In the Psychological Bulletin for July, 1955, Charles W. Simon and William H. Emmons have analyzed and evaluated the ten most important studies in the field. All these studies were concerned with memory. Does sleep-teaching help the pupil in his task of learning by rote? And to what extent is material whispered into the ear of a sleeping person remembered next morning when he wakes? Simon and Emmons answer as fol­lows : "Ten sleep-learning studies were reviewed. Many of these have been cited uncritically by commercial firms or in popular magazines and news articles as evidence in support of the feasibility of learning dur­ing sleep . A critical analysis was made of their experi­mental design, statistics, methodology and criteria of sleep. All the studies had weaknesses in one or more of these areas. The studies do not make it unequivocally clear that learning during sleep actually takes place. But some learning appears to take place in a special kind of waking state wherein the subjects do not re­member later on if they had been awake. This may be of great practical importance from the standpoint of economy in study time, but it cannot be construed as sleep learning . . . . The problem is partially con­founded by an inadequate definition of sleep."

Meanwhile the fact remains that in the American Army during the Second World War (and even, experi­mentally, during the First) daytime instruction in the Morse Code and in foreign languages was supple­mented by instruction during sleep — apparently with satisfactory results. Since the end of World War II sev­eral commercial firms in the United States and else­where have sold large numbers of pillow speakers and clock-controlled phonographs and tape recorders for the use of actors in a hurry to learn their parts, of politicians and preachers who want to give the illusion of being extemporaneously eloquent, of students pre­paring for examinations and, finally and most prof­itably, of the countless people who are dissatisfied with themselves as they are and would like to be sug­gested or autosuggested into becoming something else. Self-administered suggestion can easily be recorded on magnetic tape and listened to, over and over again, by day and during sleep. Suggestions from the outside may be bought in the form of records carrying a wide variety of helpful messages. There are on the market records for the release of tension and the induction of deep relaxation, records for promoting self-confidence (much used by salesmen), records for increasing one's charm and making one's personality more magnetic. Among the best sellers are records for the achievement of sexual harmony and records for those who wish to lose weight. ("I am cold to chocolate, insensible to the lure of potatoes, utterly unmoved by muffins.") There are records for improved health and even records for making more money. And the remarkable thing is that, according to the unsolicited testimonials sent in by grateful purchasers of these records, many people actually do make more money after listening to hypnopaedic suggestions to that effect, many obese ladies do lose weight and many couples on the verge of divorce achieve sexual harmony and live happily ever after.

In this context an article by Theodore X. Barber, "Sleep and Hypnosis," which appeared in The Journal of Clinical and Experimental Hypnosis for October, 1956, is most enlightening. Mr. Barber points out that there is a significant difference between light sleep and deep sleep. In deep sleep the electroencephalograph re­cords no alpha waves; in light sleep alpha waves make their appearance. In this respect light sleep is closer to the waking and hypnotic states (in both of which al­pha waves are present) than it is to deep sleep. A loud noise will cause a person in deep sleep to awaken. A less violent stimulus will not arouse him, but will cause the reappearance of alpha waves. Deep sleep has given place for the time being to light sleep.

A person in deep sleep is unsuggestible. But when subjects in light sleep are given suggestions, they will respond to them, Mr. Barber found, in the same way that they respond to suggestions when in the hypnotic trance.

Many of the earlier investigators of hypnotism made similar experiments. In his classical History, Practice and Theory of Hypnotism , first published in 1903, Milne Bramwell records that "many authorities claim to have changed natural sleep into hypnotic sleep. According to Wetterstrand, it is often very easy to put oneself en rapport with sleeping persons, espe­cially children. . . . Wetterstrand thinks this method of inducing hypnosis of much practical value and claims to have often used it successfully." Bramwell cites many other experienced hypnotists (including such eminent authorities as Bernheim, Moll and Forel) to the same effect. Today an experimenter would not speak of "changing natural into hypnotic sleep." All he is prepared to say is that light sleep (as opposed to deep sleep without alpha waves) is a state in which many subjects will accept suggestions as readily as they do when under hypnosis. For example, after being told, when lightly asleep, that they will wake up in a little while, feeling extremely thirsty, many subjects will duly wake up with a dry throat and a craving for water. The cortex may be too inactive to think straight; but it is alert enough to respond to suggestions and to pass them on to the autonomic nervous system.

As we have already seen, the well-known Swedish physician and experimenter, Wetterstrand, was espe­cially successful in the hypnotic treatment of sleeping children. In our own day Wetterstrand's methods are followed by a number of pediatricians, who instruct young mothers in the art of giving helpful sugges­tions to their children during the hours of light sleep. By this kind of hypnopaedia children can be cured of bed wetting and nail biting, can be prepared to go into surgery without apprehension, can be given confidence and reassurance when, for any reason, the circum­stances of their life have become distressing. I myself have seen remarkable results achieved by the therapeu­tic sleep-teaching of small children. Comparable re­sults could probably be achieved with many adults.