Defense Mechanism Test (DMT)

A sensitive test for assessing the ability to judge info correctly under stress

Used for selection of combat pilots as well as top executives

Jaan Suurküla, M.D.


This test has been used worldwide as a combat pilot selection instrument since about 40 years and has drastically reduced the frequency of pilot errors due to severe stress, the most common cause for flight accidents. It detects defense mechanisms, that prevent the pilot from assessing the situation realistically in acute stressful conditions. These defenses bring about a distortion of the perception, like ignoring a warning signal, or interpreting it to be irrelevant or changed (eg a blinking signal perceived as steady).

This behavior occurs in people with trait anxiety, a disturbance mostly developed in childhood. To alleviate anxiety, subconsciously these people acquire the habit of using defense mechanisms that change the perception of the situation so as to appear less threating. This disturbance is very common in modern society.

The test is also being used for selection of civil pilots by some airlines, including SAS. It has also been used successfully for selection of top executives and other professionals who must be able to assess information realistically under stressful conditions.


A great problem in combat pilot training all over the world has been that common psychological tests have not been able to reveal the deeply seated disturbances that make persons unable to keep the mind cool in highly stressful situations. In Sweden, a major part, sometimes even 80% of the pilot trainees, dropped out during flight training, year after year. With few exceptions, the reason was an inability to act  adequately under demanding flight situations. The situation has been similar in other air forces, which meant great economic losses considering the high (mainly fuel) costs of pilot training.

Therefore the Swedish Air force sponsored the development of a test designed to reveal hidden psychological disturbances. The “Defense Mechanism Test” (DMT), originally created by professor Ulf Kragh, was modified in important respects by the psychologist Thomas Neuman and was introduced in the Air Force 1970. As there are fundamental differences between Kragh’s method and the way Neuman applies it, we will call it “DMT-Neuman”.


This test detects disturbances in the perception of threatening pictures presented in a fraction of a second. It is experienced as a very brief flash that one only gets a very vague idea about. This is called subliminal perception. Persons with pronounced defense mechanisms react spontaneously with anxiety (indicated a/o by galvanic skin responses etc) that makes them distort what they perceive.

This test turned out to be very useful. There was a high correlation (above 0.7) between the test points and inadequate behaviour or mistakes in demanding flight situations, which made it greatly superior to MMPI and other common psychological tests used in pilot selection.

The most important reason is that, differently from such tests, it does not depend on verbal responses to questions but is an objective detector of defense mechanisms.

The test reveals deep-seated disturbances

According to psychology, the proneness to use psychological defense mechanisms in threatening situations is closely related to the presence of deeply seated, often early acquired memories of anxiety-provoking or insecurity-causing experiences (they don’t need to be very dramatic from the viewpoint of grown-up people, because children may react very intensely to what may seem minor incidents). These memories uphold an increased level of conscious or often subconscious anxiety, called trait-anixety in psychology.

When a situation somehow appears threatening to such a person, this anxiety tends to break through. The defense mechanisms serve to suppress these anxiety provoking impressions. Because children have much more intense emotions than mature people, the experience of anxiety is very painful. Therefore they have a strong tendency to develop mechanisms that suppress anxiety-evoking perceptions.

Consequently, differently from secure and harmonious people who perceive the threat realistically and handle it adequately, the disturbed person immediately mobilizes reality-distorting defense mechanisms.

It is important to note that the defense mechanisms are often so strong that people are not even aware of having any anxiety at all, and they appear perfectly normal psychologically. This is a major reason why paper-pencil tests, like MMPI, where people are asked if they have anxiety-related symptoms, have turned out to be almost completely useless in pilot selection.

Actually, it is the experience in psychotherapy, that those who believe they are totally anxiety-free tend to be the most disturbed ones. It has been suggested that the reason is that they carry so painful anxiety-provoking memories that, in response, they have developed strong defense mechanisms to suppress the anxiety. So paradoxically, an anxious person may be more psychologically healthy than someone who seldom or never experiences any anxiety.

Great decrease of flight accidents with DMT-Neuman

In the Swedish Airforce, there has been a great decrease (to almost zero) of accidents and incidents caused by pilot mistakes since the introduction of the test in 1970 (1). Formerly, such pilot mistakes were the major cause for serious incidents and crashes, and there were 10-20 people or more killed every year because of this (to be fair, some other routines were changed concomitantly, but the flight security experts agree that DMT played a major role).

