ULTRADIAN RHYTHMS OF REACTION-TIMES IN PERFORMANCE IN VIGILANCE TASKS

This study examined the presence of rhythmic fluctuations in vigilance tasks. The hypothesis was that individual attentional performance is subject to rhythmic variation beyond a linear decrease over time. In t he first study the reaction times to an acoustic stimulus were recorde d. The analysis of the individual periodograms indicated a rhythm in a ttentional capacity with periods ranging from 5 to 30 min. These findi ngs indicate that considerable individual variation can be accounted f or by considering individual periodicity in performance. Although mark ed individual differences between subjects are present, the rhythmic f luctuations are stable within each subject and between experimental se ssions.