and

The utility of a new measure of perceived mental workload in vigilance, The Multiple Resources Questionnaire (MRQ), was evaluated by comparing its sensitivity against that of the standard measure in this area, the NASA-TLX. Sensitivity was assessed in regard to the effects of a factor previously shown by the NASA-TLX to affect task demand, detecting stimulus presence/absence. Performance efficiency was significantly greater when critical signals for detection were defined by the presence of a target feature than by the absence of that feature. This effect was echoed in higher global workload scores for absence than presence when workload was measured by the NASA-TLX and by a modified version of the MRQ involving an increase in the response range for each item in the scale. Additionally, the MRQ identified resources utilized in the vigilance task that are not reflected in the standard measure. The results indicate that the new scale could be a useful adjunct to the older one. Vigilance or sustained attention tasks require observers to maintain their focus of attention and to detect transient and infrequent signals over prolonged periods of time. The monotonous and repetitive nature of vigilance tasks has led to a long-standing belief that they are understimulating work assignments that impose little information processing demand upon observers and the belief that observers perform these tasks in a thoughtless, routinized manner (Nachreiner &amp