The Rate of Gain of Perceived Workload in Sustained Attention

Abstract

Perceived workload was measured via the NASA TLX following a visual vigilance task. Five task durations (10, 20, 30, 40, or 50 min) were combined factorially with two levels of discrimination difficulty (easy, hard) in a between groups design. Detection probability, computed from the final 10 min of watch in each duration condition, varied inversely with signal salience and declined over time. Overall workload varied directly with salience and increased linearly over time. The temporal growth in perceived workload was independent of signal salience. This result suggests that the rate of gain in workload is based upon general features of the vigilance situation rather than specific psychophysical demands such as signal salience.

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