Learn While You Sleep
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What makes us remember? Why do some people have good memories and others poor? Why do we remember some things with ease and find it almost impossible to retain others?

Is there a technique of remembering, a trick of association, a gimmick of arrangement? Or is it as simple a matter as remembering what we want to remember, and forgetting what we don't want to remember?

In defining memory, James D. Weinland writes that there is no sharp dividing line between learning and memory, since all learning is based on memory. He makes time the one distinction, in that memory is learning that persists.

A memory so ingrained that it requires no effort at all is a habit. Memory is a function of the mind, and greater intelligence and better memory usually occur together.

Memorizing, according to Knight Dunlap, has to do with thinking about as well as of the item. It also has to do with desire to learn, and with persistence. He recommends avoiding constant evaluation of progress; progress should be checked, but infrequently.

Full attention should be paid to the subject, and, added to that, he suggests negative practice—the effort to forget. The reason for negative practice is the theory that effort is detrimental to achievement.

So often we are not able to remember something no matter how hard we try, then when we stop trying we suddenly find ourselves remembering. So Dunlap turns it around and says to try to forget, and this effort will get in the way of forgetting.

In the remembering of details, Dunlap says, the purposes behind the remembering must be considered. Is the subject memorizing in order to use the details thus acquired or for the sake of a stunt? Dunlap is weighing values as well as means in this discussion. He also mentions the importance of personal and social adjustment.

The over-all theory behind Dunlap's discussion is that the way of learning lies in the formation of habits. Here we see a similarity to the conditioning theory.

But in Dunlap's approach other factors are stressed as equally important. In order to break habits, for instance, it is necessary to understand the situation, to accept the proper ideals, to have a genuine desire to realize these ideals, and to persist in practice aimed at accomplishing the end in view.

There are habits of thought and habits of emotional response. Learning ability, which he calls intelligence, varies, with home influence, social training, basic learning ability and incentive.

Ian M. L. Hunter, in discussing memory, tells us it is easier to recognize than to recall. Among the considerations in determining how quickly we can memorize are meaningfulness, which helps, and the amount of material to be memorized, for as the material increases, the length of time necessary for learning increases disproportionately.

The characteristics of the learner must be considered as well—his emotional state, the deterrent effects of illness, fatigue, drugs, or excitement. It is theorized that age affects learning capacities as well. It is claimed that there is a progressively diminishing increase in memory span with the increase of age.

Intelligence brings with it high learning efficiency. And speed has values apart from the time-saving aspects: it has been found that a fast learner learns better.

Hunter reports that reading plus recitation results in better learning and remembering than reading alone. The explanation is that the combination of the two involves active participation, provides knowledge of results and increases motivation, and constitutes direct preparation for later recalling.

He finds pros and cons in the argument about whole versus part learning. Both, he concludes, have their uses. Whole learning is good for short pieces, but a combination would be necessary for longer and more difficult material.

• Short learning sessions are advised.

• The best results are achieved when they are spaced.

• Accurate first impressions are extremely important.

• Rhythm in the material is important.

• Overlearning (review) is recommended, as well as integrating the material.

There is no one cause of forgetting, Hunter states. The reason could be physiological—for instance, a deterioration of the trace, that is, of the organic changes produced by learning; or an actual injury or disease of the brain. Another cause could lie in behavioral processes, which include retroactive interference, altered conditions during remembering, and repression.

It is pointed out that interpretation can affect or distort memory. This accounts for inaccurate witnessing, where the facts reported are the results of observation plus interpretation.

This includes on-the-spot interpretation, which happens almost without the observer's awareness, and the subtle changes that occur in the course of thinking about the event later. The memory becomes clouded and colored by myriad influences.

Hunter says the hypnagogic state (Reverie Period) just between waking and sleeping, is the time the subject is particularly rich in imagery, which is frequent and vivid.

An interesting point is made about the difference between memory and the use of knowledge. It has been noted that along with the development of skill in abstract thinking there is a decrease in imaging ability.

