In connection with the use of the material two methods have been employed--the part method and the whole method. The learner may break the material up into sections, and study just one, then the next, and so on, or he may take all the material and go through with it from the beginning to the end and then back again. Experimental results show the whole method to be the better of the two. However, in actual practice, especially with school children, probably a combination of the two is still better, because of certain difficulties arising from the exclusive use of the whole method. The advantages of the whole method are that it forms the right connections and emphasizes the complete thought and therefore saves time and gives the right perspective. Its difficulties are that the material is not all of equal difficulty and therefore it is wasteful to put the same amount of time on all parts; it is discouraging to the learner, as no part may be raised above the threshold of recall at the first study period (particularly true if it is rote memory); it is difficult to use recall, if the whole method is rigidly adhered to. A combination of the two is therefore wise. The learner should be encouraged to go over the material from beginning to end, until the difficult parts become apparent, then to concentrate on these parts for a time and again go over from the beginning--using recall whenever possible.
A consideration of the time element involved in memorizing has given use to two other methods, the so-called concentrated and distributive. Given a certain amount of time to spend on a certain subject, the learner may distribute it in almost an infinite number of ways, varying not only the length of the period of practice, but also the length of time elapsing between periods. The experimental work done in connection with these methods has not resulted in agreement. No doubt there is an optimum length of period for practice and an optimum interval, but too many factors enter in to make any one statement. "The experimental results justify in a rough way the avoidance of very long practice periods and of very short intervals. They seem to show, on the other hand, that much longer practice periods than are customary in the common schools are probably entirely allowable, and that much shorter intervals are allowable than those customary between the just learning and successive 'reviews' in schools."[4] This statement leaves the terms very long and very short to be defined, but at present the experimental results are too contradictory to permit of anything more specific. However, a few suggestions do grow from these results. The practice period should be short in proportion as these factors are present: first, young or immature minds; second, mechanical mental processes as opposed to thought material; third, a learner who "warms up" quickly; the presence of fatigue; a function near its limit. Thus the length of the optimum period must vary with the age of the learner, the subject matter, the stage of proficiency in the subject, and the particular learner. The same facts must be taken into consideration in deciding on the optimum interval. One fact seems pretty well established in connection with the interval, and that is that a comparatively short period of practice with a review after a night's rest counts more than a much longer period added to the time spent the evening before.
There are certain suggestions which if carried out help the learner in his memorizing. In the first place, as the number of associates is one factor determining recall, the fact to be remembered should be presented in many ways, i.e., appealing to as many senses as possible. In carrying this out, it has been the practice of many teachers to require the material to be remembered to be acted out or written. This is all right in so far as the muscular reactions required are mechanical and take little attention. If, on the other hand, the child has to give much attention to how he is to dramatize it, or if writing in itself is as yet a partially learned process, the attention must be divided between the fact to be memorized and its expression, and hence the desired result is not accomplished. Colvin claims that "writing is not an aid to learning until the sixth or seventh grade in the schools." This same fact that an association only partly known is a hindrance rather than a help in fixing another is often violated both in teaching spelling and language. If the spelling of "two" is unknown or only partly known, it is a hindrance instead of a help to teach it at the same time "too" is being taught. Second, the learner should be allowed to find his own speed, as it varies tremendously with the individual. Third, rhythm is always an aid when it can be used, such as learning the number of days in each month in rhyme. Fourth, after a period of hard mental work a few minutes (Pillsbury thinks three to six) should elapse before definitely taking up a new line of work. This allows for the so-called "setting" of associations, due to the action of the general law of inertia, and tends to diminish the possibility of interference from the bonds called into play by the new work. Fifth, mnemonic devices of simple type are sometimes an aid. Most of these devices are of questionable value, as they themselves require more memory work than the facts they are supposed to be fixing. However, if devised by the learner, or if suggested by some one else after failure on the part of the learner to fix the material, they are permissible.
Memory has been classified in various ways, according to the time element, as immediate and permanent. Immediate memory is the one which holds for a short time, whereas permanent memory holds for a long time. People differ markedly in this respect. Some can if tested after the study period reproduce the material with a high degree of accuracy, but lose most of it in a comparatively short time. Others, if tested in the same way, reproduce less immediately, but hold what they have over a long period. Children as a whole differ from adults in having poorer immediate memories, but in holding what is fixed through years. Of course permanent memory is the more valuable of the two types for most of life, but on the other hand immediate memory has its own special value. Lawyers, physicians, politicians, ministers, lecturers, all need great power of immediate memory in their particular professions. They need to be able to hold a large amount of material for a short time, but then they may forget a great deal of it.
Memory is also classified according to the arrangement of the material as desultory, rote, and logical memory. In desultory memory the facts just "stick" because of the great retentive power of the brain, there are few connections, the material is disconnected and disjointed. Rote memory depends on a special memory for words, aided by serial connections and often rhythm. Logical is primarily a memory for meanings and depends upon arrangement and system for its power. Little children as a class have good desultory memories and poor logical memories. Rote memory is probably at its best in the pre-adolescent and early adolescent years. Logical memory is characteristic of mature, adult minds. However, some people excel in one rather than another type, and each renders its own peculiar service. A genius in any line finds a good desultory memory of immense help, despite the fact that logical memory is the one he finds most valuable. Teachers, politicians, linguists, clerks, waiters, and others need a well-developed desultory memory. Rote memory is, of course, necessary if an individual is to make a success as an actor, a singer, or a musician.
