Antecedents of sleep.

Abstract

Evidence of a decrease in sleep latencies was found in white rats over 17 days when they were tested daily in the same environment after 5 hr. of sleep deprivation. However, the terminal latencies did not differ from the latencies of Ss treated similarly but not permitted to sleep in the test environment. There was a relationship between sleep deprivation periods of 0, 2 1/2, 10, 15, 20, 25, and 30 hr. and sleep latency, although this effect was not marked. No significant difference was obtained between sleep latencies after 30 hr. of food deprivation versus those after no food deprivation. Throughout the experiments, a marked individual consistency in latencies of going to sleep was noted across all of the conditions of the experiment. Furthermore, the major determinants of sleep latency were individual differences in contrast to the conditions imposed on these Ss (past experience, time of sleep deprivation, and an irrelevant hunger drive). Further observations suggested that the time to sleep may be jointly determined by a development of wakefulness tendencies as well as sleep tendencies.