What does science say? For obvious reasons, it is not possible to have the 43 U.S. Presidents sit for an IQ test. Thus, in a 2006 study, the University of California Davis psychologist Dean Keith Simonton used a historiometric research approach to estimate the correlation between IQ and presidential success. In the conventional approach to measuring IQ, a person is given a standardized test, such as the Wechsler Adult Intelligence Scale, and their score on the test is assumed to reflect their level of intelligence (with some amount of random error). By contrast, in the historiometric approach, a person’s IQ is quantitatively estimated based on variables having known correlations with IQ, such as highest level of education, academic honors, scores on college admissions exams, occupation, and preferences. In his study, Simonton found that IQ estimates for the first 42 presidents (Washington to G. W. Bush) ranged from 118—around the average for a college graduate—to a stratospheric 165—well beyond the conventional cutoff for “genius.” (The three lowest, from the bottom, were Ulysses S. Grant, Warren Harding, and James Monroe. The three highest, from the top, were John Quincy Adams, Thomas Jefferson, and John F. Kennedy.) What’s more, IQ correlated positively with a measure of “presidential greatness” based on multiple rankings and ratings of presidents’ leadership ability—and the relationship went in a straight line. The smarter the president, the better, roughly speaking. Simonton’s IQ estimates also correlate positively with a ranking of presidential performance compiled by statistician and FiveThirtyEight.com founder Nate Silver.