According to the rate of acquisition memory has been classified into quick and slow. One learner gets his material so much more quickly than another. Up to rather recent years the quick learner has been commiserated, for we believed, "quickly come, quickly go." Experimental results have proved this not to be true, but in fact the reverse is more true, i.e., "quickly come, slowly go." The one who learns quickly, provided he really learns it, retains it just as long and on the average longer than the one who learns much more slowly. The danger, from a practical point of view, is that the quick learner, because of his ability, gets careless and learns the material only well enough to reproduce at the time, whereas the slow learner, because of his lack of ability, raises his efficiency to a higher level and therefore retains. If the quick learner had spent five minutes more on the material, he would have raised his work to the same level as that of the slow one and yet have finished in perhaps half the time.
All through the discussion of kinds of memory the term "memory" should have been used in the plural, for after all we possess "memories" and not a single faculty memory which may be quick, or desultory, or permanent. The actual condition of affairs is much more complex, for although it has been the individual who has been designated as quick or logical, it would be much more accurate to designate the particular memory. The same person may have a splendid desultory memory for gossip and yet in science be of the logical type. In learning French vocabularies he may have only a good immediate memory, whereas his memory for faces may be most lasting. His ability to learn facts in history may class him as a quick learner, whereas his slowness in learning music may be proverbial. The degree to which quickness of learning or permanence of memory in one line is correlated with that same ability in others has not yet been ascertained. That there is some correlation is probable, but at present the safest way is to think in terms of special memories and special acquisitions. Some experimental work has been done to discover the order in which special memories develop in children. The results, however, are not in agreement and the experiments themselves are unsatisfactory. That there is some more or less definite order of development, paralleling to a certain extent the growth of instincts, is probable, but nothing more definite is known than observation teaches. For instance, every observer of children knows that memory for objects develops before memory for words; that memory for gestures preceded memory for words; that memory for oral language preceded memory for written language; that memory for concrete objects preceded memory for abstractions. Further knowledge of the development of special memories should be accompanied by knowledge as to how far this development is dependent on training and to what extent lack of memory involves lack of understanding before it can be of much practical value to the teacher.
Just as repetition or exercise tends to fix a fact in memory, so disuse of a connection results in the fact fading from memory. "Forgetting" is a matter of everyday experience for every one. The rate of forgetting has been the subject of experimental work. Ebbinghaus's investigation is the historical one. The results from this particular series of experiments are as follows: During the first hour after study over half of what was learned had been forgotten; at the end of the first day two thirds, and at the end of a month about four fifths. These results have been accepted as capable of rather general application until within the last few years. Recent experiments in learning poetry, translation of French into English, practice in addition and multiplication, learning to toss balls and to typewrite, and others, make clear that there is no general curve of forgetting. The rate of forgetting is more rapid soon after the practice period than later, but the total amount forgotten and the rate of deterioration depend upon the particular function tested. No one function can serve as a sample for others. No one curve of forgetting exists for different functions at the same stage of advancement or for the same function at different stages of advancement in the same individual, much less for different functions, at different stages of advancement, in different individuals. Much more experimental work is needed before definite general results can be stated.
This experimental work, however, is suggestive along several lines, (1) It seems possible that habits of skill, involving direct sensori-motor bonds, are more permanent than memories involving connections between association bonds. In other words, that physical habits are more lasting than memories of intellectual facts. (2) Overlearning seems a necessary correlate of permanence of connection. That is, what seems to be overlearning at beginning stages is really only raising the material to the necessary level above the threshold for retention. How far overlearning is necessary and when it becomes wasteful are yet to be determined. (3) Deterioration is hastened by competing connections. If during the time a particular function is lying idle other bonds of connection are being formed into some parts or elements of it, the rate of forgetting of the function in question is hastened and the possibility of recall made more problematic. The less the interference, the greater will be the permanence of the particular bonds.
A belief maintained by some psychologists is in direct opposition to this general law that disuse causes deterioration. It is usually stated something like this, that periods of incubation are necessary in acquiring skill, or that letting a function lie fallow results in greater skill at the end of that period, or briefly one learns to skate in summer and swim in winter. To some extent this is true, but as stated it is misleading. The general law of the effect of disuse on a memory is true, but under some circumstances its effect is mitigated by the presence of other factors whose presence has been unnoted. Sometimes this improvement without practice is explained by the fact that at the last practice period the actual improvement was masked by fatigue or boredom, so that disuse involving rest and the disappearance of fatigue and boredom produces apparent gain, when in reality it but allows the real improvement to become evident. Sometimes a particular practice period was accompanied by certain undesirable elements such as worry, excitement, misunderstandings, and so on, and therefore the improvement hindered or masked, whereas at the next period under different conditions there would be less interference and therefore added gain. All experimental evidence is against the opinion that mere disuse in and of itself produces gain. In fact, all results point to the fact that disuse brings deterioration.