Commenter “Otto von Bismark” asked me to estimate Hitler’s IQ, and with Halloween only days away, it makes sense to examine one of history’s most terrifying boogeymen.

STATISTICAL PREDICTION

The most salient fact about Hitler was his historical influence.  Indeed when Time magazine named the most influential person of the 20th century, many felt that the title objectively belonged to Hitler, but because Hitler’s influence was so destructive and evil, the title was instead given to Albert Einstein for being the preeminent scientist in a century dominated by science.

But at the very least, Hitler was likely the most influential white gentile of the 20th century.  Roughly 8.7 billion people lived some time during the 20th century.  Assuming roughly 14% of them were white gentiles, then Hitler was the most influential out of 1.22 billion.  Thus, when it comes to influence, Hitler had a normalized Z score of +6.

The next most salient fact about Hitler was that he was a criminal.  Had he not committed suicide, he would have been hung for war crimes.  Criminals tend to come from less successful backgrounds than non-criminals, for example only a quarter of American men are as low income as the median criminal, suggesting criminals average a normalized Z score of -0.66 on measures of money and probably influence.  Thus, if relative to white gentilesn Hitler had a normalized Z score of +6 when it comes to historical influence,  the normalized Z score was likely +6.66 with respect to criminal white gentiles.

Thus, if there were a perfect correlation between IQ and influence, Hitler’s IQ would be 6.66 standard deviations above the average white criminal.  However the correlation between IQ and measures of worldly “success” appears to be about 0.4. This is the figure scholar Arthur Jensen (1998) gives for the correlation between IQ and income, and there’s probably a similar correlation between IQ and other measures of worldly success like power and influence, since elite politicians and top CEOs seem to be cognitively similar to billionaires.

Assuming a 0.4 correlation between IQ and influence, Hitler’s expected IQ would be 0.4(6.66) = 2.66 standard deviations above the average criminal.  Assuming white criminals average IQs around 90 with a standard deviation of 15, that would put Hitler’s expected IQ at 130.

Of course, the standard error around this estimate is quite large, so one needs independent verification from other methods.

HISTORIOMETRIC ANALYSIS

The most popular official IQ tests are the Wechsler intelligence scales which have traditionally been divided into a verbal scale (i.e. the ability to solve problems with words), and performance IQ (i.e. the ability to solve problems by manipulating objects), both of which were combined into a full-scale IQ, which was a measure of overall intelligence.  For Hitler, there is some evidence for his ability in both domains.

Hitler’s verbal IQ

Perhaps the best estimate of Hitler’s verbal IQ can be gleaned from his book Mein Kampf.  According to an internet commenter named “Thierry Etienne Joseph Rotty“, Hitler was an awful writer, though of course this is relative.  Rotty writes:

…Although he came up with the idea of writing Mein Kampf, most of the actual writing and typing was done by Rudolf Hess. When you look at the original pages you’ll see the version as dictated by Hitler, and then the re-writing Hess to make to make some sort of coherent sentences out of it. About half had to be re-written.

It should be noted that Rudolf Hess was one of 21 tried Nazi leaders who was administered a German version of the Wechsler-Bellevue.  Although his score on the verbal section seems unreported, his full-scale IQ was 120, and typically on the Wechsler scales, the verbal IQ correlates 0.92-0.95 with the full-scale IQ.  Thus if we assume that Hess had a verbal IQ of around 120, this puts a ceiling on Hitler’s likely verbal IQ, since Hess was the more competent writer, and writing skill is probably a good proxy for verbal IQ among amateurs.

Although Hitler’s verbal IQ was likely not above 120, we also have very good reason to assume it was not below 120.  On page 58 of the book  The Young Hitler I Knew: The Memoirs of Hitler’s Childhood Friend by  August Kubizek, it states:

From school sources there is abundant authentic material describing his school performance.  In primary school he was always near the top of the class.  He learned quickly and made good progress without much effort.

Anyone in an ordinary white school, who does better  than 90% of his classmates without much effort, must have a verbal IQ higher than 90% of whites (an IQ of 120 is often defined as the 90 percentile among whites in Western countries).

Since we have good reason to believe Hitler’s verbal IQ was neither above nor below 120, we can estimate it to be exactly 120.

