United States Department of Transportation
i
Blinks, saccades, and fixation pauses during vigilance task performance. II., Gender and time of day.
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1996-03-01
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[PDF-2.19 MB]
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Abstract:As operators are required to spend more time monitoring computer controlled devices in future systems, it is critical to define the task and situational factors (i.e., fatigue) that may impact vigilance and performance. Aspects of the gaze system can be monitored relatively unobtrusively, although we used conventional electro-oculographic techniques in this study. Can gaze control measures be used to reflect, and hopefully predict, periods of impaired attention and performance? Gaze control measures (blinks, saccades, and fixations) were recorded while subjects performed on an air traffic control simulation task. Twenty-five subjects performed the task for 3 days at 2 successive hours per day. Blinks and saccades were sampled for 5 consecutive minutes after 10,30, 50, 70, 90, and 110 minutes of task performance. Significant Time-On-Task (TOT) effects were obtained for all of the 13 variables abstracted. A number of main effects for DAY and a number of interactions involving DAY were significant. TOT effects were obtained for blink rate, blink closing duration, 50% window, blink amplitude, long closure duration blinks, eye closure frequency, blink flurry frequency, number of blinks part of flurries, saccade rate, saccade amplitude, fixation duration, long duration fixations, and performance decrements.
The changes in blink frequency and other blink attributes are interpreted within a framework suggesting a breakdown of inhibitory control as a function of TOT. We believe that this TOT effect is not a tonic one, i.e., a steady decline in the ability to inhibit, but a phasic process, in that periods of poorer inhibitory control increase in frequency and duration as a function of TOT. This conceptual model is akin to one proposed by Bills (1931) dealing with performance "blocks."
Performance declined as a function of TOT but improved over days of task performance. This improvement is mirrored by changes in blink parameters, suggesting that the task had become easier to perform.
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