[Dynamics of operator's efficiency under the condition of long continuous vigil]

Chambered male test-subjects (n = 8) kept awake over 72 hours. Every one or two hours during the initial 67 hours they did a tracking test that took 10 to 15 minutes. The test required intense tracking of rhythmic light spots with unpredictably varying frequency and pressing the button as the frequency changed. Time of latent reaction was determined. The variable was shown to extend with the confinement and fluctuate with the period of approx. 28 hours. Average values on the first sleepless night was longer than the ones on the previous day in all subjects with personal difference ranging from 7 to 37% and averaging 21%. That is, on the first night everyone was less efficient as compared with the previous day which could be excused by fatigue and natural variations in mental efficiency known to rise in the day and reduce in the night hours.