The initiative for the IQ tests came from the American quarter of the IMT partners. The lead psychological investigators of the defendants, Major Douglas Kelley and Lieutenant Gustave Gilbert, implemented a number of exams to the defendants over the course of 1945-46. The IQ tests were part of a whole battery of psychological tests ranging from Rorschach inkblots to psychiatric-informed interrogations.
Part of the reason for this type of testing was pragmatic. The Americans, much more so than their fellow prosecutors, saw the IMT as a didactic process for greater Germany that would educate the German population about Nazi crimes. The idea that Nazi leaders were psychopaths or otherwise insane needed to be dispelled for this purpose as it would eliminate one metaphorical barrier between the German public and the accused. Moreover, qualified psychological evaluations would also establish the psychological fitness for the defendants to stand trial and prevent an insanity defense. Rudolf Hess had already began what a number of his contemporaries thought was play-acting as insane while he was under detention in the UK. Gilbert and Kelley's examinations would eliminate this type of defense as well as ensuring the accused would be fit to stand trial under great publicity.
Yet the array of examinations also tapped into the American wartime preoccupation with the Nazi mind. There was a wartime cottage industry of books and articles that allegedly sought to explain what went wrong in Germany and was fueled by emigre psychologists, public intellectuals, and government studies. Some of these works tried to identify a specific German pathology present within the fabric of German society. Richard Brickner's provocatively-entitled 1943 book Is Germany Incurable? was one example of this oeuvre. Brickner suggested that German history made the population vulnerable to megalomaniac leaders and ingrained obedience. Other wartime pop psychology materials suggested Freudian roots of Nazism and that it attracted a certain personality type.
Nor were these psychological explanations of Nazism just limited to public consumption. Bruno Bettelheim's 1943 article "Individual and Mass Behavior in Extreme Situations," in the Journal of Abnormal and Social Psychology had a wide readership within American policy circles, including no less a figure than Eisenhower. Henry Dicks, a psychiatrist working for British intelligence, had already instituted a screening program among German POWs trying to set up a correlation between personality types and political leanings among captured German soldiers. Walter Langer produced a psychological study for OSS on Hitler's own personal psychology, much of it regurgitating gossip on Hitler's sexual proclivities.
The IMT thus seemed to be the perfect laboratory to evaluate this Nazi personality type. Gilbert and Kelley had unrestricted access to the prisoners, which was something the other gaolers did not have. The defendants for their part often played along with these tests, in no small measure because there was little else for them to do. They were under solitary confinement and there is much evidence that the dull routine of the prison was getting to them.
As to what exactly these tests revealed is quite debatable. The tests were normal for the standards of 1945, but that still limits their use as a diagnostic tool in 2017. Gilbert concluded that many of the defendants were functional psychopaths and some of his contemporaries echoed these claims. Later psychologists who examined the data are more skeptical. Mark Resnick and Vincent Nunno's 1991 reevaluation of the IMT data concluded that while there was a common authoritarian personality type among the defendants, these traits were more common for men who occupied positions of authority in hierarchical institutions like the military or government. Likewise, the collaborative book The Quest for the Nazi Personality by Zillmer et al concluded on IMT and POW data that there was a common personality type that gravitated to Nazism, these Nazi elite were not the crazed sadists of popular imagination.
Overall, the IQ tests represented what would become an enduring phenomena within Third Reich studies. The idea that something was fundamentally wrong on a psychological level with Nazis remains an attractive explanation for the events of 1933-45. The wartime fascination with diseased German minds has not abated and this subreddit is not immune to this line of questioning. But such psychological explanations are often quite elusive and the data produced by the IMT evaluations demonstrates the fragility of this explanation. They are most useful when speaking of generalities and tend to confirm logical suppositions. This makes the findings not as dramatic as they first might appear. For example, the IQ tests found most of the defendants scored quite high, but this should not be surprising since they were chiefs of their respective agencies and most had access to higher education. It is not an unreasonable assumption that had their Allied analogues been subjected to the same battery of IQ tests, their results would have been quite similar. While the IMT psychological testing will continue to be the subject of inquiry, they are more useful to historians as a sign of the zeitgeist of the era that was quite strong in the US that somehow the Nazi mind could be identified, explained, and measures put in place to eliminate it in the future.
Sources
Brunner, José. "“Oh Those Crazy Cards Again”: A History of the Debate on the Nazi Rorschachs, 1946–2001." Political Psychology 22, no. 2 (2001): 233-261.
Pick, Daniel. The Pursuit of the Nazi Mind: Hitler, Hess, and the Analysts. Oxford: Oxford University Press, 2014.
Robin, Ron Theodore. The Barbed-Wire College: Reeducating German POWs in the United States During World War II. Princeton, N.J.: Princeton University Pres, 1995.
Zillmer, Eric A. The Quest for the Nazi Personality: A Psychological Investigation of Nazi War Criminals. Routledge, 2015.