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This study confirms and extends a recent finding by Finomore et al. (2006) that the Multiple Resources Questionnaire (MRQ; Boles & Adair, 2001) can be of effective value in assessing perceived mental workload in sustained attention or vigilance tasks. As in the earlier study, the MRQ was evaluated by comparing it against a standard measure of workload in vigilance research, the NASA-Task Load Index (NASA-TLX; Hart & Staveland, 1988), in its sensitivity to experimental factors known to influence task demand. The factors in this case were the sensory modality of signals-brief changes in the duration of pulsed auditory or visual stimuli-and event rate-stimulus pulses for inspection occurred at a slow rate of 5 events/min or a fast rate of 30 events/min. Both workload scales showed that the level of workload was substantial, and that workload was greater for the fast then slow event rate. The NASA-TLX indicated that workload was greater when monitoring visual than auditory stimuli. With the MRQ, the sensory modality of signals emerged as a moderator variable for event rate; the effects of event rate were restricted to visual signals. The MRQ also identified resource dimensions that were utilized in the vigilance tasks that are not included in the NASA-TLX-Manual, Short-Term Memory, Spatial Attentive, and Visual Temporal dimensions. Thus, the MRQ exhibited the properties of sensitivity and diagnosticity characteristic of a valid workload scale (O'Donnell & Eggemeier, 1986).The effects of sensory modality and event rate on the stress of sustained attention were also evaluated in this study via Dundee Stress State Questionnaire (DSSQ; Matthews et al., 2002). The level of distress was greater in the visual than the auditory condition and in the visual condition, the worry level interacted with event rate, being elevated in the slow event rate condition and diminished in the fast event rate condition. These results confirm previous findings that the sensory modality of signals is a critical factor in the stress of sustained attention (Warm, Matthews, & Finomore, 2008) and indicate that event rate also plays a role in that regard. |
