EFFECTS OF CONTROL ORDER, AUGMENTED FEEDBACK, INPUT DEVICE AND PRACTICE ON TRACKING PERFORMANCE AND PERCEIVED WORKLOAD

Virtual interfaces to advanced human-machine systems will present oper ators with a variety of perceptual-motor challenges. To inform the vir tual interface design processes, the present experiments examined the effects of track order, level of knowledge of performance, type of con trol device, and the extent of practice on tracking performance and as sociated mental workload. Tracking was assessed by root mean square er ror. Subjective workload was measured using both the NASA Task Load In dex (TLX) and the Subjective Workload Assessment Technique (SWAT), Res ults indicated non-linear effects, where tracking error and subjective workload both increased non-proportionally with track order. Trackbal l use resulted in more accurate performance and was judged to be of lo wer subjective workload than input using a mouse. Augmented knowledge of performance had little effect on either performance or workload. Th ere were a number of interactions affecting performance that were repl icated in perceived workload. Over acquisition trials, second-order tr acking exhibited continuous improvement. This capability was retained even after a 30-day rest interval. Decrease in workload followed perfo rmance improvement in both initial acquisition and subsequent retentio n phases. The two subjective workload scales were essentially equivale nt in terms of their sensitivity to task manipulations. These results support the direct association between workload and performance and co nfirms the use of workload in helping to evaluate the influence of div erse task-related demands. The implications for the design of virtual interfaces to real-world systems are examined in the light of these fi ndings.