Sustained performance and some effects on the design and operation of complex systems

Man, increasingly the limiting element in the military man-machine system, must often operate for several days in a high-risk environment with little or no sleep. It is necessary, therefore, to have some knowledge of the likely effects of sleep deprivation to predict his behaviour and minimize the adverse effects of sleep loss. The early work of the Army Personnel Research Establishment (APRE) concentrated on studying the infantryman in field trials, characterized by more realism and of greater length than previously attempted. Although measures of cognitive functioning were included in these trials, continuous cognitive performance was not assessed, nor was performance on complex tasks. An opportunity to remedy this situation arose because of a newer study concerned with controlling a removely-piloted air vehicle from a ground control station (GCS). A 65-hour experiment was designed during which subjects performed continuously either on the GCS simulator or on a battery of cognitive tests, mood scales, and physiological assessments. Results showed that whereas performance showed the usual deterioration in the test battery, it held up remarkably well on the simulator. Several reasons for this difference are suggested.