Thomas Edison's IQ: The 'Addled' Schoolboy and the Record That Followed

Why no number exists

Edison was 58 when the Binet–Simon scale, the first practical intelligence test, appeared in 1905. No record shows he ever sat one. The retrospective route does not help either. Catharine Cox's 1926 Stanford study built IQ estimates for 301 eminent people who lived between 1450 and 1850, drawn from James McKeen Cattell's list of the thousand most eminent figures in history. Edison, born in 1847 and still working when her book appeared, is not among them.

So the question has to be answered from the record. His full profile is at Thomas Edison, and the reasons historical figures cannot simply be assigned scores are set out in historical IQ estimates, explained.

The 'addled' story: what the record says

The anecdote is real, and its source is specific. Edison: His Life and Inventions, the 1910 biography by Frank Lewis Dyer and Thomas Commerford Martin, says the Port Huron public school gave Edison "all the regular scholastic instruction he ever enjoyed—just three months." By his own recollection he was always at the foot of the class and had come almost to regard himself as a dunce.

The book then describes his mother as "hotly indignant upon hearing that the teacher had spoken of him to an inspector as 'addled.'" Nancy Edison, a former teacher, took him out and taught him at home. The Thomas A. Edison Papers project at Rutgers gives a slightly fuller account: two brief periods of school in Port Huron, with most of his education at home.

The version that circulates online, a letter from the school that his mother read aloud as praise, does not appear in the 1910 account. There, the remark was spoken to an inspector, and no letter is mentioned.

A mother's syllabus

What Nancy Edison assigned was demanding. According to Dyer and Martin, before he turned 12 he had read, with her help, Gibbon's Decline and Fall of the Roman Empire, Hume's History of England, Sears' History of the World and Burton's Anatomy of Melancholy, and he tried to struggle through Newton's Principia.

Edison credited her directly: "My mother taught me how to read good books quickly and correctly." As a young telegrapher he moved on to trade periodicals and Michael Faraday's Experimental Researches in Electricity. The pattern, heavy self-directed reading followed by hands-on trial, would define the rest of his career.

The output: 1,093 patents

Edison's first patent, U.S. No. 90,646 for an electric vote recorder, was granted on June 1, 1869. He built his laboratory at Menlo Park, New Jersey, in 1876. In early December 1877 his team demonstrated the phonograph at the offices of Scientific American in New York.

The lamp came next. His team's first successful carbon-filament test, on October 22, 1879, burned for 13.5 hours. He filed for a patent on November 4, 1879; it was granted on January 27, 1880. Carbonized Japanese bamboo later pushed filament life past 1,200 hours. Edison did not invent the incandescent lamp. Joseph Swan in England demonstrated a working lamp in early 1879, and others came before both men. Edison's achievement was a practical lamp and the system to power it: the Pearl Street Station in Manhattan began service on September 4, 1882.

A larger laboratory at West Orange followed in 1887, and the Kinetoscope, an early motion-picture viewer, in 1891. By the end of his life his name was on 1,093 U.S. patents. Congress awarded him a gold medal on May 29, 1928.

The mind as a system

Edison's distinctive talent was organizational as much as individual. Menlo Park functioned as an invention factory, staffed by expert machinists and experimenters who attacked problems from filament materials to dynamo design. The Edison Papers note he also worked on marketing and on questionnaires for hiring.

He described his method in a line printed in the Idaho Daily Statesman in 1901, the earliest known version according to Quote Investigator: "Genius," says Edison, "is 1 per cent inspiration and 99 per cent perspiration." It was a claim about process, not intelligence. An IQ test samples reasoning in a single sitting; Edison's record reflects persistence over decades.

Edison and Tesla: what can be compared

Edison is most often set against Nikola Tesla. Neither man has a measured score, and neither appears in Cox's study; Tesla was born in 1856, after her cutoff. Popular rankings that put Tesla far above Edison are comparing guesses. See Nikola Tesla's IQ, and for the substance of their rivalry, Tesla vs. Edison and the head-to-head profile.

The American inventor with an actual scholarly estimate is Benjamin Franklin, rated 160 after correction in Cox's study. See Benjamin Franklin's IQ and Franklin vs. Edison. Whether Edison would have cleared the Mensa line at IQ 130 or scored far above it cannot be known.

How we assessed this

We checked Cox's selection criteria and table of contents and confirmed Edison is not among her subjects. The schooling story is taken from the 1910 Dyer and Martin biography and the Rutgers Edison Papers; patent and laboratory dates come from the Edison Papers and Wikipedia; the lamp chronology comes from Wikipedia's history of the incandescent bulb.

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.