The same is the experience from the other air forces that now are using this test for selection of combat pilots

Furthermore, before DMT-Neuman was used for pilot selection, about 55-80% of the pilot trainees failed every year due to inappropriate flight behavior (making mistakes in stressful flight situations provoked by the teachers). But after the test was introduced, virtually no Swedish pilot trainee have been discarded for this reason, although the pilot trainers systematically expose them for the same “stress tests” in flight action that made a major part of trainees drop out formerly. For more about validity, see footnote 1.

Defense mechanisms are remarkably common

Experience from DMT-Neuman studies has objectively verified the experience of psychologists that most people with these disturbances behave normally, except for in threatening situations. Therefore, barring reliable detection methods, their presence in the population was greatly underestimated before DMT appeared.

Extensive testing using DMT indicates that a surprisingly small proportion of the population is free from such defense mechanism-activating disturbances (see footnote 2).

This concurs with experiences, especially from developmental psychology, that indicates that very few people (a few percent at most) have a high level of inner security. High inner security is associated with low trait anxiety and thus no propensity for using defense mechanisms.

DMT-Neuman should be used to select leading decision-makers

Considering that defense mechanisms are so common, and can have devastating effects on the judgment in critical situations, this test should be used for the selection of decision-makers.

This goes especially for people like governmental leaders and top executives who often have to make vital decisions under great stress. Under such circumstances, an anxiety-prone person is very likely to make fatal mistakes because of the reality-distorting effect of defense mechanisms.

There is a strong connection between the presence of Defense Mechanims and “Survival-Oriented-Behavior” (SOB). It brings about the suppression of higher cortical centers responsible for intelligence, judgment, and foresight, as well as responsible, honest and humane behaviour, see “Stress and mind”. In addition to testing defense mechanisms, DMT thus also serves as a test of the presence of SOB, which further aggravates the ability to realistically assess the situation under stress.

Therefore, in my opinion, DMT is a very valuable test for finding out if top executives and top leaders are capable of functioning in an intelligent, balanced and adequate way under stress. This test, could, for maximum reliability in the selection of key persons, be combined with a “brain imaging stress test”.


DMT testing: For more information about DMT, including testing, you can contact me at the following email address (I have no affiliation with the company doing the testing):

Acknowledgement: I want to thank Air Force Colonel Lieutenant Folke P Sandahl, who supervised the Air Force DMT development project, for checking and confirming the correctness of this manuscript and for valuable suggestions and advice.


1. The validity of Neuman’s interpretation method

Ulf Kragh, the inventor of DMT suggested the responses to subliminally presented threatening pictures could be interpreted as projections of psychological states of the subject. However it is difficult to reliably establish the psychological significance of a certain response.

Because of this, Neuman avoided any evaluation of psychological states with his version of DMT. His mission was to develop a stringent quantitative test for selection of Air Force pilots. The Air Force demanded it should have a high reliability and validity. To achieve this, Neuman found it was useful to just register the presence of Defense Mechanisms. The number of different Defense Mechanisms present and some other stringently quantifiable criteria were used for calculating test points.

In a systematic manner, Neumann developed his evaluation method, using mistakes in combat pilot performance as the criterium of validity. He arrived at a correlation above 0,7 between the test points and error-proneness in pilot performance. The validity of this method has been further confirmed in extensive practical use in the Swedish and other air forces.

Neuman did additional in-depth studies that further confirmed the validity of his method, demonstrating the connection between presence of defense mechanisms as revealed by his test and traumatic memories. Unfortunately, the Air Force decided these reports should be confidential as they revealed intimate personal details of the subjects, some of whom still are active in the Air Force.

In assessing anxiety he did not use projective psychology interpretations but objective criteria like galvanic skin responses.

Conclusion: While the Kragh system uses a projective test approach for assessing the psychological response with important uncertainities due to interpretation problems, DMT-Neuman is a scientifically stringent quantitative method determining the amount of defense mechanisms with a high level of validity and reliability.


2. A high proportion of the population appears to have trait anxiety

The Swedish Airforce submits about 700-800 air force pilot training applicants to testing every year. The proportion that has passed DMT without showing a dangerous propensity for using defense mechanisms has been about 1 on 30-40, that is about 2.5-3 %.

