With the advent of digital avionics and cathode ray tube (CRT) displays, the use of computer-generated flight displays has become increasingly prevalent in both commercial and military cockpits. These flight displays, however, typically are renditions of the electromechanical displays that are being replaced. But there is great potential for display enhancement and integration through formats such as pictorial, real-world formats that could enhance situation awareness and reduce crew workload. This study had as its objective the exploration of workload measures in conjunction with a larger study of a computer-generated, integrated pictorial primary flight display presented in stereo and non-stereo modes. Of interest in the workload aspect of the study was the ability to differentiate workload attendant with use of several versions of the pictorial display having alternate implementations of 3-D symbology cues, presented in stereo and non-stereo modes. Both physiological and subjective measures were used with a pilot-in-the-loop flight simulation task. The physiological measure was visually-evoked brain wave potentials; the subjectve measure was the Subjective Workload Assessment Technique (SWAT) (Reid, Shingledecker, and Eggemeier, 1981a and Reid, Shingledecker, Clark, and Eggemeier, 1981b). A number of physiological studies have demonstrated the relationship of the P300 component of event-related brain potentials to controlled stimuli (e.g., Zacharias, 1988). Further physiological studies by Kramer, Donchin, and Wickens (In Press) have shown that the amplitude of the P300 can be related to levels of pilot workload. The SWAT is a validated measure of subjective workload. Nataupsky and Abbott (1987) used SWAT to differentiate levels of a pilot's perception of workload in a piloted simulator flight task. The workload portion of the study was accomplished in the following manner. Pilots were initialized on the nominal flight path (as defined within the pictorial display). After approximately 2 seconds, they were suddenly offset to one of eight positions. The sudden display shift was the stimulus to which pilots had been asked to respond with control inputs and was the trigger for the visually-evoked response. Thus, contrary to previous studies conducted at Langley which used secondary tasks to elicit evoked potentials, this study had the primary task as the trigger for the evoked response. The pilots' task was to make the initial pitch and/or roll input necessary to correct back to the nominal flight path. Data was collected on 216 trials for each of eight Air Force pilots. Analysis of the workload data is in progress.
Investigating the validity of subjective workload rating (NASA TLX) and subjective situation awareness rating (SART) for cognitively complex human–machine work
