Responses to material presented during various levels of sleep.

Ninety-six questions and answers were played to the Ss once each at five minute intervals throughout the sleep period. Both the percentage of immediate responses and the percentage of items recalled correctly decreased as the percentage of alpha frequencies decreased. Shortly after occipital alpha frequencies disappeared from the EEG, immediate responses and item recall also stopped. This was more evident when tested by recognition than by unaided recall. Approximately 5% of the items presented during non-alpha levels were responded to immediately, recalled later, or both. A majority of these items occurred when particular EEG patterns associated with arousal occurred; alternative explanations other than sleep-learning are offered for the few remaining items. Learning during real sleep is concluded to be impractical and probably impossible. (Author)