Effects of Auxillary Load on Vigilance Performance in a Simulated Work Environment

The effects of extra-task demands and long hours of work on the performance of simultaneous (comparative judgment) and successive (absolute judgment) type vigilance tasks were assessed in a simulated work environment. For three consecutive 12 hour days, subjects engaged in four 1-hour vigilance sessions interspersed with work at a heavy-load (20 codes/rain) or a light-load (10 codes/min) data entry task. For both types of vigilance tasks, performance efficiency varied inversely with the auxilary workload confronting the subjects. In addition, the quality of vigilance performance improved over the work week in the context of the light auxilary workload and declined in the context of the heavy load. Subjects reported becoming more drowsy, strained and fatigued and experienced more somatic complaints over the work day and the work week. These mood effects were maximal with the successive task and a heavy auxiliary workload, suggesting that in order to maintain performance standards in the successive task, subjects expended more processing resources which led to a greater cost in fatigue and strain.