Maintenance of vigilance by non-task-related stimulation in the monitoring environment

The effects of non-task-related stimulation on the performance of a simple visual vigilance task were investigated. 40 subjects monitored a stimulated CRT display for two 90-min sessions. The independent variables were variable vs constant intensity lighting and variable vs constant intensity noise. Probability of detection was not significantly different for the noise conditions; however, probability of detection was significantly higher under variable than under constant intensity lighting.