The effect of visual taskload on critical flicker frequency (CFF) change during performance of a complex monitoring task

Abstract

Abstract : The present study examined the effect of differing levels of visual taskload on critical flicker frequency (CFF) change during performance of a complex monitoring task. The task employed was designed to functionally simulate the general task characteristics of future, highly automated air traffic control systems in which passive monitoring is likely to be a principal job requirement. Forty subjects, divided into two equal-size groups, monitored displays containing either 8 or 16 alphanumeric targets. Nine critical events were randomly presented during each half-hour of the single 2-h session to which each subject was exposed. CFF thresholds were obtained prior to and following the sessions. Subjects monitored for the occurrence of two types of critical events. The first type consisted of a readily detectable change in an alphanumeric data block; the second kind of event was the occurrence of two aircraft (alphanumeric targets) at the same altitude on the same flight path. The results revealed that the more readily detectable critical events showed no evidence of performance decrement at either level of visual taskload. For the more difficult task of detecting critical altitude events, both CFF and performance showed evidences of fatigue that were confined entirely to the higher taskload condition. The findings are discussed with reference to fatigue and monitoring loads in highly automated air traffic control system concepts.