direct effect of height on cognitive ability is close to zero.
The takeaway
The link between height and IQ is real, consistent and small: about 2 IQ points for every 7 cm, with under 3% of IQ differences explained by height. Most of it appears to reflect gene variants that travel together because of shared genetic influences and partner choice, with childhood nutrition and health also playing a part in some populations. Height tells you very little about how well someone reasons, while an online IQ test built by psychometricians measures it directly.
References
1. Marioni, R. E., Batty, G. D., Hayward, C., Kerr, S. M., Campbell, A., Hocking, L. J., Generation Scotland, Porteous, D. J., Visscher, P. M., & Deary, I. J. (2014). Common genetic variants explain the majority of the correlation between height and intelligence: The Generation Scotland study. Behavior Genetics, 44(2), 91-96. doi.org
2. Keller, M. C., Garver-Apgar, C. E., Wright, M. J., Martin, N. G., Corley, R. P., Stallings, M. C., Hewitt, J. K., & Zietsch, B. P. (2013). The genetic correlation between height and IQ: Shared genes or assortative mating? PLoS Genetics, 9(4), e1003451. doi.org
3. Tuvemo, T., Jonsson, B., & Persson, I. (1999). Intellectual and physical performance and morbidity in relation to height in a cohort of 18-year-old Swedish conscripts. Hormone Research, 52(4), 186-191. doi.org
4. Case, A., & Paxson, C. (2008). Stature and status: Height, ability, and labor market outcomes. Journal of Political Economy, 116(3), 499-532. doi.org
5. Silventoinen, K., Posthuma, D., van Beijsterveldt, T., Bartels, M., & Boomsma, D. I. (2006). Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age. Genes, Brain and Behavior, 5(8), 585-595. doi.org
6. Sundet, J. M., Tambs, K., Harris, J. R., Magnus, P., & Torjussen, T. M. (2005). Resolving the genetic and environmental sources of the correlation between height and intelligence: A study of nearly 2600 Norwegian male twin pairs. Twin Research and Human Genetics, 8(4), 307-311. doi.org
7. Victora, C. G., Adair, L., Fall, C., Hallal, P. C., Martorell, R., Richter, L., & Sachdev, H. S. (2008). Maternal and child undernutrition: Consequences for adult health and human capital. The Lancet, 371(9609), 340-357. doi.org
8. NCD Risk Factor Collaboration (NCD-RisC). (2016). A century of trends in adult human height. eLife, 5, e13410. doi.org
9. Howe, L. J., Nivard, M. G., Morris, T. T., Hansen, A. F., Rasheed, H., Cho, Y., ... Davies, N. M. (2022). Within-sibship genome-wide association analyses decrease bias in estimates of direct genetic effects. Nature Genetics, 54(5), 581-592. doi.org
10. Magnusson, P. K. E., Rasmussen, F., & Gyllensten, U. B. (2006). Height at age 18 years is a strong predictor of attained education later in life: Cohort study of over 950,000 Swedish men. International Journal of Epidemiology, 35(3), 658-663. doi.org
Hero image: Coiled tape measure, by Pink Sherbet Photography from USA, CC BY 2.0. Via Wikimedia Commons.
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