| Abstract: | Variability of sleep measures during 4 nights was examined in 10 normal young adults. The variables analyzed included: Sleep Stage Percentages; Sleep Time; Latency, Duration, and Cycle Time of REM; No. of REM Periods; and No. of Eye Movements (EM). No indication of First Night Effect was found, except that EM showed significant increases across nights. Although group means corresponded to conventional norms, considerable inter- and intraindividual variability was apparent, with Stage 2 and REM yielding lowest Variability Coefficients. Between nights, consistent positive correlations were found for Awake, REM, REM Latency, and particularly for Stage 4 and EM. Consistency of the relationship between nights for the sleep stages was not generally improved by equating sleep time either within or between Ss. Few intercorrelations between variables were significant. Within nights the first REM Duration was the shortest and the first Non-REM Duration the longest, while neither REM nor Non-REM Cycle Time changed significantly. In 25% of the records, Stage 3 terminated before Stage 4. Variability was discussed in terms of procedural aspects, trait characteristics, and situational factors. |
