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Was William James Sidis the Smartest Man on Earth?

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The Logics

Was William James Sidis the Smartest Man on Earth?

William James Sidis 1914 - Public domain photograph originated from Wikimedia Commons and colored by Larry Gowdy

(PD) William James Sidis, 1914


Was William James Sidis the Smartest Man on Earth?

The World's Smartest Man?

Did William Sidis have an IQ of 250 to 300?

How did he score above the maximum for IQ tests?

Did his father believe that William was a genius?


Larry Neal Gowdy

Copyright©2008-2013 - Updated October 19, 2013



Related pages on The Logics website:

Boston Bombings Tied to William James Sidis

“Myths, Facts, Lies, and Humor About William James Sidis
— Part 1”

“Myths, Facts, Lies, and Humor About William James Sidis
— Part 2”

“Myths, Facts, Lies, and Humor About William James Sidis
— Part 3”

“Myths, Facts, Lies, and Humor About William James Sidis
— Part 4”

“Myths, Facts, Lies, and Humor About William James Sidis
— Part 5”

“Myths, Facts, and Lies About Prodigies
— A Historiography of William James Sidis.”

“William James Sidis - When a Prodigy is not a Prodigy”

“Type A and B Intelligence”

“Child Prodigy”

“IQ Questions and Answers”



Was William Sidis the smartest man on earth? The simple answer is I don't know and nobody ever can know. To date there still does not exist any substantiated evidence to support the claim that Sidis was the smartest man on earth, and without the evidence there can be no logical reason to entertain the idea. Nevertheless, there is evidence of how the myth was born and popularized.

In 1946, Abraham Sperling wrote “A Story of Genius,” an article that focused on the life of William Sidis.(1) In the article Sperling stated: “Helena Sidis told me that a few years before his death, her brother Bill took an intelligence test with a psychologist. His score was the very highest that had ever been obtained. In terms of I.Q., the psychologist related that the figure would be between 250 and 300. Late in life William Sidis took general intelligence tests for Civil Service positions in New York and Boston. His phenomenal ratings are matter of record.”(2) Sperling’s comments in the article appear to have predominately been based upon hearsay and popular beliefs of the time. Did the psychiatrist actually give an IQ test, or did the psychiatrist merely allude to Sidis’ civil service results as perhaps being the performance of an individual with an IQ of 250-300? Until the day that Sidis’ actual exam scores are made publicly available, it is not rational to form any belief about Sidis’ IQ that is based solely on Sperling’s comments.

Forty years later in 1986, Amy Wallace wrote the book The Prodigy: A Biography of William James Sidis, America's Greatest Child Prodigy.(3) On page 283 of The Prodigy it is stated: “Said Sperling… “In recent years, I have tested more than five thousand people. Of all the mentally superior individuals that I have seen, nobody begins to approach the intellect and perspicacity of William Sidis. According to my computations, he easily had an IQ between 250 and 300. …I have never heard of the existence of anybody with such an IQ. I would honestly say that he was the most prodigious intellect of our entire generation.””(4) Where or how did The Prodigy derive its version of Sperling's claim?

Sperling himself stated in 1946 that it was Helena that told him about the IQ score. According to The Prodigy, Sperling would have had to have given Sidis the IQ test before Sidis’ death in 1944. The two claims contradict, both appear to be based on hearsay, and neither claim can be accepted as evidence. If Sperling did give Sidis an IQ test, then why did Sperling not speak of it in A Story of Genius? If Sperling did not tell the truth about the test, then none of what he wrote can be trusted as factual, which also negates the 250-300 IQ claim for both Sperling and The Prodigy. If Sperling gave an accurate account of what he was told, then still his comments are invalid since they are based on hearsay.

Additional difficulties are found in how Helena Sidis was portrayed to have possibly had a tendency to exaggerate. William Sidis’ mother, Sarah Sidis, wrote in The Sidis Story: “He was not alone in this ability. Although his unleashed power enabled him to gain a workable knowledge of 25 languages, his father, Boris Sidis, was fluent in 50. After a little practice, either could master a new tongue within a week.”(5) On page 182 of The Prodigy it is claimed: “…and given William’s near perfect command of hundreds of languages and dialects.”(6) On page 126 of The Prodigy it is claimed: “William could learn a language in a day. According to Helena, “Billy knew all the languages in the world, while my father only knew twenty-seven. I wonder if there were any Billy didn’t know.””(7) Sarah Sidis is known to have had a tendency to exaggerate stories about the Sidis family, and so The Sidis Story cannot be trusted as being an accurate source of information. The Prodigy voiced the improbable claim that William Sidis could learn a language in one day, and when combined with the high quantity of other errors throughout the book, The Prodigy itself is found to have exaggerated its claims about William Sidis. The subtitle of the book itself, A Biography of William James Sidis, America's Greatest Child Prodigy, is a sensationalized claim of a thing that is not supported by evidence. The claim of Helena Sidis’, that William Sidis knew all the languages of the world, is of course an incorrect claim since it is quite impossible for anyone to live long enough to learn all world languages. If the alleged quote of Helena Sidis’ was correctly quoted, and it was not another invention by The Prodigy, then Helena Sidis was prone to exaggerate, and if Helena Sidis was Sperling’s sole source of information about William Sidis’ IQ, then there is reason to question the veracity of Helena Sidis' claim.

