Influence of task demand characteristics on workload and performance.

Two experiments are reported that examined the influence of variation in task demand on performance and workload. The first experiment considered how the manipulation of prior level of task demand affected subsequent workload and performance. The second experiment examined the effects on performance and workload of increments in the level of task demand. Results from the first study indicated that prior level of imposed task difficulty did affect response in a manner consistent with a scaling of workload in relation to previous task conditions. The second study demonstrated the primacy of absolute demand level over increments in that demand as influencing operator response. Overall, our results indicate that workload and performance are sensitive to multiple characteristics of the task and not instantaneous demand level alone. These findings are important in explaining why association and dissociation occur between task demand, operator efficiency, and perceived workload in differing performance contexts. The importance of these findings for the aviation psychologist in assessing pilot and operator workload is articulated.