Myths and famous claims
What was Leonardo da Vinci's IQ?
What is documented
Leonardo da Vinci never took an IQ test: he died in 1519, nearly four centuries before the first one. The numbers you see trace back to Catharine Cox’s 1926 study, which estimated him at 135 from childhood records and 150 for ages 17 to 26. They are estimates from biographies, not scores.
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Four centuries before the first IQ test
Leonardo da Vinci lived from 1452 to 1519 (Cox 1926). The first intelligence scales were developed by Alfred Binet and Theodore Simon between 1905 and 1911, so anyone who died before 1905 could never have taken one (Britannica, Alfred Binet). For Leonardo, that gap is close to four hundred years. Any number attached to him is a reconstruction from written records.
Where the numbers come from
The figures trace to Catharine Cox's 1926 study of 301 eminent historical figures, part of Lewis Terman's Genetic Studies of Genius (Simonton 2020). Cox only included people born between 1450 and 1850 whose fame was earned rather than inherited, which placed Leonardo, born in 1452, near the very start of her range. Three raters read the biographical record and gave each person two estimates.
| Cox 1926 estimate for Leonardo | Value |
|---|---|
| From childhood records | 135 |
| From records for ages 17 to 26 | 150 |
These are the raw figures in the book (Cox 1926). Cox believed they were too low. She wrote that the 135 ratings for Leonardo and Darwin were held down by thin records and that their true level was probably above 160. That reasoning is explained on the page about historical IQ estimates: when the records were thin, her raters pulled their estimates toward an average of 100.
Try one · Logical Reasoning
Which tile completes the second pair?
Tap the option you think is right, or show the answer.
Show the answer
The missing panel shows a large solid triangle pointing right on its own (option 1).
How to solve it
- Compare the first two panels and name exactly what changed.
- The whole figure turns a quarter turn counterclockwise.
- The large shape becomes solid.
- Nothing else changes.
- Apply the same changes to the third panel: a large hatched triangle pointing down on its own.
- So the missing panel shows a large solid triangle pointing right on its own.
That was 1 puzzle. The full test has 25.
Why thin records matter so much here
Cox's method needed evidence about childhood and youth: what a person did, and at what age. For someone born in the fifteenth century, that record is sparse. The same problem kept William Shakespeare out of the study entirely, because too little is recorded about his childhood and adolescence (Simonton 2020). Leonardo made it in, but with less to go on than many later figures.
What an estimate is, and is not
Cox herself warned that her corrected estimates were not meant to give exact scores for any individual (Cox 1926). Dean Keith Simonton adds that raters had to judge each person by their own field, and that a historiometric estimate is not the same thing as a test score, because a test like the Stanford-Binet samples general abilities every child is expected to develop (Simonton 2020). A painter and engineer of the Renaissance was judged on very different evidence from a modern child at a testing table.
How the estimates compare on our score pages
As positions on a modern curve with a mean of 100 and a standard deviation of 15, 135 is higher than about 99% of people and 150 higher than about 99.96%. You can see those points on IQ 135 and IQ 150. They are illustrations only, since Cox's figures are not test results.
How to judge a famous IQ claim
- Could the person have been tested? Leonardo could not.
- Does the claim name who made the estimate and by what method?
- Is the figure one the source actually printed, and is it raw or corrected?
- Does it come with the warning the original author gave?
Compare Isaac Newton and Charles Darwin, who appear in the same study.
Sources
- Cox, C. M. (1926). Genetic Studies of Genius, Vol. II: The Early Mental Traits of Three Hundred Geniuses. Stanford University Press (scan of original) gwern.net/doc/iq/high/1926-cox-theearlymentaltraitsof300geniuses.pdf
- Encyclopaedia Britannica. Alfred Binet (read via Wayback Machine, January 2025) www.britannica.com/biography/Alfred-Binet
- Simonton, D. K. (2020). Galton, Terman, Cox: The Distinctive Volume II in Genetic Studies of Genius. Gifted Child Quarterly. doi:10.1177/0016986220921360 doi.org/10.1177/0016986220921360