On circadian variations in discrimination of duration.

TLDR: No significant effect of time of day could be demonstrated, indicating that circadian influences on time perception in the range of milliseconds are less evident than on the time estimations in therange of seconds or other psychophysiological functions.

Abstract: Evidence from numerous studies indicates that physiological processes, e.g., body temperature, hormonal activity, as well as mental and psychomotor performance, e.g. memory, vigilance, reaction time, vary systematically with cime of day (Minors & Waterhouse, 1981). Also, time of day has been shown to influence time judgments of intervals ranging from 10 to 60 sec. studied by means of the method of production and verbal estimation. These result in most pronounced underestimation in the morning hours and fastest production of instructed time intervals and verbal overestimation between 1 p.m. and 4 p.m. (Pfaff, 1968). No studies have investigated the effects of cime of day on perception of shorter intervals in the range of milliseconds. The present study was designed to test circadian variation of this type of performance. Thirty-six graduate students (16 men and 20 women) were divided into two groups matched for age and sex: a morning group tested between 9 a.m. and 11 a.m. and an afternoon group tesced becween 1 p.m. and 3 p.m. In a forced-choice version of the method of comparison, subjects had to decide which of two acoustic stimulus intervals, marked by two consecutive 3-msec. clicks each, was the longer one. With the standard duration of 50 msec. presented first, each comparative duration (35, 40, 45, 55, 60, and 65 msec., respectively) was presented 50 times in randomized order resulting in 300 judgements of relative duration. As a measure of performance, probability of correct responses was computed for each subject. Data were analyzed by analysis of variance. Means and standard deviations of probability of correct responses for the morning group were 0.76 and 0.13 and for the afternoon group were 0.78 and 0.13. No significant effect of time of day could be demonstrated (F,,,, =0.07, p> .lo), indicating that circadian influences on time perception in the range of milliseconds are less evident than on the time estimations in the range of seconds or other psychophysiological functions. Furthermore, these results suggest that there may be different underlying mechanisms of time estimation in the range of seconds and discrimination of duration in the range of milliseconds.