Myths and famous claims
What was Isaac Newton's IQ?
What is documented
Isaac Newton never took an IQ test: he died in 1727, almost two centuries before the first test in 1905. The best-known figures come from Catharine Cox’s 1926 study, which estimated him at 130 from his childhood records and 170 from his records for ages 17 to 26. Those are estimates, not scores.
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Newton lived long before IQ tests
Isaac Newton lived from 1642 to 1727 (Cox 1926). Alfred Binet and Theodore Simon developed their intelligence scales for children between 1905 and 1911, so anyone who died before 1905, Newton included, could never have taken one (Britannica, Alfred Binet). Every IQ number attached to Newton is therefore an estimate made after the fact, from written records. The history of IQ tests sets out when each kind of test appeared.
Where the numbers come from
The source behind most Newton figures is Catharine Cox's 1926 book, the second volume of Lewis Terman's Genetic Studies of Genius. Cox estimated IQs for 301 eminent people who had already died, using more than 3,000 biographical sources (Simonton 2020). Three raters, Cox, Terman and Maud Merrill, gave each person two estimates: one from childhood records and one from records for ages 17 to 26.
| Cox 1926 estimate for Newton | Value |
|---|---|
| From childhood records | 130 |
| From records for ages 17 to 26 | 170 |
These are the raw figures printed in the book (Cox 1926). Cox also produced corrected versions, because her raters pulled estimates toward 100 when records were thin. Higher Newton figures circulate online, but we have not verified a corrected number for him in the book, so we do not repeat one here.
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 outlined circle, with small solid shapes: a square at the top (option 1).
How to solve it
- Compare the first two panels and name exactly what changed.
- The main shape and the small shapes swap forms: the main shape takes the form of the small ones, and the small ones take the form of the main shape.
- Nothing else changes.
- Apply the same change to the third panel: a large outlined square, with small solid shapes: a circle at the top.
- So the missing panel shows a large outlined circle, with small solid shapes: a square at the top.
That was 1 puzzle. The full test has 25.
What a retrospective estimate is, and is not
An estimate like this is a judgment by readers of biographies about how advanced a person seemed for their age. Cox herself warned that her corrected estimates were not meant to give exact scores for any individual (Cox 1926). Dean Keith Simonton, a leading researcher in the field, points out that the Stanford-Binet measures general abilities that all children are expected to develop, so a historiometric estimate is not the same thing as a test score (Simonton 2020). He also notes that raters judged each person by their own field, and that a study run backward from fame may not match one run forward from childhood.
A 1978 reanalysis that averaged Cox's corrected estimates found a group mean of 158.9 for her whole sample (Walberg, Rasher & Hase 1978). That figure describes the group, not Newton.
How the estimates compare on our score pages
Read as positions on a modern curve with a mean of 100 and a standard deviation of 15, Cox's 130 would sit above about 97.7% of people (see IQ 130), and her 170 above about 99.9998%. Those comparisons are only illustrations: Cox worked before the deviation IQ existed, and her figures are estimates from records, not measurements.
How to judge a famous IQ claim
- Could the person have taken a test? For Newton, no.
- If it is an estimate, is the estimator named? For Newton, it is usually Cox.
- Is the number one Cox actually printed, and is it labeled raw or corrected?
- Is the childhood or the young-adult estimate being quoted?
For the full method, read how historical IQ estimates were made. The same study covers Leonardo da Vinci and Charles Darwin.
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
- Walberg, H. J., Rasher, S. P., & Hase, K. (1978). IQ Correlates With High Eminence. Gifted Child Quarterly, 22(2), 196-200. doi:10.1177/001698627802200213 doi.org/10.1177/001698627802200213