Friend-Foe Discrimination, Caffeine, and Sentry Duty

Abstract

In war, the sentry must continually and rapidly detect targets, correctly discriminate friend from foe, and shoot with accuracy. Past research shows that caffeine enhances the sentry's target detection speed when all targets are foes. This study evaluates sentry performance when friend-foe discrimination is required. Eleven men and 11 women participated in four simulated sentry duty sessions lasting 3 hours each: (a) 200 mg caffeine, foe-only; (b) 200 mg caffeine, friend-foe; (c) placebo, foe-only; and (d) placebo, friend-foe. Participants monitored the target scene of the Weaponeer Rifle Marksmanship Simulator with instructions to fire at enemy targets. Without impairing marksmanship, 200 mg caffeine reduced friend-foe discrimination errors and eliminated the decrement in target detection speed associated with time on the task. Men were likely to commit friendly-fire errors (shoot at friendly targets) and women were likely to commit fail-to-fire errors (fail to shoot at enemy targets).