Abstract
Performance often degrades over time in a vigilance task where an operator must identify critical signals. An extensive effort has been made to determine the mechanism underlying this vigilance decrement. Sustained demand theory proposes that high attentional demand sustained over the course of the vigil extracts a toll in fatigue, leading to the decrement. However, since an observer typically searches for one consistent target in a vigilance situation, results from dual-processing studies would suggest that automatic processing (Schneider & Shiffrin, 1977) should develop over time, and performance should improve rather than degrade. The purpose of this study was to identify the role of automatic and controlled processing within and across vigilance sessions. High memory loads led to an attenuation of the vigilance decrement, a result inconsistent with sustained demand theory. Low memory loads produced results more consistent with a sustained demand interpretation. Implications of these findings for a theoretical account of the vigilance decrement are discussed.
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