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Can you be a success even if you weren't the smartest kid? One answer might come from the estimated IQs of the men who served as president of the United States.

A researcher from the University of California at Davis came up with IQ scores using biographical information about the presidents' openness, "intellectual brilliance" and leadership.

See who's highest and who's lowest. An average IQ is around 100. Did higher IQs yield greater achievements? We include information about each prez's smart or not-so-smart decisions.

Presidents Barack Obama and Donald Trump aren't part of the ranking — they came along after the IQ research was conducted.

1. (Highest) John Quincy Adams

President John Quincy Adams
Wikimedia Commons / Public Domain

IQ score: 168.75

While studying law at Harvard University, America's future sixth president (1825-1829) became romantically involved with a local woman, but his parents advised him to establish his career before marrying her.

Brokenhearted or not, Adams listened to the advice — and went on to become one of the most respected and productive presidents ever.

He's remembered for his diplomatic skills: he settled the Treaty of Ghent and ended the War of 1812; negotiated with Britain over the location of the U.S. border with Canada; and purchased Florida from Spain.

His successes sure make a good case for choosing duty over love…

2. Thomas Jefferson

President Thomas Jefferson. Official presidential portrait by Rembrandt Peale
Wikimedia Commons / Public Domain

IQ score: 153.75

Officially, Thomas Jefferson was a planter, lawyer and politician — but he also had in-depth knowledge of mechanics, several languages and architecture, and he was a talented surveyor and mathematician.

He was an extremely busy man with a huge range of interests that he kept under control with a very strict schedule: He rose with the sun, ate breakfast strictly at 8, had a big lunch at 3, and kept track of everything in a trusty notebook.

Jefferson's achievements include writing the Declaration of Independence when he was in his early 30s.

As the third president (1801-1809), he: doubled the country’s territory; negotiated peace with France; and developed American trade. He remained an overachiever after retiring from office, when he founded the University of Virginia.

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