Zach Hambrick is a professor in the Department of Psychology at Michigan State University. His research focuses on individual differences in cognitive ability and complex skill. He is a fellow of the Association for Psychological Science.

What are we to make of President Donald Trump’s boasts that he has a higher IQ than a member of his Cabinet, Secretary of State Rex Tillerson? Amid reports that Tillerson called Trump a “moron”—a claim Tillerson passed up a chance to deny on Sunday—Trump told Forbes magazine, “I guess we’ll have to compare IQ tests. And I can tell you who is going to win.” White House press secretary Sarah Huckabee Sanders later clarified that Trump “never implied that the secretary of state was not incredibly intelligent”—suggesting that Trump believes his IQ is astronomically high, maybe even the very best. In the past, he has described his IQ as “very high,” “much higher than [that of Presidents Bush and Obama],” “much higher than [the intellectuals’],” and “the highest, asshole!” Before Tillerson, Trump challenged the mayor of London and anyone who said he doesn’t understand global warming to IQ smackdowns.

But what would an IQ face-off between Trump and Tillerson—or anyone else—even tell us? Should we care whether our president has a high IQ?


Short for intelligence quotient, an IQ score represents a person’s overall level of performance on a battery of cognitive ability tests. IQ evaluations typically include both verbal tests, such as vocabulary and reading comprehension, and nonverbal tests, such as mental rotation and abstract reasoning. They may also include tests of general knowledge with questions such as What is the capital of Belgium?, and tests of working memory that require the test-taker to remember and mentally manipulate information. In a working memory test called “backwards digit span,” the test-taker is read a series of digits such as 4 5 8 1 6 9 7 and must repeat them in the reverse order.

The first standardized test of intelligence was introduced in the early 1900s by French psychologist Alfred Binet and his colleague Théodore Simon. Commissioned by the French government to develop an instrument for identifying slow learners in Paris schools, the Binet-Simon test included 30 progressively more difficult problems to measure “good judgment,” which Binet saw as the defining characteristic of intelligence. In one of the easiest problems, the child was presented with half a chocolate bar and a block of wood to see whether he would make a distinction between the objects before trying to eat one of them. In one of the most difficult problems, the child was asked to describe the distinction between pairs of words such as weariness and sadness. In subsequent versions of the Binet-Simon test, the items were grouped by age level, and a child’s score on the test was expressed in terms of their mental age. If a 6-year-old child answered the same number of questions correctly as the average 8-year-old, she was assigned a mental age of 8. But if she answered the same number of questions correctly as the average 4-year-old, she was assigned a mental age of 4. Mental age was then used to determine whether the child needed special attention.

In 1916, an English version of the Binet-Simon test was published by the Stanford University professor Lewis Terman as the first edition of what would become known as the Stanford-Binet Intelligence Scales. Terman added problems to make the test more suitable for adults. He also incorporated the German psychologist William Stern’s IQ formula, which stipulated that a person’s IQ is their mental age divided by their chronological age, multiplied by 100. For example, if a 4-year-old child scored at the level of the average 6-year-old child, his IQ would be 150. This formula made it easy to interpret and compare IQ scores, but as the columnist Walter Lippmann observed writing in the New Republic, this way of scoring the test led to the nonsensical conclusion that “the average mental age of Americans is only about fourteen.” This is because scores on certain types of cognitive ability tests, such as those requiring quick responses, decline as we get older. To take care of this problem, Stern’s formula was eventually replaced by a formula in which IQ reflects a person’s deviation from the average score for people of a similar age.

Now in its 5th edition, the Stanford-Binet includes two basic types of subtests—verbal and nonverbal. The verbal tests measure vocabulary and reading skills, whereas the nonverbal tests measure a person’s ability to think logically and solve novel problems. Other IQ tests, such as the Wechsler Adult Intelligence Scale and the Woodcock-Johnson Psychoeducational Battery, are set up similarly. These tests are used for a wide range of purposes in society, including to diagnose learning disabilities and neurological impairment. In states with capital punishment, scores on IQ tests may even be considered in determining whether a person is eligible for execution, as the Supreme Court ruled in 2002 that it is cruel and unusual punishment to execute a person with an intellectual disability.

But does an IQ score capture anything important, beyond a person’s skill in taking an intelligence test? Does it measure anything that matters to people in their lives? Few questions have generated more controversy in the history of psychology. One thing that is clear is that a high IQ doesn’t guarantee success in school, work or any other area of life. You can probably think of a person who did extremely well on the SAT—which the multiple intelligence theorist Howard Gardner once described as a “thinly disguised intelligence test”—but who floundered in college. Moreover, IQ tests miss characteristics of people that are important for success in the world. For example, they don’t measure a person’s social skills or how careful they are in their work. Nor do they measure a person’s emotional stability and their ability to handle stress.

All the same, scores on IQ tests do predict a wide range of real-world outcomes to a statistically and practically significant degree, including academic achievement, job performance, and even health and longevity.

As it happens, there is evidence that IQ predicts success in the job of U.S. president. In a 2006 study published in Political Psychology, the psychologist Dean Keith Simonton estimated the IQs of the first 42 presidents (George Washington to George W. Bush). Of course, Simonton couldn’t administer an IQ test to his subjects. Instead, using a statistical approach, he derived IQ estimates from published information reflecting presidents’ educational and professional achievements, as well as their standing on personality traits known to be related to IQ, such as intellectual openness. Simonton’s analysis revealed that there was a wide range of scores—from around 110 (Warren Harding) to 165 (John Quincy Adams). Furthermore, the IQ scores correlated positively with an independent index of “presidential greatness,” based on historians’ ratings of U.S. presidents on leadership performance.

Perhaps not surprisingly, this finding indicates that we should want the smartest person we can have in the Oval Office. All else equal, a president with a high IQ should be better able to synthesize large amounts of information and make good decisions than a president with a lower IQ. At the same time, Simonton’s findings suggest that much more goes into being an effective president than having a high IQ. An even stronger predictor of presidential greatness than IQ was what Simonton called “intellectual brilliance.” A person high in this personality trait is not just smart—they are insightful, original and wise. Abraham Lincoln’s decision to issue the Emancipation Proclamation comes to mind, as does John F. Kennedy’s use of creative diplomacy to end the Cuban missile crisis.

Trump’s IQ is probably not nearly as high as he says it is (an official report of his IQ has not materialized). Notwithstanding his claim that he has the “best words,” his command of language is not impressive. He once tweeted that China’s theft of a U.S. Navy drone in international waters was an “unpresidented act.” And asked how much a Mexican border wall would cost, he produced this utterance: “I think $10 billion or less. And if I do a super-duper, higher, better, better security, everything else, maybe it goes a little bit more.” There are also significant gaps in Trump’s knowledge of history and the world, as evidenced by now-famous observations such as “Frederick Douglass is an example of somebody who’s done an amazing job and is getting recognized more and more, I notice” and “Belgium is a beautiful city.” This suggests that Trump doesn’t read much, or else doesn’t absorb what he reads. It could also be that his well-documented proclivity to contradict himself reflects an inability to reason through the logical implications of his various claims.

But it would be a serious mistake to focus too much on Trump’s IQ, whatever it is. And it’s a mistake for him to focus too much on it as well. As the findings of Simonton’s study suggest, if the president really wants to have something to brag about, he should work on displaying imagination, originality and wisdom.