Judgments of short time intervals following awakenings from different EEG stages of sleep

Abstract

Twenty subjects were awakened from EEG sleep stages 1-REM, 2, or 4 and tested on estimation, production, and reproduction of time intervals from 1 to 9 sees. A comparison group of 20 subjects was tested according to a similar schedule during the day, and oral temperature readings were obtained at the day sessions. All subjects were young male adults. Subjective time rate decreased to a minimum somewhat past the middle of the sleep period and increased in the morning with little change during the day and no differential association with EEG stage. A tendency toward indiscriminate responding was identified which increased more markedly during the night than the change in time rate and exhibited a minimum near noon. A constant response error was greater following awakenings from stage 2 than from stage 1-REM. Subjective time rate appears to follow a circadian variation which generally parallels the sleep and body temperature cycles but is not specifically dependent on body temperature or the particular EEG stage of sleep.