Temporal variation in the luminance level of stimuli displayed on a cathode-ray tube monitor:: effects on performance on a visual vigilance task

This paper assesses the extent to which the sensitivity decrement frequently observed in vigilance tasks is affected by temporal variations in the luminance level of the stimuli displayed on the screen of a cathode-ray tube (CRT) monitor. First, it was confirmed that the luminance of the stimuli displayed on the screen of the CRT monitor decreases substantially during the first hour after turning the monitor on, and then it remains quite stable. Second, an experiment was carried out in which participants performed a visual vigilance task at three different time periods within which the luminance of the stimuli displayed on the screen of a CRT monitor either decreased or remained stable. The results indicate that the vigilance decrement is modulated by temporal fluctuations of the luminance of the monitor screen, which is used to display the stimuli. However, the relationship between both variables is not simple: the largest sensitivity decrement was not associated with the largest luminance decrement, but to a medium luminance decrement.