Effects of Spatial Uncertainty on Tactile Vigilance

We examined effects of task demand on tactile vigilance by manipulating spatial uncertainty, which has been shown to affect visual vigilance. While holding a tactor in each hand, participants received a long or short (critical) vibration, and pressed a foot pedal when the critical stimulus occurred. In the “certain” condition, the spatial location of the stimulus alternated predictably across hands. In the “uncertain” condition, the stimulus was randomly assigned to either hand. We measured response time; proportion hits and false alarms; sensitivity and response bias; and stress and workload. Vigilance decrement was observed; sensitivity decreased and response time increased. Spatial uncertainty did not affect the occurrence or magnitude of the decrement. Results suggest that effects of cognitive demands are more similar between tactile and auditory modalities compared to the visual modality. Interface designers should be aware that spatial uncertainty likely has more detrimental effects on visual vigilance, compared to tactile vigilance.