The smartest US presidents

These presidents also have LifeScore profiles. Their Simonton figures are not shown because we could not check them against two sources, so they are listed by the profile estimate instead.

Simonton did not test anyone. He took ratings of each president's "intellectual brilliance" and openness to experience from earlier expert surveys, linked them statistically to the Cox 1926 estimates for the eight presidents Cox had covered, and produced several versions of an IQ estimate for all 42 presidents up to George W. Bush. He called the results tentative. The ranking below uses his version II-C, the one the press usually quotes, and shows LifeScore's own profile estimate alongside it.

The two columns differ for a reason. LifeScore profiles for presidents Cox studied, such as Jefferson, John Quincy Adams and Lincoln, start from Cox's figure and adjust it for her high old scale. Simonton's figures sit on his own scale. Neither is a measured score, so the gap between them is a good picture of how uncertain any presidential IQ really is.

The top of the list is dominated by scholar-presidents. John Quincy Adams translated classical texts, taught rhetoric at Harvard and spoke several languages; Jefferson and Madison were among the best-read men of the founding era; Woodrow Wilson is the only president with an earned PhD; Jimmy Carter trained in nuclear engineering. Simonton's method rewards exactly that kind of record, because it rests on how intellectually brilliant historians judged each man to be.

Below about 145 the numbers bunch tightly. Coolidge, Hoover and Reagan all sit at 142 in version II-C, and Johnson, Truman and Monroe follow within three points. Simonton himself warned that neighbouring presidents cannot really be told apart, so read the middle of this list as a group rather than as a ladder.

Greatness and IQ are not the same ranking. Lincoln and Franklin Roosevelt top most historians' lists of the greatest presidents without topping this one, and Simonton found that intellectual brilliance predicts rated greatness only moderately. Political skill, judgement under pressure and the crisis a president faced matter at least as much.

In 2001 an email claimed that a "Lovenstein Institute" in Scranton had measured the IQ of every modern president, putting Bill Clinton at 182 and George W. Bush at 91. The institute never existed, the numbers were invented, and the story was debunked within weeks. It still circulates. If you see a list with Clinton far above every other president, it comes from that hoax, not from research.

Simonton's study is different in kind: it is published in a peer-reviewed journal, explains its method and data, and gives each president several estimates so readers can see the spread. That is why this page uses it and nothing else for the presidential column.