A Multiple Processing Resource Explanation of the Subjective Dimensions of Operator Workload

155 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.Multiple measures of operator workload may dissociate, or fail to agree, for a given task. The goal of this study was to determine how workload as indexed by attentional resource demand could explain the attendant variance in a second measure of workload, subjective ratings. A multiple structure model of processing resources (Wickens, 1980) guided construction of experimental tasks of differential resource demand. Nineteen subjects performed these tasks singly and in all dual task combinations, with predictions derived from the model suggesting degrees of performance efficiency and workload. Subsequent to performance, subjects rendered both workload similarity ratings on all possible pairs of tasks and rated each task on specific attributes. Multidimensional scaling analysis of the similarity ratings produced three subjective dimensions of workload. These dimensions were explained by the resource demand predictions derived from the Wickens model and by the specific task attributes that had been rated. An additive clustering analysis of the same similarity data produced nine overlapping task clusters whose existence was explained by the same constructs. Three categories of data were collected to support the analysis of scaling dimensions and task clusters: task performance data, physiological measures of heart period variability taken during task performance, and subjective ratings of effort. These traditional measures of workload, when examined outside of the scaling and clustering solutions, revealed three dissociations. When comparing difficult single tasks to tasks time-shared with themselves, performance was equivalent but effort ratings reflected greater workload for the time-shared conditions. Second, when comparing the time-shared with self condition to tasks that were time-shared with dissimilar tasks, performance was better in the latter case but effort ratings were equivalent between the two. Third, for these same two groupings of tasks, workload as indexed by heart period variability was greater for the latter set but performance actually improved. These dissociations were explained by using the parameters of Wicken's multiple resource model, and recommendations to measure workload based upon amount and type of resource usage are presented.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD