TECHNIQUES OF SUBJECTIVE WORKLOAD ASSESSMENT: A COMPARISON OF SWAT AND THE NASA-BIPOLAR METHODS

Abstract Assessment of subjective workload is becoming increasingly important in the evaluation of human-machine systems. Two popular methods were compared: (1) the Subjective Workload Assessment Technique (SWAT) that employed a conjoint measurement procedure to confer interval scale properties on the workload ratings, and (2) a technique under development at NASA that used an individually weighted workload score. Both methods were applied in a laboratory experiment that required the rating of a number of single- and dual-tracking and spatial transformation tasks. Both subjective assessment techniques displayed similar sensitivity to the different task manipulations. However, both techniques failed to detect the resource competition effects in the dual-task performance, and were in general insensitive to response execution processing demands. A notable difference between the two techniques was that the NASA-Bipolar ratings consistently had a smaller between-subject variability than the SWAT ratings. Discu...