If there is a correlation between imaging ability, as there appears to be, and receptivity in general, are we then, to assume that analytical thinking tends to inhibit the capacity for quick rote memorizing?

This leads on to the phenomenon known as photographic memory. Hunter tells us it is an incorrect term, that this kind of memory isn't really photographic. It is actually a form of visual imaging, very strong in children, but rare among adults.

This capacity is known among the researchers as eidetic memory—a high degree of visual imaging, but not totally photographic in that everything that is seen is registered, no matter how irrelevant to the material. Selectivity is involved—something unknown to the camera lens.

Hunter draws a fine line between learning and memory. Little or nothing is known of the physiological process. He lists as efficient techniques of study: selective observing or perceiving, organizing of the material and distributing the effort involved in study, and he rates organizing and finding the underlying principle most effective. Efficient learning, he says, is deliberate and fully conscious—not drill.

The neat little packages of advice offered by memory specialists are the conclusions drawn from the numerous investigations made in the field. Careful experiments have been conducted and the results tabulated and correlated, and from these results certain behavior is concluded to be representative of the process.

Since the tests usually involve only a sample group, they cannot be considered absolute proof, but they do indicate a tendency, at the very least. Here is a brief review of some of these investigations.

One of the earliest memory experiments was conducted by Hermann Ebbinghaus at Harvard during 1892-93. He came to the conclusion that things heard and seen spontaneously were remembered best.

Subsequent experiments did not always bear this out. In some instances variations were found among age groups. Some found hearing more effective, some sight.

In 1912 Henmon noted that most individuals are of the mixed imagery type. But again in subsequent experiments different results were obtained. Wewick tested seventy college subjects in 1932, and found that the auditory mode of learning was superior for them, both for immediate recall and for recall after a delay of from five days to five months.

In 1934 Stanton's experiments bore out this finding, but not with statistical significance in all cases. In the area of suggestibility, or influencing, Wilke found the audiovisual combination more effective, and since his subjects did not know they were being tested this experiment was more like an actual life situation.

Frank R. Elliot notes that prior to 1932 simple or nonsense materials were used, and in these experiments the results favored the visual over the auditory mode of learning.

But since 1932, when larger numbers have been tested, using connected, sense materials, auditory was favored over visual learning. Elliot conducted tests for recall and recognition, using fictitious advertisements. His results showed the highest scores in a combined visual-auditory approach, the next highest for auditory methods, and the third for visual.

In discussing why the best results were obtained when audio and visual stimuli were combined, Elliot states that tests have shown that a summation of stimuli, facilitation, and heightening effects are characteristic of the simultaneous stimulation of two receptor systems.

He notes that we hear better when we see as well, and that we see better with a combination of other sense stimuli—auditory, olfactory, and cutaneous. This phenomenon is accounted for by the spread of energy in the cerebrum, flowing in two—or perhaps all—directions. It was found that under combined audio-visual stimuli accuracy improved as well.

The visual-auditory approach seems, Elliot finds, to reduce distractions, improve attentions, remove uncertainty, enhance accuracy, and reinforce memory impression.

In its own area, the sound of the human voice has been shown to be of great value. There is social satisfaction involved. Cantrill and Airport found that people prefer, two to one, to hear news on the radio rather than to read it in a paper and nine-to-one to hear a speech rather than read it.

Elliot notes, however, that the role of habit must be considered in this argument of audio vs. visual, for people adapt to shifts.

Elliot found that memory was better after broken or serial presentation. The advantage, he concluded, seems to lie in the distribution of learning and in repetition. Another of his conclusions is that education shows in the difference in memory. College groups usually remember more than non-college groups.

The explanation offered is that they see more relations and their associational capacities are stronger. Tests to determine the differences in memory capacities between the sexes were inconclusive. In some areas men were shown to remember more than women, but the combined visual-auditory advantage was not so significant for men.

The possibilities that women listened to the radio more, or were less well educated, were offered as explanations. The impact of television since these tests were conducted may reveal different results.

Elliot suggests that perhaps the reason for the advantage of audio over visual stimuli lies in the fact that during audio experiences no time is spent examining.

