The Fog of War: Documenting Cognitive Decrements Associated with the Stress of Combat

Abstract : Anecdotal reports from military conflicts suggest that cognitive performance is severely degraded by the stress of combat. However, there is little objective information available to confirm these observations. Recently, the authors have had several unique opportunities to study cognitive function in warfighters engaged in exercises designed to simulate the stress of combat. These studies were conducted with two very different types of military volunteers. In one study, subjects were officers, with an average of 9 years of military service, who were members of an elite, operational U.S. Army unit, the 75th Ranger Regiment. In the other study, the participants were younger, mostly enlisted, trainees with only 3 years of military experience on average, and who were in training to determine whether they would qualify to join an elite U.S. Navy unit, the SEALS. The authors administered a variety of identical computer-based cognitive tests to both groups. They consistently observed that during stressful combat-like training, every aspect of cognitive function assessed was severely degraded compared to the subjects' own baseline, pre-stress performance. Relatively simple cognitive functions such as reaction time and vigilance were significantly impaired, as were more complex functions, including memory and logical reasoning. The magnitudes of the deficits were greater than those typically produced by alcohol intoxication or treatment with sedating drugs. Undoubtedly, such decrements would severely degrade operational effectiveness. Furthermore, it is likely that such cognitive decrements would be even greater during the stress of actual combat. War planners, doctrine developers, and warfighters, especially leaders, need to be aware that combat stress will result in extensive and severe deficits in cognitive performance.