Effect of Presenting Novel Verbal Material during Slow-wave Sleep

Abstract

THE topic of sleep learning has come increasingly to the fore during the past decade, partly because of the considerable scientific interest that has been shown in the Soviet Union, where a number of unusual claims have been made^1–3, and also because of the growing commercial interest in marketing devices designed to enable individuals to make use of the supposedly “waste periods” of sleep by storing useful, if perhaps dull and repetitive, material while in a state of unconsciousness. In principle the idea is attractive, but it depends on at least two assumptions: (1) that during sleep no other important process is taking place which would be disrupted by input of data; (2) that it is indeed possible for the brain to store (and subsequently extract) information fed in during those periods of sleep known as levels C to E⁴, during which consciousness is generally believed to be absent. The function of sleep is still largely not understood, but present evidence suggests that important information processing may be taking place at frequent periods throughout the night. Experimental evidence for the second assumption is contradictory^5–7 and often obscure. Fox and Robbin⁵, for example, seem to have obtained clear-cut evidence for “sleep learning” (of Chinese–English equivalents) but their experiment is open to criticism because the subjects were not actually observed while the material was being fed in and it is possible that the learning took place when the subjects were at least partially awake.