The stimulus is received as presented, so there is a more equal distribution of attention.

Early in the century a study of auditory memory consciousness was made by F. Kuhlmann. He used phonograph records to investigate recall of auditory material.

As he saw it there were three modes of recall: auditory imagery of the words appeared at once without any process preceding it as an aid to recall; concrete visual imagery of the persons and things referred to appeared first as a means of recalling the words; or words were inferred from the contents as already recalled.

Kuhlmann found that the character of auditory imagery varied with reference to the completeness with which the sentence was recalled directly (in auditory terms material is remembered not in sentences but in fragments); that it varied with reference to the degree in which the words were imaged in the quality of the individual voice; that the imagery of the voice in its true character sometimes appeared without the recall of any words.

Kuhlmann also found changes in recall according to the lapse of time between hearing the material and testing for recall, which he did after one, three and six weeks. The greatest changes occurred between the immediate and the second recall.

There was a striking transformation from the immediate to the last recall, in both the manner of recall and the final result, in the auditory imagery of the words.

Visual imagery was not constant in immediate recall; it preceded the auditory in most cases in the last recall, and increased in amount, so that the visual imagery alone presented the whole scene and event. The general clearness and vivacity of the visual imagery remained about constant throughout the several recalls.

The total amount recalled in auditory terms decreased markedly, sometimes leaving only a sentence or two that could be recalled after six weeks' interval. The fragmentary character of the recall, however, did not increase much.

There were progressive stages in the quality of auditory imagery: first, the voice was imaged in its individual quality; next it was imaged merely as a bass or tenor; after that it appeared in a somewhat characterless fashion; and finally there was no definite or complete auditory imagery at all before the words were formulated and stated in the recall.

The processes involved in memorizing also changed. At first, attention was divided between actual sounds and visual imagery. The first repetition or two brought with them the process of naming sounds and imitating them.

During further repetitions visual imagery and naming quickly disappeared, and motor processes of imitation increased for a while, but tended, finally, to drop out.

Kuhlmann had his subjects recall sounds in a semi-passive way, without making any effort in the direction of detail or vividness. In 53% visual imagery appeared first, in 15% naming the subject of recall came first, and in 8% motor processes came first. Visual imagery preceded auditory imagery in 55%, the name preceded the auditory image in 24% and motor processes preceded auditory imagery in 13%.

Visual imagery was described as consisting of the things that produced the sounds (although attention to visual imagery for purposes of recalling details proved detrimental to recall); of the things going through the motions they would make in producing the sounds; or of visual sound analogues, consisting of arbitrary forms, sometimes including colors, whose characteristics were patterned after the characteristics of the sounds.

The motor processes which were used in imitating the sounds were inseparably connected with the effort to recall the sound vividly and minutely.

The auditory imagery was very fragmentary, and could not usually be directly controlled voluntarily, but only through motor processes, or, in some instances, through visual imagery.

Sleep-learning observers have pointed out that some time periods are more favorable to learning and some less. Edward Van Ormer conducted an investigation to determine the best time for study in terms of how well we remember later what we have learned.

He examined retention after intervals of sleep and waking and found that on the whole recall was most efficient after sleep. Other investigators he reported on came to the same general conclusion; Jenkins and Dallenback said that "forgetting is not so much a matter of the decay of old impressions and associations as it is a matter of interference, inhibition, or obliteration of the old by the new." Heine said improved memory resulting from "sleeping on" the learned material was due to the elimination of the retroactive inhibition produced by the day activities which normally follow learning.

Van Ormer goes along with this. He explains that sleeping after studying gives best results because of the absence of the inhibition or obliteration of the learned material by the waking activity.

He theorizes that another factor enters into it, that it is possible that the waking activity not only inhibits and obliterates what has been learned, but that it also prevents or holds in check a preservation or consolidation process which continues for a while in the nervous system after the impression of the learned material.

This preservation or consolidation process may often be at its highest point for the first part of the hour following learning. He suggests that it is also possible that the process of waking and the activity that takes place before there is any relearning is inhibitory as well. Still, he points out, results show there is a preservative process.

