ABSTRACT
Decrements over time in sustained attention (vigilance decrement) have been attributed to filtering, reduced tonic arousal, neural habituation, and related factors. A recent taxonomic approach to vigilance suggests that multiple factors may play a role in vigilance decrement. Furthermore, the factors that account for performance changes over time (vigilance decrement) may differ from those influencing the overall level of performance (vigilance level). This chapter examines the role of four factors—tonic arousal, capacity limitations, target expectancy, and neural habituation—in the explanation of the vigilance decrement and the level of vigilance. The results of three experiments suggest a multifactor model of sustained attention in which the level of vigilance is related to tonic arousal, and the vigilance decrement to expectancy or capacity, depending on the event rate and other task parameters defining different classes of vigilance task. Arousal and neural habituation do not appear to play a significant role in vigilance decrement.
