President Trump says he’s a genius. Sometimes people even say it for him.

“You’re an (expletive) genius,” someone wrote to him on Twitter in 2013.

“I.Q. tests confirm!” Trump replied.

In fact, he wrote this weekend, his lifetime of success in business, TV and politics “would qualify as not smart, but genius … and a very stable genius at that!”

He’s been less enthusiastic about providing evidence of his intelligence.

Trump has repeatedly challenged people to IQ tests, but when someone once asked him to prove his own score, he simply replied: “The highest (expletive)!”

The Washington Post asked the White House if it would share his IQ test results on Sunday, if there are any, but got no immediate reply.

So be it. There’s no law that a president has to document his intelligence.

But if Trump doesn’t, he should know that someone might come along and try to measure it for him.

It’s happened before.

In 2006, a psychologist at the University of California at Davis applied a statistical algorithm to reams of presidential biographies, surveys, polls and other historical sources, and concluded that the smartest man to have ever occupied the White House was our sixth president, John Quincy Adams.

With an estimated IQ between 165 and 175, Adams was a genius by any common definition of the term, according to the study. By comparison, most people score about 100. (A child with an IQ in the 160s was declared smarter than Albert Einstein and Stephen Hawking by international tabloids.)

There are, of course, many asterisks beside Adams’ big number. He never took an intelligence test, which Politico notes were not invented until the early 1900s, long after his death. And the definition and meaning of an IQ has evolved since then.

But as psychologist Dean Keith Simonton wrote in his 2006 study, Adams was among eight U.S. presidents declared geniuses in a 1926 study by an early intelligence researcher named Catharine Cox. She had sifted through the biographies of hundreds of famous people and worked out a method to estimate IQs based on childhood and adolescent achievements.

It’s not hard to see how Adams would have impressed her. As the University of Virginia’s Miller Center writes, he was the son of John Adams, the second U.S. president. Young Adams considered himself his family’s protector while his father was helping plan the Revolutionary War. He crossed the Atlantic at age 10, rode mules from Spain to Paris, and passed the bar exam in the new United States of America at 23.

Simonton took Cox’s IQ estimates for Adams and other early presidents, and cross-referenced them with biographical information for their modern-day successors. He used some clever statistical techniques to build an intelligence matrix for all the presidents up to George W. Bush – about whose intelligence he was most curious.

The psychologist claimed his method was nonpartisan and extremely accurate, and the journal Political Psychology deemed it robust enough to publish in 2006.

The second-smartest president in the study, by average score, was Thomas Jefferson – of the Declaration of Independence fame – followed by John F. Kennedy, who inspired his country to go to the moon.

Bill Clinton was the No. 4 White House genius, with an estimated IQ range between 136 to 159. Simonton explained why:

“His demonstrated capacity for mastering impressive amounts of complex and detailed information, his verbal eloquence and fluency, and his logical adroitness and sophistication – at times, as during the Monica Lewinsky scandal, verging on sophistry – places Clinton head and shoulders above his successor in terms of intellectual power.”

Keep in mind that the study was published before Barack Obama or Trump became president.

Incidentally, someone tried to cram Trump into the top of Simonton’s list during his presidential campaign, ranking him just below Adams in a meme that still proliferates.

That’s fake news, though. Snopes traced the meme to an article on a hoax site that claimed to have calculated Trump’s IQ as 156 based on his college acceptance standards. Among a host of “logical missteps and factual inaccuracies,” Snopes wrote, the article didn’t even name Trump’s freshman school correctly.

Trump does not appear to have ever revealed his score, if he really did a take test. Like Stephen Hawking, he even seemed dismissive of the concept of IQs in his autobiography, “The Art of the Deal”:

“You can take the smartest kid at Wharton, the one who gets straight As and has a 170 IQ,” Trump wrote with his co-author in 2009, “and if he doesn’t have the instincts, he’ll never be a successful entrepreneur.”

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