Geniuses of history on the same scale

Catharine Cox was part of Lewis Terman's team at Stanford. She read the biographies, letters and school records of about 300 historical figures, and raters estimated the IQ each one would have shown in childhood and in youth, from ages 17 to 26.

Nobody took a test. These are estimates based on what the sources reported, and Cox herself measured how reliable the data on each person was. In many cases, not very.

We show the value Cox published for each person's youth, not the higher "corrected" values that circulate online. Her correction is a group-level one and inflates the numbers by 5 to 25 points. Newton, for example, has 170 as his published value and shows up as 190 on many websites.

The numbers were taken from the book itself, which is in the public domain in the US, by cross-checking two scans and accepting only the values on which both agree.

Cox used the notion of mental age from that era, and her numbers don't compare point for point with a modern IQ. The list also reflects who the books of 1926 considered eminent: almost exclusively European men.

As a curiosity, the report shows a few figures whose Cox estimate falls within 10 points of yours, including below it. Never as "you have the IQ of," with no ranking and no badge. If your estimate is below 110, we don't show names, because the study has no figures in that range.

Einstein isn't in Cox's study. Contemporary people are left out too: the numbers that circulate for them have no source, and using a living person's image in advertising requires their permission.