Effects of task demands on tactile vigilance.

A performance decline during sustained monitoring of unpredictable and occasional signals, the vigilance decrement, has been studied mostly in the visual and auditory modalities, but a tactile vigilance decrement also has been observed and has been associated with high perceived workload, declines in sensitivity and task engagement, and increases in distress. The primary aim of the current study was to determine whether task demands affect the vigilance decrement in the tactile modality and whether the effects are similar to those observed in the auditory and visual modalities. Participants completed a 40-min vigil in which they monitored vibrotactile stimuli generated by a tactor and had to discriminate between durations of bursts of vibrations. Task demand was varied by including low and high event rates. Although correct detections decreased over time (vigilance decrement) and sensitivity was greater for the slower event rate, there was not an interaction between period of watch and event rate. There also were no differences in workload and stress between event rates. Results indicate that mean performance in tactile vigilance tasks is negatively impacted by increases in event rate, indicating that a typical source of task demand known to affect visual and auditory vigilance also affects tactile vigilance. Results could be explained by either an underload or overload theory of the vigilance decrement.