Search Differences for the Presence and Absence of Features in Sustained Attention

Abstract

The present study examined the ability of individuals to look for the presence or absence of stimulus features in a vigilance paradigm. Forty participants monitored a computer display comprised of either 2 or 5 circles for 40 min. Half of the participants were instructed to respond when a line was present in one of the circles, and the other half responded when the line was absent from one of the circles. Although performance declined throughout the vigil in all conditions, the overall level of performance was dependent upon both display size and type of signal. Specifically, performance was worse when searching for the absence as opposed to the presence of the feature, and this effect was exacerbated with the five-stimulus display. On the other hand, display size had no effect when searching for the presence of the feature. These results are discussed with respect to the feature integration theory and the nature of the critical signal in vigilance.