Short answer: Abraham Lincoln never took an IQ test. Catharine Cox's 1926 Stanford study rated him 125 in childhood and 140 as a young adult, or 145 and 150 after correcting for thin records. Dean Keith Simonton's 2006 study of the presidents adopted those four figures, which average 140. All are estimates drawn from biography, not scores.
At a glance
| Estimated IQ | 125–150 (Cox); mean of the four figures 140 |
|---|---|
| Basis of estimate | Cox (1926), reused in Simonton (2006), Political Psychology 27(4) |
| Measured score | None on record |
| Born – died | February 12, 1809 (Kentucky) – April 15, 1865 (Washington, D.C.) |
| Field | Law, politics |
| Signature achievement | Emancipation Proclamation (1863); Gettysburg Address (1863) |
| Comparable minds | George Washington, Thomas Jefferson |
The four numbers
Lincoln is one of the 301 subjects in Catharine Cox's The Early Mental Traits of Three Hundred Geniuses (1926). His case sits in her chapter for subjects rated 120 to 130 on childhood evidence, well below the 140s where Jefferson and Franklin appear.
| Period | As rated | Corrected for reliability |
|---|---|---|
| Birth to 17 | 125 | 145 |
| Ages 17 to 26 | 140 | 150 |
In 2006 the psychologist Dean Keith Simonton estimated IQs for all 42 presidents in Political Psychology. For the presidents Cox had already rated, Lincoln among them, he used her figures unchanged. The four average exactly 140. His biography is at Abraham Lincoln, and the logic of retrospective scoring is laid out in historical IQ estimates, explained.
A frontier education, by his own count
The low childhood figure reflects the thin record of a frontier boyhood. Lincoln described it himself. In an 1859 sketch he wrote that no qualification was ever required of a teacher beyond "readin, writin, and cipherin" to the Rule of Three. In his 1860 campaign autobiography, written in the third person, he added: "Abraham now thinks that the aggregate of all his schooling did not amount to one year."
He learned law by reading it. "He studied with nobody," the 1860 sketch says. He was licensed to practice in Illinois on September 9, 1836, served four terms in the Illinois House from 1834 to 1842, and sat in the U.S. House from 1847 to 1849. Cox's corrections exist for records like this one: they push estimates up where early evidence is sparse, which is why his childhood figure moves from 125 to 145.
Euclid after Congress, a patent at 40
Lincoln kept training his mind as an adult. The 1860 autobiography records that "he studied and nearly mastered the six books of Euclid since he was a member of Congress." He was about 40 when he took up geometric proof for its own sake.
On May 22, 1849, he received U.S. Patent No. 6,469 for a device for "Buoying Vessels Over Shoals": inflatable chambers meant to lift a riverboat off a sandbar. He remains the only president to hold a patent. He later praised the patent system for adding "the fuel of interest to the fire of genius."
The evidence in the prose
Lincoln's strongest cognitive record is verbal. He debated the expansion of slavery with Stephen Douglas seven times in 1858, and his Cooper Union address in New York on February 27, 1860, raised him to national prominence. The preliminary Emancipation Proclamation followed on September 22, 1862, and the final one on January 1, 1863.
At Gettysburg on November 19, 1863, he spoke about 270 words. Five manuscript copies survive, each named for the person who received it. Compression of that order, argument reduced to its load-bearing sentences, is the skill that verbal-reasoning subtests on modern IQ tests try to sample, crudely and in minutes.
Lincoln beside Washington, Jefferson and Churchill
| President | Childhood, as rated | Ages 17–26, corrected | Mean of four |
|---|---|---|---|
| Abraham Lincoln | 125 | 150 | 140.0 |
| George Washington | 125 | 140 | 132.5 |
| Thomas Jefferson | 145 | 160 | 153.8 |
| John Quincy Adams | 165 | 175 | 168.8 |
Lincoln and Washington start level at 125; Lincoln pulls ahead in young adulthood. Winston Churchill, the leader he is most often paired with, has no Cox estimate at all, because Cox covered only people born between 1450 and 1850. See Winston Churchill's IQ and the side-by-side records in Lincoln vs. Churchill and Lincoln vs. Washington. For the scale, see IQ 140 and IQ 150.
