The effect of event rate on sustained attention and stress states in a simultaneous vigilance task paradigm

See, Howe, Warm, and Dember (1995) performed a meta-analysis on previous studies of vigilance. Their results suggested that manipulating the following variables produced sensory decrements in vigilance tasks: discrimination task type (simultaneous versus successive), event rate (low versus high), and stimulus type (sensory versus cognitive). The aim of the present study was to examine one of these variables, namely event rate. Specifically, the study assessed the effects of varying levels of event rate on vigilance performance using a sensory simultaneous vigilance task paradigm. A further aim of the study was to understand the effects of task demands on vigilance performance. Resource theory contends that performance on vigilance tasks decreases as task demands increase; and that attentional resources are drained under high task demand conditions (Wickens, 1984). In contrast, Hancock and Warm (1989) argued that levels of both low and high task demands can have a negative impact on performance, resulting in conditions of underload and overload, respectively. Our results suggest that observers experience conditions of overload as task demands (i.e., event rate) increase. Observers, however, did not experience conditions of underload as task demands (i.e., event rate) decreased. These results are consistent with Resource Theory (Wickens, 1984) rather than the Adaptation Model (Hancock & Warm, 1989). Additional results are discussed in relation to the See et al. (1995) meta-analysis and the effect of event rate on stress states. Such results have both theoretical and practical implications.