Van Ormer offers the explanation that perhaps recall is benefited by the refreshing effect of sleep on the organism, but notes that the same results were achieved whether the subject slept one hour or eight hours. Moreover, the results were the same one hour after the study period regardless of whether the hour was spent sleeping or waking.

The results suggested, on the whole, that a primary factor in forgetting is the action of the interpolated activity, because it inhibits a consolidation or preservation process and produces inhibition and obliteration of learned material.

Retention was, for the most part, better after four or eight hours of sleep than after the same time interval of waking.

Little is forgotten during sleep. This appears to be an argument in favor of late night study, and perhaps also in favor of "cramming" before examinations.

A. E. Wagner conducted one of the early experiments "to determine the number of repetitions necessary to memorize and retain with maximum certainty a miscellaneous collection of facts."

He noted the effectiveness of Jesuit methods of thorough and repeated drill and was thus inspired to study the value of frequent repetition. He concluded that it was best to employ a relatively small number of repetitions with a constantly increasing interval of time between the repetitions, continuing over a rather long time period.

His results showed that high school students, on the average, needed six repetitions (of his selected miscellaneous facts), and grade school students averaged about seven repetitions.

The physiological explanation of memory generally accepted today is that everything we experience or learn produces some physical change in the brain, leaves some kind of a trace, sometimes called an engram¹ .

Weinland suggests that the memory trace may be a lowering of the resistance to passage of the nervous impulse from one cell to another, so that the next impulse passes across more easily.

We have already discussed Thorndike's laws of learning, which state the importance of motivation, repetition, reward and meaningfulness; and the Gestalt emphasis on the whole, the meaningful configuration (Weinland points out a danger of inaccuracy with regard to detail in the Gestalt principle).

Weinland does not agree with the memory improvement authorities that anyone can be trained to have a good memory. Improvement is certainly possible, but the one invariable is the person's potential.

This cannot be increased. He tells us that psychologists agree with William James that retentiveness, that is, capacity for remembering, cannot be improved by effort or training, because it is dependent on the brain structure. Within the limits of the potential, however, memory can be improved like any other skill.

Among the common and useful memory devices that many people employ without outside instruction are numbering, classifying, and visualizing.

Those who have not learned to use these devices by themselves can gain in efficiency by applying themselves in this way. Motivation is important too—not just in the sense of wanting to improve one's memory—but in the more particular sense of wanting to learn specific things for specific purposes.

The more driving the need or desire, the more effective will be the memory.

Interest is important, and explains the fact that memories, even remarkable memories—are usually especially good in only one area. People with amazing memories for things in general are probably interested in everything. Weinland concludes that a person's memory can be called poor only if he forgets many things that deeply interest him after making an effort to remember them.

Sometimes forgetting is simply a matter of incomplete learning due to lack of attention or interest. An impression has never really been made on the mind. Weinland and others think there may be evidence that nothing experienced is ever completely forgotten, unless there is a brain injury or atrophy.

The explanation that forgetting is the result of fading of the trace is contradicted by the recovery of many forgotten memories in the course of psychotherapy, by association, and also in hypnotherapy, where patients have been 'regressed' and, under hypnosis, even speak and write like a child of the age desired, with emotions and experiences to match, unchanged by what happened later in the subject's life.

It has also been found that recall of meaningful materials is as much as 50% better under hypnosis. Recall is also better in other states characterized by relaxation —abstraction, free association, "twilight sleep," and simple relaxation.

Brain injuries sometimes result in loss of memory, but not always. Often there is no noticeable amnesia, or it is temporary.

The location in the brain of the injury (or of surgery) makes a difference in the effect on memory. Certain diseases may result in amnesia, for instance, syphilis, epilepsy and Korsakoff's disease (a result of alcoholism).

Serious lack of oxygen or blockage of blood circulation through the brain can have permanent destructive effects on the brain and therefore on aspects of memory.

Deterioration of memory with the years may be part physiological, and part psychological, Weinland says. It is physiological when an old person forgets things he wants to remember, but it is psychological when he forgets things which have become unimportant to him.