Why the childhood figure misleads
Cox's method rewards documented precocity. A child whose tutors, letters and early verses survive earns a high rating; a child on the Indiana frontier leaves almost nothing to score. Critics, the paleontologist Stephen Jay Gould among them, argued that her estimates track the volume of surviving information as much as ability. Lincoln is the clearest case in the presidential sample: the less that was written down about his early years, the lower his first number.
Simonton's study makes a broader point that survives the caveat. Across 42 presidents, estimated intelligence correlated with historians' ratings of leadership. Lincoln's case shows the reverse is also informative: an unremarkable childhood score is no ceiling on adult performance.
How we assessed this
Lincoln's four figures come from Table 1 of Simonton's 2006 paper and match his placement in Cox's table of contents; the History News Network's 2006 review of the study independently reports the 150. Quotations come from the texts of Lincoln's 1859 and 1860 autobiographical sketches. Patent details come from Smithsonian magazine.
Frequently asked questions
What was Abraham Lincoln's IQ?
No test score exists. Catharine Cox's 1926 study estimated 125 for his childhood and 140 for ages 17 to 26, or 145 and 150 after correcting for gaps in the record. Dean Keith Simonton's 2006 presidential study used the same figures, which average 140.
Was Abraham Lincoln a genius?
Many historians would say yes, on the strength of his prose, his legal reasoning and his self-education. With less than a year of formal schooling he taught himself law, worked through Euclid in his forties, earned a patent and wrote the Gettysburg Address. His estimated IQ of 140 to 150 is high; his achievements outrun it.
Who had a higher IQ, Abraham Lincoln or George Washington?
On Cox's figures, Lincoln. Both are rated 125 in childhood, but Lincoln's corrected young-adult estimate is 150 against Washington's 140, and his four-figure average is 140 against 132.5. See George Washington's IQ for the full comparison.
How much formal schooling did Lincoln have?
Less than a year in total, by his own account. His 1860 autobiographical sketch says the aggregate of all his schooling did not amount to one year. Frontier teachers were expected to teach little beyond reading, writing and arithmetic to the Rule of Three. He learned law, grammar and geometry on his own.
Why do some websites list Lincoln's IQ as 128?
That figure takes Cox's corrected estimate of 150 and subtracts about 22 points for the Flynn effect, the rise in test scores during the 20th century. Cox made no such adjustment, and there is no reliable way to apply a population trend to one person born in 1809.
Sources
- Simonton, D. K. (2006). Presidential IQ, Openness, Intellectual Brilliance, and Leadership. Political Psychology 27(4), 511–526 — Table 1: Lincoln 125, 145, 140, 150; method and findings
- Cox, C. M. (1926). The Early Mental Traits of Three Hundred Geniuses (Internet Archive) — Lincoln's case in the chapter for AI IQ 120 to 130; subjects limited to 1450–1850
- Presidential IQ, by Thomas C. Reeves (History News Network, 2006) — Secondary report of Simonton's figure for Lincoln (150)
- Abraham Lincoln's Autobiographies of 1858–60 (Abraham Lincoln Online) — Schooling, Euclid and legal self-education quotations
- Abraham Lincoln Is the Only President Ever to Have a Patent (Smithsonian) — Patent No. 6,469, May 22, 1849; 'fuel of interest' remark
- Abraham Lincoln (Wikipedia) — Dates of bar license, legislative service, debates, Cooper Union, Emancipation Proclamation
- Gettysburg Address (Wikipedia) — Five known manuscript copies and their length
- Cox's IQ Estimates of 301 Eminent Geniuses (IQ Comparison Site) — Lincoln 150 corrected; 128 after a Flynn-effect subtraction
Editorial standard: IQ figures for historical figures are retrospective estimates and are labeled as such; scores for living people appear only when the person disclosed them or a reputable outlet reported them. Corrections: contact the editors.
