Effect of Sensory Modality on Performance Workload and Frontal Lobe Oxygenation in a Standard Vigilance Task

Performance, subjective workload, and frontal lobe oxygenation measures were collected from observers monitoring visual, auditory, or vibrotactile signals. Critical signals for detection in each sensory modality were stimuli of reduced duration, which were equated for perceptual salience and discriminability. Perceptual sensitivity to targets and the percentage of correct detections declined significantly over time for all sensory modalities, with significantly greater performance decrements for the visual modality than for the auditory and tactile modalities. Frontal lobe oxygenation, as recorded by functional near infrared spectroscopy 0NIR), increased over time in task conditions as compared to a control (no work imperative) condition, but no significant differences in oxygenation were found between modalities in the active monitoring conditions. Likewise, subjective workload was significantly higher for task conditions versus the control condition, and for the visual condition versus the auditory and tactile conditions. The results are consistent with Hatfield and Loeb's (1968) theory of coupling with display type determining differences in vigilance performance over time. Oxygenation data suggest that vigilance may not be sensory-modality specific, but a unitary process, and suggest oxygenation is sensitive to task difficulty.