A hand-written letter of August 4, 1933 by William Sidis stated that he had taken a civil service exam, that he passed the state clerical exam, and that he was number 254 on the list; “not so encouraging” he wrote.(8) It is unknown if Sidis’ placement on a hiring list had any relevance to the IQ claim of 250-300, but if the letter is authentic, then the letter is evidence of Sidis having taken a civil service test as Sperling claimed in A Story of Genius. The question naturally rises, that if William Sidis took one or more civil service exams, and he was placed at 254 on one exam, and when combining the evidence of the letter with the possible evidence of Helena Sidis’ tendency to exaggerate, then it is necessary to speculate the possibility that Helena Sidis might have misunderstood what exams William Sidis took, or Helena Sidis may have purposefully twisted the job rank into being an IQ score. The simple fact is that no one can now know for sure what Helena Sidis was told or what she might have actually said. It is also possible, although probably not, that William Sidis did not tell the truth in the letter. Simply stated, there is no known verifiable evidence of William Sidis having had a 250-300 IQ. Until the day that William Sidis' IQ exam records are made public, the question will continue to ask what his rated IQ actually was.

A common opinion among some individuals within the high IQ community is that no currently used IQ test can accurately measure intelligence above about 140 to 150. A less common opinion is that no known IQ test can accurately measure intelligence at all, but rather IQ tests measure a small portion of the traits that are needed to create the thing termed intelligence. Also, different IQ tests do not use the same numbering system, and regardless of what Sidis' IQ might have actually been on whatever test(s) he may have taken, still there is the need to rank the test results by percentile. It is not reasonable to believe The Prodigy's claim that Sperling could accurately judge Sidis to be above a 99.99999999 percentile rank if Sperling had only tested about 5,000 individuals. What was the average IQ of civil service workers in the early 20th century? Some city civil service jobs today still only require a 6th to 9th grade education, and it is possible that city psychiatrists in cities as large as Boston and New York may not have had the opportunity to give IQ tests to many college educated individuals. Until the day that every individual on earth has been thoroughly judged of their intelligence, it cannot be determined if Sidis or anyone else was the smartest person on earth. To best determine the veracity of the claim that Sidis had a 250-300 IQ, first there needs to be authenticated evidence of what type of IQ test Sidis took, plus the actual answers Sidis gave, along with an evaluation of how well the psychiatrist was able to grade IQ tests. Sidis may have had a relative 250-300 IQ, no one knows, but there is no logical reason to believe that it might be true, while there is substantial evidence that the 250-300 claim is untrue.





I have been researching the veracity of primary sources of various subjects for about twenty-eight years, and never before have I found a topic so satiated with lies, myths, half-truths, exaggerations, and other forms of misinformation as is in the history behind William Sidis. Since 1904, the story of William Sidis has predominately been guided not by evidence and scholarly research, but rather by the emotions of whether biographers liked or disliked Sidis.

If a person desires to believe that William Sidis or anyone else is/was the smartest man on earth, then first define the term “smart.” Until the term is perfectly defined and unanimously accepted as valid by all people, then never can there be a smartest man on earth since there does not exist a definitive public clarification of what “smart” means.

The above information was adapted from a small portion of my research notes that include the topic of William Sidis. Myths, Facts, and Lies About Prodigies – A Historiography of William James Sidis gives additional depth into numerous myths surrounding the Sidis story.(9)


Addendum January 18, 2009:


Boris Sidis was said to have scoffed at intelligence tests. Is it not curious that Boris Sidis repeatedly boasted of his success in creating the prodigy William Sidis, and yet Boris Sidis chose to not speak of an intelligence score for William Sidis?

