Field Assessment of Cognitive Performance under Stress

Abstract

Performance decrements have frequently been reported in combat but it has been difficult to demonstrate the specific causal source of cognitive degradation sufficient to disrupt performance during military operations. In the present study, seventeen infantrymen were assessed during both a one-week simulated combat exercise and a pre-dawn assault. Significant change did not occur during the one week exercise, however simple reaction time did increase following the assault. One planned field assessment occurred at the moment following a potentially serious medical event. A soldier perceived that he was experiencing heatstroke but medical evaluation indicated that he was still “fit for duty”. Cognitive evaluation of his failing state was characterized by slow Simple Response Time and rapid and inaccurate responding on more complex response tasks. Fortunately, the soldier could return to duty but his scores slowly recovered, such that he returned to baseline levels two days later. The present infantry operational environment did not produce significant-information processing change in infantrymen. However, significant performance cognitive decrements followed the specific acute event of assault that was perceived as life-threatening. As we demonstrate, increased reaction time after the assault is consistent with increased fatigue following an extended period in the infantry operating environment.