Shiftwork and Performance

The recent increase in the incidence of shiftwork has been accompanied by a change in the type of task typically performed by the shiftworker. The technological advances which have produced both these effects have meant that the shiftworker is more likely to be engaged in cognitive, mentally taxing tasks than the predominantly perceptual-motor ones typical of earlier times. Contemporary research on time of day effects in performance efficiency has indicated that these task changes may be crucially important in determining on-shift performance, and hence the choice of the individual and shift system that is most suitable. Evidence is reviewed on task demands, the effects of different shift systems, and the role of individual differences. A descriptive model is proposed in which on-shift performance is seen to be dependent on the type of task, type of shift system, and type of person, with the three factors interacting via the worker's various circadian rhythms.