Abstract
The primary focus of much of the workload research over the years has been the sensitivity of the mental workload measures to changes in task demands. However, as Wickens (1984) hypothesizes, the construct of workload is, in actuality, an interaction between the supply of operator mental resources available to devote to a task and to the demands of that task (i.e., “residual capacity”). Therefore, workload fluctuations can occur from either changes in operator capacity or changes in task demand.
A study was performed to investigate the interactive effects of workload induced by changes in task difficulty, fatigue induced by time-on-task and fatigue induced by sleep deprivation on pilot performance. The focus of the current paper is on a finding that Subjective Workload Assessment Technique (SWAT) varied reliably for both the main effects of time-on-task and sleep deprivation, as well as for task difficulty. This finding indicates that SWAT, and probably subjective measures in general, are sensitive to workload induced by changes in operator capacity induced by fatigue. Implications of this finding for workload measurement in general are discussed.
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