In 1903 Binet published L'Etude experimentale de l'intelligence that described Binet’s methods of intelligence testing. William Sidis would have been about eight years old when Lewis Terman revised Binet’s intelligence test in 1906. In 1914 Boris Sidis wrote within The Foundations of Normal and Abnormal Psychology: “The same holds true of the practical pseudo-psychology that has invaded the school, the court, the prison and the immigration bureau. The intelligence tests are silly, pedantic, absurd, and grossly misleading.” In 1919 Boris Sidis repeatedly spoke of genius in Philistine and Genius while apparently alluding to William Sidis, but again Boris Sidis gave no reference to IQ scores that William Sidis might have possessed.

It is very difficult to imagine that Boris Sidis might not have known about Binet’s work, and just as difficult to imagine that Boris Sidis would not have tested William Sidis. Considering William Sidis’ early talents with languages and mathematics, surely he would have scored well on an intelligence test, or would he?

Why would Boris Sidis, one of America’s leading psychologists of his era, not flaunt a 250-300 IQ for William Sidis? Surely Boris Sidis’ words in The Foundations of Normal and Abnormal Psychology give the reader a clue that though William Sidis may have been quite brilliant academically, William Sidis’ actual IQ scores may not have been as high as Boris Sidis might have preferred, nor as high as many people today desire to believe. But I side with Boris Sidis, that intelligence tests mean little, and less important are the scores, for no mathematical score can weigh the value of a man, and neither should the importance of William Sidis' life be measured by an IQ score.


Addendum June 22, 2010:


An interesting quote from The Prodigy that continues to beg for answers: "When Helena was six and Billy sixteen, he asked her for advice about something. She replied, "But, Billy, I'm a child. Why do you ask me?" He answered, "You have good common sense."(10) As the stories are told, Helena Sidis did not receive a similar education as William Sidis', and Boris Sidis may have been less than supportive of her education due to her being a female, but if the quote was authentic, and William Sidis did think of his sister as having good common sense at six years old, then there is a possibility that Helena was no less talented than any other member of the family, and in some ways she might have been the more sensible one. Hypothetically, and based on what is common within many families, daughters often have superior academic talents than sons, and so the possibility exists that if Helena had received a similar education as William's, then she might have exceeded his academic achievements. Nevertheless, though Helena appears to have held ample intelligence herself, it is believed that the circumstances surrounding William's prenatal development were a large influence on William's talents, and since a similar prenatal environment may not have existed for Helena, then there was less of a chance of her doing as well academically even if she would have had a similar formal education. Several times I have heard comments that some people believed Helena to have not been intelligent, and though the possibility exists that she may have been prone to exaggeration, from the little information available to me I suspect that she may have possibly been quite bright herself.


Addendum March 26, 2013:


Recent discoveries from the SesquIQ SQ tests have now verified a portion of the differences of human cognition (please see the Beyond Prodigies website for more information.) Based upon the available historical evidence, William Sidis is classified as a normal human, and while Sidis may have been an academic prodigy, there is no evidence whatsoever that Sidis' talents exceeded what is normal for humans, nor can the evidence suggest that Sidis might have been the world's smartest man.

Also important to be clarified is that the numerous articles and books about William Sidis were written by individuals who expressed their opinions, and regardless of whether the opinions were accurate or inaccurate, the final decision of whether to believe or disbelieve history boils down to what the public wants to believe. The public only buys books that the public wants to read, and the successful author knows how to spin a story to fit what the public wants to hear. Books like The Prodigy and The God Delusion may be a few steps — or giant leaps — away from possessing flawless knowledge, but the books are popular, which means that the authors wrote what the public wants to read, and if the books' information is slanted to fit popular demand, then the blame rests solely on the public and not on the authors. I just wanted to clarify in print that I personally interpret Amy Wallace's writing style to be of above-average quality, and though I may not agree with the words within The Prodigy, my disagreements do not in any manner lessen my respect for the author herself.






(1) Abraham Sperling, "A Story of Genius", Psychology for the Millions, 1945, pages 332-339.
(2) Sperling, "A Story of Genius".
(3) Amy Wallace, The Prodigy: A Biography of William James Sidis, America's Greatest Child Prodigy, 1986, page 283.
(4) Wallace, The Prodigy, page 283.
(5) Sarah Sidis, The Sidis Story, about 1950, unpublished.
(6) Wallace, The Prodigy, page 182.
(7) Wallace, The Prodigy, page 126.
(8) William Sidis, http://www.sidis.net, 08-03-1933.
(9) Larry Neal Gowdy, Myths, Facts, and Lies About Prodigies – A Historiography of William James Sidis, 2008.
(10) Wallace, The Prodigy, page 98.






Myths, Facts, and Lies About Prodigies, A Historiography of WIlliam James Sidis

Myths, Facts, and Lies About Prodigies
A Historiography of WIlliam James Sidis

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