Performance after awakening at different times of night

Abstract

Naval ratings were roused during the night and presented themselves, dressed, for testing in a nearby room within 4 min. During the next 11 min, they were given tests of reaction time, calculation, and muscular coordination and steadiness. In all three tests, performance was well below the normal level achieved during the day. On different occasions, the men were roused at different times of night, and this factor influenced which task was affected most. Reaction time, with its intermittent call for rapid response, was impaired most in the early part of the night; the adding and coordination tasks, which demanded more continuous performance, were more affected later in the night. It is suggested that the early effects may be due to the depth of the preceding sleep, while the later ones may be influenced more by the trough in the circadian cycle of physiological activity.