Abstract
The Kragh tachistoscopic method for measuring psychological defense mechanisms (“Defense Mechanism Test” - DMT) has been claimed to be valid for selection of personnel for really dangerous tasks. The method consists of presenting a stimulus picture at initial exposure times that are too short for perception. To test whether this perceptual disturbance arises from an aberrant cognitive response to the situation, we studied the magnitude, topographic distribution, and temporal modulation of spectral density in the 8–12 Hz EEG frequency band during DMT testing in 22 male and 2 female active duty US Air Force personnel. Personnel with high defense mechanisms had significantly more attenuation of the 8–12 Hz activity during stimulus exposure than low defenders, implying an increased level of cortical activation. Personnel with low defense scores relax faster than those with high scores. The differences seem to occur even before threat is reported. High defense seems to require more and longer lasting data processing which may be too costly in dangerous situations.
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