Both factors contribute to the apparent fine memory for events of childhood and youth and poor memory for recent events.

Weinland tells us that, according to the evidence, brain damage is greater in its effect on memory of recent events, and in addition the present and future are frequently of less importance to old people who may find more satisfaction in remembering earlier happiness.

Loss of interest in life makes them dismiss memories of no importance, and then the ever present tendency to forget what we don't care about remembering takes over. But generalizations cannot be made; some old people remain mentally alert and suffer no serious memory loss, and they make up for such as there is by experience, accumulation of knowledge, ability to organize, and increased capacity to comprehend.

Weinland goes on to state that some forgetting is active, or defensive—selective, in order to clear the mind of material irrelevant to the immediate purpose. He reminds us that Pavlov found that associations can be unlearned.

Freud said we bar unpleasant things from consciousness, and sometimes complicate the forgetting—and betray ourselves—with what are known now as Freudian slips.

He found that childhood experiences which had lasting and damaging effects but were apparently forgotten, had merely been repressed because they were too disturbing to be admitted, and that these incidents could be recalled with sufficient effort and encouragement.

Weinland reports that the theory that we forget unpleasant things has been tested, and that the findings indicate that usually pleasant things are remembered better than unpleasant things, but there is no great difference quantitatively.

Further, both pleasant and unpleasant things are remembered better than indifferent things, and pessimists tend to remember unpleasant things and forget pleasant ones.

Repression, then, exists in one way or another. Amnesia is a complete escape through repression; this frequently proves to be disturbing and thus a motivation is created for recovery.

Small-scale amnesia, or "blacking out," is often protective. Repression can also operate for reasons of pride, to avoid anxiety, and to make past memories more acceptable by alteration of the facts.

Memories fade more rapidly when they are not in use, or reviewed. (Here Weinland makes a distinction between recall and recognition; the former is lost much more quickly than the latter.)

But the material learned is not altogether lost, for it can be relearned in less time than was necessary when the material was completely new.

In the course of his experimentation, Ebbinghaus found that forgetting begins rapidly and then slows down. Davis and Moore tested retention and found that material meaningful to the learner was remembered better.

Nadorah Smith reported that with material retained for a long time the forgetting process is slowed down considerably. E. J. Smith found retention high in motor acts; he explained this as due to the fact that greater organization is required for this sort of learning, and Weinland adds that since motor learning is often overlearning, retention is further aided.

The interference of emotional factors (e.g., love, fear, anger, insecurity) can cause forgetting, as can another manifestation of complete concentration—absent-mindedness.

Forgetting can sometimes be attributed to blocking of the item for which recall is desired.

And finally, when a task is completed, it is frequently forgotten because the mind has decided there is no further need to remember anything about it.

Proceeding from investigation of the nature of remembering and forgetting, various authorities have attempted to devise principles, rules, and systems to aid in improvement of memory.

Somewhere around 500 B.C. Simonides worked out a system of assigning things to be remembered, a position in space; a method also employed by Quintilian and Cicero. In the seventeenth century Henry Hudson applied a similar system involving association by visual symbol.

A complicated digit-letter system was used as far back as the fifteenth century, appeared in Germany in the seventeenth century, and in England in the nineteenth century; this approach involves considerable practice and is applicable only to rote learning. It is also useful for theatrical type stunts.

Successive-comparism systems—broad associations in a kind of chain systems—have been invented; these often require remembering as much inventive associational material as can be found in the already logically associated material of a well-planned text.

Another system was based on paired associates, like pen and ink, and combined number associations with visual imagery of absurd combinations which were presumed to make the combination, and thus the key word, memorable.

Known as the Roth Memory Course, its major value is in the field of entertainment and for particular occasions, not for lengthy retention.

