A Model of Human Response to Workload Stress

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When faced with decreased time to complete a task, operators often hold performance constant. When workload is excessive, this is not possible and operators may speed work and ignore errors or fail to finish the task. In this experiment, we forced a choice among policies by decreasing time allowed for a task until it could not be completed. Operators established a baseline time to perform a standard task, and times were decreased to 80%, 60%, 50%, 40%, and 30% of this baseline. Operators were able to decrease time per subtask by 20%, but no further decreases were observed as time demands increased. Errors remained constant over all conditions. The data support the view that increases in task demand produce increases in resources that are adequate for small demand increases but insufficient for great task demands.



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