Using cerebral hemovelocity to measure workload in a complex vigilance task with display redundancy

Abstract

Command and Control (C2) operators are responsible for monitoring multiple communication channels for long periods of time. One of the potential drawbacks of this important role is that these operators can experience a high degree of mental workload. The manner in which critical information is presented can influence the intelligibility, and thus, the workload of these tasks. To date, visual and auditory presentation of communication has been the primary focus of exploration regarding the manner in which critical information is disseminated to C2 operators. However, this research exploring auditory or visual only displays has been unsuccessful in preventing a performance decrement. Redundant displays may provide a solution. In this study, 45 operators monitored for the presence of critical phrases during a 40-min vigilance session with 1 of 3 different displays: auditory only, visual only, or a display with redundant auditory and visual information. Workload was measured using cerebral blood flow velocity (CBFV) and the NASA-TLX. Performance accuracy results revealed that the redundant display and visual only display facilitated more accurate performance than the auditory only condition, and that reaction times were faster for the redundant display condition than the visual only condition. Results pertaining to the physiological measure revealed that CBFV declined significantly over time, and a three way hemisphere x period x display condition interaction revealed that both hemispheres experienced a decrement in the visual and auditory conditions, but this effect was lateralized to the right hemisphere for redundant display conditions. Workload ratings from the NASA-TLX were insensitive to differences in workload for the different display conditions. Results are interpreted in terms of a resource model of vigilance performance and the cerebral lateralization of vigilance tasks.