However, it must be pointed out that the applicants were not a random sample from the population. It consisted of persons interested in undergoing pilot training. To be eligible, they had to be approved for military service by the drafting organization, which dismisses a significant proportion every year, including pepople with behavioral disturbances, alcohol- and drug additiction and other problems. Also people with pronounced psychosomatic and stress-relatd disorders are eliminated.

Therefore, the applicants for pilot training are most probably, at an average, more healthy than the population in general. This indicates that the real proportion not having trait anxiety and the associated propensity for defense mechanisms is probably less than 2,5 %.



1. Sandahl, F.P.: The Defense Mechanism Test DMT as a Selection Instrument when Testing Applicants for Training as Military Pilots. Stockholm: Kungl Krigsvetenskapsakademiens Handlingar och Tidskrift (Proceedings and Journal of the Swedish Military Academy) nr 4, p 132-154, 1988.

2. Sandahl, F.P.: Inverkan av tm-utövning på neurotiseringsgrad. Stockholm: Läkartidningen (Journal of the Swedish Medical Association), vol 77, nr 34, p 2808 ff, 1980. (Swedish)

7 thoughts on “Defense Mechanism Test (DMT)

    1. Jaan Suurkula Post author

      Because the company doing DMT-testing changed its name, I was unable to find them in spite of thorough Google search. Finally I succeeded by searching people who worked at the company formerly. I will inform you personally.


    1. Jaan Suurkula Post author

      There are two versions of DMT.

      The one I recommend, DMT ad modum Neumann, has been used by the Swedish Airforce since over 35 years and the experiences are very good.

      However the ownership of the test, offered for non-military purposes has changed and I don’t know who owns it nnow. To help you, I have contacted the Swedish Airforce and hope to get an answer that I will forward to you.

      I advise you not to go for the original evaluation protocol developed by Ulf Kragh, professor of psychiatry at the University of Lund, Sweden. It uses a much less stringent methodology. Ulf Kragh suggested the responses to subliminally presented threatening pictures could be interpreted as projections of psychological states of the subject (he used it for studying psychotic cases). However it is difficult if not impossible to very reliably establish the psychological significance of a certain response.

      Differently from Kragh, Neuman avoided any subjective evaluation of psychological states with his version of DMT and just measured the number of defense mechanisms activated and some other easily measurable variables, with no subjective interpretation elements.

      Neumann’s approach turned out to be very successful. The correlation between test scores and strictly confirmed pilot mistakes under demanding flight condition was extraordinary for psychological tests (above .8). I think it is highly unlikely that the subjective interperational method of Kragh, which is based on controversial psychological theory, will come anywhere close to this.

      I have been suggesting that the airforce pilot selection test is called DMT-Neumann, because of said decisive difference. It is most unfortunate that this distinction has not been established, because it is the evaluation of the responses that determines the result in a decisive way.

      So in reality, DMT-Neumann is a different test in decisive respects, than DMT-Kragh.

      Considering the high validity and great success in practical application, I think there are all the reasons not to use any other variety than DMT-Neumann when it comes to measuring defense mechanisms.


      1. Franchesca Mitra

        So Dr, aside from pilots, to whom do you think this test would be applicable? We’re still college students and this is our first time to make a research. Actually defense mechanism is just one of our option for our topic. We’ve been thinking of a nice topic and respondents, and also a theory that will fit our study.

        By the way Dr. we really appreciate your help and advice. I hope you’ll get an answer from the Swedish Airforce. It would really help us a lot.

        I will get this chance to ask you also of topics about psychology that we could use on our thesis.

        Thank you again Dr. Suurkula!


  1. Jaan Suurkula Post author

    The Defense Mechanism Test is being used by the Swedish Air Force also for selecting people to other jobs that require the ability to stay calm and keep the mind clear under very demanding conditions. DMT is also used in a number of other Air Forces at least for pilot selection.

    In civilian contexts it has been used for the selection of business leaders with the motivation that an impaired sense of reality due to defense mechanisms brings about the risk for making inadequate decisions.

    DMT is actually valuable for any job where the ability to resist stress even under heavy pressure is important as well as where it is of great importance that you are capable of making correct decisions.

    As it indicates the presence of “SoB” I have been arguing in this blog that the test should be used for selecting all political leaders and all key decision makers in governmental organizations as well as private corporations.

    The text that followed here has been published as a blog, see
    Increased flight security with crash-proof pilots“.



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