Weinland's principles behind memory improvement stress the importance of interest, of selection, of complete attention, of accuracy in the first learning against speed, of proper instruction if necessary, of understanding (meaningful learning), of background associations to reinforce the meaning and discrimination to discern relatedness, of the "mental set" or intention to remember — effective even for a specific length of time, of confidence that we can remember, of a reasonable degree of ego involvement, of specific meaningful associations or connections, of a background of knowledge, of good organization and classification of the material (“A good memory is like a well-organized and well maintained filing system” he writes), of combining whole and part learning, of dividing material to be learned into separate groups in order to simplify the task, and of reinforcing the memory by repetition and use.

Weinland rephrases the above principles for remembering a particular fact:

• Try to see its significance, try to be interested in it, or at least in the value of remembering it.

• Give it your attention, be sure you have it right.

• Be sure you fully understand it.

• Intend to remember it.

• Be confident you can remember it.

• Involve the ego if possible.

• Associate it with other related facts.

• File it in its proper place in your memory system.

• See it as a part of a larger whole.

• If there is a basis for doing so, learn it as part of a small group of related facts.

In discussing study methods, Weinland emphasizes the importance of an environment conducive to study. He too points out the value of using all the senses to reinforce memory, and reminds us that verbalization can be an aid to motor learning.

In discussing the auditory and visual aspects, he refers to an investigation by F. C. Bartlett, who found that visual memorizers tend to be quick and confident in their learning and in reproducing the subject matter—quite directly, with less dependency on grouping, comparisms and secondary associations than auditory memorizers, who in addition reached for signs and cues and descriptions, and who are less confident in recalling subject matter.

On the other hand, visual memorizers were more likely to change the material in recall, or to change the order or add material not originally included. A combination of the two is, of course, preferable to either one method alone.

Visual aids are always useful in fixing a memory, as are efficient reading habits. Marking up a book or taking notes in a lecture also help, by further affixing attention in the course of learning and for future reference when review is necessary, as does recitation for the purpose of self-testing.

Review soon after learning, because of the quick early forgetting tendency, is useful, and spaced practice is important. Weinland tells us that sometimes the review is more meaningful if there are slight changes in method or point of view; this is of interest in our study because the sleep-learning investigations report better results when the material is not changed.

The recommendations to study before going to sleep are modified by Weinland, "unless physically or mentally overtired." He also recommends, on the basis of several studies, learning the material in the evening before going to bed, and reviewing it the next morning. He too values overlearning, but feels it should be used with discretion.

And he notes that miscellaneous items can best be remembered by finding a pattern or principle for it: a pattern in the spelling or in the arrangement of numbers, in features and appearance and behavior of people, in the rhythm and melody of music, in the customs of a group, and in suffixes in language; a principle of spelling or grammar rules, a principle behind group customs which presents them in a unified way— and so forth.

Rhyme, numbering, alphabetical order, abbreviation, a kind of acrostic system of making words out of first letters of a series of facts, pigeonholing (Simonides Spatial Arrangement), translation of numbers and letters already referred to, paired associates and chain associations (also referred to above) are all mentioned by Weinland as memory devices that have some value but also limitations.

Numbering ceases to be useful when large numbers of items are to be considered; alphabetical order may result in blocking; abbreviation can be confusing, or even come before remembering the whole fact for which the abbreviation stands; acrostics are artificial and may discourage attempts to understand the material; pigeonholing is not a good substitute for arrangement by logic and organization; number letter translation is a complication requiring special learning and practice and appears to be useful for little more than tricks; paired associates and chain association have been discussed elsewhere and are not recommended for wide use. But all of these devices can be useful and helpful in particular circumstances.

Since reports on sleep-study point to so much success in learning foreign languages it will be interesting to consider what wide-awake learners have to say on the subject. Weinland considers interest and enthusiasm of primary importance, interest not only in the language, but in the country where it is spoken.

Conversing with a person for whom this is the native tongue, and reading newspapers and magazines in the language serve both to heighten interest and practice.

Pictures and advertisements help the beginner to understand the captions in foreign literature. Knowledge of current events through reading papers in English (or the student's own language) makes it easier to understand articles on the subject in a foreign paper. Subscribing to periodicals also offers good spaced practice, which is found useful in remembering.

