Target Detection,Rifle Marksmanship,and Mood during Three Hours of Simulated Sentry Duty

The purpose of this study was to evaluate the effects of sentry duty time on the soldier's speed of detection of visually presented targets, his ability to hit targets (rifle marksmanship), and his mood. Prior to the test day, each of eight subjects was given five days of training on the Weaponeer Rifle Marksmanship Simulator and was familiarized with the targets to be presented during testing. The test session lasted three hours, during which time the subject assumed a standing foxhole position and monitored the target scene of the Weaponeer. The Weaponeer M16A1 modified rifle lay next to the subject at chest height. When a pop-up target appeared, the subject pressed a telegraph key, lifted the rifle, aimed, and fired at the target. Speed of target detection was measured in terms of the time required by the subject to press the telegraph key in response to the presentation of the target. Marksmanship was measured in terms of number of targets hit. Target detection time and rifle marksmanship were averaged every 30 minutes. At the end of the test session, the subject completed the Profile of Mood States rating scale. The results showed that target detection time deteriorated with time on sentry duty; impairments were not evident within the first hour but were clearly evident by 1.5 hours. Marksmanship remained constant over time; soldiers were just as accurate in hitting the targets at the end of the 3 hours of sentry duty as they were at the beginning. Whereas the soldier's predominant mood during baseline practice sessions was one of vigor, during sentry duty the predominant mood was one of fatigue. The results of this study suggest that sentry duty performance may be optimized if it is limited to one hour or less.