Effects of afternoon naps on physiological variables performance and self-reported activation.

Fluctuations in physiological variables resulting from naps and the relationship of these to previously studies changes in performance and subjective activation associated with napping were examined. The subjects were eighteen healthy male university students who habitually slept 1/2-2 hr in the afternoon. Measurements were obtained of our physiological variables, from a continuous 10-min auditory reaction time task and two factors of an Activation. Deactivation Adjective Checklist 20 min before and after a control condition and two electroencephalographically recorded afternoons of sleep. The experimental conditions comprised a 2-hr period of wakefulness, a 1/2 hr nap from 4.35-5.05 p.m., and a 2-hr nap from 3.05-5.05 p.m. Following each sleep treatment, when compared with the control condition, there were statistically significant shifts of improved reaction time performance, and elevated activation as reflected by the two self-report scales, inceased EEG frequency, heart rate, and electrodermal responses. The shifts of increased behavioral efficiency, subjective and physiological activation were approximately equivalent in extent between 2-hr and 1/2-hr naps. These findings indicate that besides the previously reported facilitation by naps of performance and mood, physiological activation is increased following accustomed episodes of afternoon sleep.