ON ADAPTIVE-CONTROL, SLEEP LOSS, AND FATIGUE

This paper considers the relationship between levels of control and st ressors put forward by Broadbent in Decision and Stress. Broadbent spe culated that a lower level of control could be maintained in an optima l state by the activity of an upper level such that performance outcom es remained constant. The upper level, however, could become fatigued, allowing any inefficiency of the lower to be reflected in performance . He thought that lower inefficiency was a function of sleep deprivati on, among other stressors. To illustrate the ideas put forward by Broa dbent, preliminary results from an extended study of the effects of va rying amounts of sleep deprivation and length of work day on an adapti ve control task are presented, with the aim of exploring the value and limitation of the levels approach. The adaptive control task used is one developed by Broadbent to explore levels of control. The paper con siders how levels of control could relate to behavioural outcomes of ' performance level' and 'work rate' under conditions of sleep loss and fatigue, and discusses some of the advantages and disadvantages of so doing. We conclude that the levels of control approach offers a potent ially rich interpretive framework for the effects of stressors on perf ormance, but that attempting to relate particular performance indices to particular levels is a less fruitful diagnostic endeavour.