Measuring Mental Workload: Problems, Progress, and Promises

An overview is given of the problems of defining, quantifying, and measuring mental workload during interactive human/machine tasks, based on the author's work in the areas of: aircraft handling qualities; human operator modelling, measurement, and prediction; multi-display scanning; and psychophysiological correlates of mental workload. The frustrating cycle of promises–then–problems with psychophysiological measures of mental effort is assessed, and the importance of workload rating techniques is emphasized. The lack of a unifying theoretical approach is identified as the main impediment to progress, and an approach is suggested that can handle both continuous and discrete task loads. A review is given of some “new” (c 1980) workload measurement concepts such as: multi-dimensional ratings, the “imbedded surrogate” auxiliary task method, and the measurement of “workload margin” via the Cross-Coupled-Instability Task (CCIT).

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