Dream recall as a function of method of awakening.

Eleven subjects were awakened from dream peiiods (defined in terms of Dement and Kleitman's eye-movement criteria) and asked to describe their dream experience. Subjects more often believed that they were awake and/or thinking when the awakening was gradual than when the awakening was abrupt (P < .05). Reports in which the subject believed that he had been awakened from a dreamless sleep were more frequent for the first several eye-movement periods of the night than for eye-movement periods which occurred toward morning (P < .05). Depth of sleep, as defined by the arousal threshold, also became lighter for successive eye-movement periods during the night (P< .05).