Hitler’s Performance IQ

Probably the best estimate of Hitler’s performance IQ can be made from his drawings.  Although drawing ability is only moderately correlated with general intelligence, Flourcence L Goodenough felt the correlation was good enough to publish the Draw-a-Man IQ test in 1926.  Circa 1960 the test was revised and renormed by Dale Harris.  Using the 1963 manual, I found that this drawing, reportedly by a 19-year-old Hitler, obtained a score of 49 out of 73 points.

Of the 73 items on the Draw-a-man IQ test, I found the above drawing flunks items 10,12-15,27,38-43,50,52-53,55-62,and 69.  However items 55-59 all involved clothing.  These were irrelevant to Hitler’s drawing because his picture was for art school where they evaluate your ability to draw nudes.  Secondly, items 39-43 involved feet, and Hitler’s drawing does not extend to the feet.

Thus if it’s permissible to exclude the ten items that were not applicable to Hitler’s drawing, his prorated score becomes 57 out of 73.  According to circa 1960 unsmoothed norms published by Harris (1963, pg 102), U.S. boys and girls combined (age 15 which is roughly adult level for such tests) had a mean score of 45.5 out of 73 (SD = 10.19).  Thus Hitler’s prorated score of 57 would equate to an IQ of 117 (U.S. norms) or 116 (U.S. white norms for that era).

However Hitler made his drawing circa 1908 which is roughly 52 years before the above norms were obtained.  According to scholar Richard Lynn (2006), performance on this test has been rising by the equivalent of 3 points per decade which means norms from around 1960 would give results 16 points too low for a drawing made around 1908.  Since IQ by definition reflects your test performance compared to Western whites of your age and birth cohort, we must add 16 points, bringing Hitler’s performance IQ to 133.

Hitler’s full-scale IQ

Above I estimated Hitler’s verbal IQ to be 120 and his Performance IQ to be 133.  Had Hitler lived long enough to have been one of the 21 Nazi leaders tried at Nuremberg, he would have been administered a German version of the Wechsler-Bellevue intelligence scale.  I don’t know much about the German version, but on the American version, someone who is around the age Hitler would have been had he been tested, with a verbal IQ of 120 and a Performance IQ of 133 would have a full-scale IQ of 130.  This is exactly the same as the 130 I statistically predicted at the start of this post, based simply on Hitler being both a criminal and the most influential white gentile of his century.

It’s also similar to what blogger Anatoly Karlin had predicted based just on the average IQ of the Nazi leaders who actually were tested.

An IQ of 130 implies one is smarter than 98% of Western whites of one’s same age and birth cohort.

How would Hitler score compared to people today?

I must once again emphasize that IQs are calculated relative to a mean defined as 100 in the Western (white) population of the same age and time period.  If we could travel back in time to World War II and give Hitler the most current Wechsler adult IQ test (the WAIS-IV normed circa 2008), he likely would score 111 (using U.S. white norms) (19 points lower than the 130 he would obtain on a test given in his own time).  This phenomenon, known as the Flynn effect, is partly because people today have the advantage of more schooling than was typical of Hitler’s day, and schooling seems to artificially prop up scores on IQ tests without actually increasing real intelligence.  Thus when you give people from past generations a modern IQ test, they score lower by modern standards because the modern tests would be biased against them.

If we went back in time and gave Hitler only those WAIS-IV subtests that are not much impacted by schooling and obtained a prorated score based on this culture reduced part of the test, he would likely score 117.  Higher than the 111 he would score on a biased test, but still not as high as the 130 he would have likely scored on a test normed on his own generation.

The reason he would have scored lower on a modern test, even after the schooling biased tests are removed, is that in my opinion, as much as 66% of the Flynn effect reflects a genuine biological increase in real intelligence caused by better nutrition (including disease reduction) increasing the size and complexity of the brain over the 20th century, analogous to secular gains in height.

Alternative claims

Not everyone would necessarily agree with my conclusion that Hitler had an IQ of 130. Popular high IQ society writer Grady Towers felt Hitler’s IQ was likely among the very highest of the Nazi leaders (i.e. IQ 143) because otherwise those wolves would have torn him apart.  On the other hand, this source claims Hitler couldn’t be a mailman because he flunked an intelligence test because “his mental capacity suffered after he was gassed in the war”.  When it comes to a historical figure as controversial as Hitler, people say all sorts of things so it’s hard separating fact from fiction.

[Update: Nov 3/2015–For a followup discussion on Hitler’s IQ, check out Anatoly Karlin’s recent post on the topic.]