A Model for Mental Workload in Tasks Requiring Continuous Information Processing

Abstract

INTRODUCTION The object of this paper is to define and justify a model for mental workload that is appropriate to tasks in which a human operator is required to process sensory information in a continuous fashion. The primary application of this model has been to continuous manual tracking tasks, although certain non-tracking tasks are also candidates for application. The model appears to be most useful as a design and evaluation tool for predicting the relationship between performance and workload; measurements of workload using concepts suggested by the model can be obtained only under highly constrained situations. In this paper we define workload not in physiological terms but in terms of a performance characteristic of the human operator Specifically, workload is related to the relative amount of randomness in the human operator's information processing activity where decreasing randomness is associated with increasing mental effort. Since operator randomness can be associated with a parameter of an existing model for human operator behavior, analytic predictions of performance/workload tradeoffs can be obtained. The terms ''attention" and "workload" are both used in this treatment. It is perhaps natural to consider "attention" as a level of mental effort voluntarily committed to a task, and "workload" as a level of mental effort required by the task. For purposes of model development, the terms are used interchangeably (i.e. the degree of voluntarism is irrelevant to the mathematics of the problem).