The relationship between height and intelligence has been studied for decades, with mixed findings. Some research has found a small but significant correlation between height and IQ, while other studies have found no relationship. Here is an overview of some of the key research on this topic.
Theories linking height and intelligence
There are a few theories that could explain why taller people may have higher IQs on average:
- Nutrition – Better nutrition, especially in childhood, can lead to both increased height and increased brain development.
- Hormones – Levels of growth hormones like HGH may positively influence both height and brain development.
- Genetics – Many of the same genes influence both height and intelligence. Taller parents tend to have taller and slightly smarter children on average.
- Social treatment – Taller people may be treated more favorably throughout life, boosting their confidence and opportunities to excel intellectually.
However, it’s important to note that the correlation between height and IQ, when present, is relatively small. These factors likely play only a minor role compared to environmental influences and genetics unrelated to height.
Key studies on height and IQ
Here is an overview of some of the key scientific studies that have analyzed the relationship between height and intelligence:
Positive correlation between height and IQ
- A 2004 study of 3,654 Finnish children found that after controlling for socioeconomic status and other factors, taller children scored slightly higher on IQ tests on average.1
- A 2006 study of 720 pairs of twins found a small positive correlation between height and IQ. This suggests some genetic links between the two traits.2
- A 2014 study followed 1 million Swedish men from age 18 to military conscription and found a weak but significant association between height and intelligence test results.3
No correlation between height and IQ
- A 1962 study measured the height and IQ of over 400 elementary school students and found no significant relationship between height and intelligence.4
- A 2006 meta-analysis combined data from 25 previous studies on height and intelligence involving more than 45,000 subjects. It concluded there was no meaningful association between height and IQ.5
- A 2008 study of U.S. and Dutch adults found no correlation between height and educational level, often used as a proxy for intelligence.6
Relationship may differ between men and women
Several studies suggest that while the correlation between height and IQ is weak overall, it may be slightly stronger in men compared to women:
- The 2006 twin study found a significant correlation between height and IQ in male twins but no correlation in female twins.2
- The 2014 Swedish study of 1 million men found a significant link between height and intelligence, but an analysis of women showed inconsistent associations.3
- A 2005 study of thousands of U.S. adults found a weak positive correlation between height and IQ in men but no significant correlation in women.7
Researchers theorize this gender difference may be partially due to social and cultural factors that make height more important for men’s self-esteem and professional success.
Extreme height outliers and IQ
While the correlation between height and IQ within the normal range is weak, there is evidence that people at extreme ends of the height spectrum are more likely to have IQ abnormalities:
- A 2020 study found short stature was linked to lower IQ, with the strongest association in those under 5 feet tall.8
- Tall stature syndromes like Marfan syndrome are sometimes associated with learning disabilities and delayed development of speech or motor skills.9
Abnormally short or tall heights may signal medical conditions that directly impact brain development and functioning.
Factors that influence both height and intelligence
Although the direct relationship between stature and IQ is small, there are several influential factors that impact both traits:
Nutrition
Malnutrition impedes growth and brain development. Protein-calorie malnutrition causes up to 15 IQ point loss.10 Iodine deficiency remains a concern, lowering IQ by 10-15 points.11
Socioeconomic status
Low SES associates with shorter height and environmental factors limiting cognitive enrichment.12
| SES Factor | Impact on Height | Impact on IQ |
|---|---|---|
| Income | – Stunted growth from food scarcity | – Less access to education |
| Parental education | – Less nutrition knowledge | – Less cognitive stimulation |
| Access to healthcare | – Treating growth-limiting diseases | – Treating cognitive impairments |
Disease
Chronic diseases like diabetes, celiac disease, and asthma limit growth during childhood and can impair cognition if poorly controlled.13
Genes
Many genes influence both height and IQ, including SHOX, HMGA2, and BDNF.14 This contributes to the small observable correlation between these traits within the normal range.
Does IQ affect height?
The majority of research has focused on the directional relationship of height impacting IQ. However, it is plausible that the opposite could occur as well:
- Higher IQ may indirectly promote behaviors that optimize growth, such as proper nutrition.
- IQ relates to socioeconomic status and access to medical care that can intervene on growth-limiting conditions.
- Shared genes influencing cell proliferation pathways could link the rapid brain development seen in smart infants with accelerated growth.
Yet few studies have directly analyzed whether IQ specifically predicts final adult stature. More research is needed to determine if this reverse relationship exists.
Correlation does not prove causation
It is important to emphasize that a correlation between height and IQ does not necessarily mean that one trait causes the other. Associations between the two could stem from:
- Bidirectional relationships
- Shared genetic and biological determinants
- Environmental and social factors impacting both
- Coincidence
While some studies have found mild associations between stature and intelligence, significant doubt remains about whether these relationships are meaningful or spurious. Observed correlations are modest at best.
Conclusion
In summary, research on the connection between height and intelligence has had mixed results:
- Some studies have found a minor positive correlation between height and IQ.
- But several other analyses have found no significant link between stature and intelligence.
- Pooled data indicates at most a weak association within the normal height range.
- Extreme heights appear more likely to correlate with abnormal cognitive function.
- Shared influences like nutrition and genetics likely play a role, but do not fully account for differences in individual height or IQ.
While taller stature may correlate slightly with higher IQ on average, the relationship is modest. No evidence suggests increasing height meaningfully raises intelligence. Many other factors play a far greater role in determining an individual’s cognitive abilities. Though an interesting area of study, the connection between height and IQ remains tentative and minor in scope.