The card system, with the foreign word on one side and the English word on the other, is recommended, with frequent practice in self-testing. Attention and accurate first learnings, with awareness of both the similarity to and the difference from the English equivalent, are stressed.

A combination of the visual and auditory aspects of both the word and the thing it represents is necessary to make the subject think in a new language. Finding the relatedness among various foreign words is valuable, and idioms too, must be tied together. Reciting and self-testing in writing is essential, especially for the grammar.

Surveying the recommendations of the memory experts, what conditions and methods do we find conducive to recall? And how far does sleep-learning coincide with these findings?

We find consistency in many areas. There is agreement that certain time periods are better than others, that study just before sleep helps avoid retroactive inhibition of memory, also that motivation, knowledge of achievement, reinforcement by review, thinking about the material, learning during spaced intervals, understanding and repeating are vital.

Reciting and writing out the material, relaxation, interest, confidence, health and freedom from drugs, over-learning, reinforcement of motor learning with verbalization, the proper environment, and general conditioning or habit formation are also important and helpful elements of memory.

The effort to forget does not seem to be important in sleep-learning, since this form of memory stems directly from subconscious activity. If that constant evaluation of progress indicates worry, anxiety, and possible barriers in the early stages, it is implicitly considered undesirable in sleep-learning as in conscious memorizing.

Meaningful material is easier to learn both awake and asleep, according to the authorities of both schools. Association and coexistence are not stressed, except as a general free-association activity in connection with repetition, in the literature of sleep-research, nor is there too much discussion of whole and part learning, broken and serial presentation, or grouping of material.

Sleep-study advocates report no age limitations in learning capacity in older people, and seem to disagree that there are individual limits to learning potential. But they all agree that incentive is important, and the entire system of sleep-learning precludes the possibility of wandering or divided attention.

They recognize the interference of emotional problems and recommend sleep-therapy as a means of overcoming these. They seem not to be directly concerned with home influence and social training, although these are probably recognized as part of the emotional attitude. Distortion of interpretation is hardly likely during the first learning, since the subject is asleep, and the possibility of distortion occurring is subsequently not mentioned.

Accuracy of first learning seems to be assured, if the tape has been prepared correctly and accurately.

The question of whether the material is pleasant or unpleasant or indifferent and the effect on memory is not dealt with.

Reports indicate that rote-learning of just about anything is possible, but incentive and motivation and interest are recommended, so this can conceivably be related to the pleasure-displeasure theories.

Efficient techniques, selectivity and organization of material, finding underlying principles or patterns—all these are recommended by sleep-learning advocates as part of the learning process.

Consistent with psychologists' findings is that auditory learning which is the basis for sleep-learning, has been found to be more effective than visual learning.

Among the conscious aids to memory which are helpful to a degree, few appear to be important in sleep-study. Numbering, classifying, visualizing, spatial arrangement, digit number systems, paired or chain associations, abbreviations—these are not mentioned at all.

Rhyme is referred to as the easiest material to learn during sleep, and is thus recommended to begin with. Ego involvement is certainly apparent in the sleep-therapy recordings, as well as in the relaxing and preludes to sleep-learning tapes.

It would be interesting if the sleep-learners were able to conduct tests to discover whether or not memory acquired during sleep suffers in recall from proactive inhibition (previously learned material) or from blocking, and what degree of cue dependency is involved in this method.

According to testimonials, students who learned foreign languages during sleep achieved amazing results in a short time. When we compare these claims with the busy schedule recommended by authorities of conscious learning of a language, we can only gasp at the time and effort saved.

Again tests would be interesting to discover how well the student acquires the living feel of the language, understanding and accuracy in the use of grammar, and whether or not he thinks in the new language.

On the whole, there appears to be enough consistency in the theories of conscious memory and sleep-memory to indicate considerable validity in the latter approach. Certain conscious effort must still be made, if the knowledge thus acquired is to be used intelligently. But the degree to which drilling and rote learning, which are required in many areas of study, can be cut down will obviously stimulate interest and incentive to experiment with the possibility of sleep-study methods being of great use to us all.