An Introduction to Comparative Psychology
Chapter 6: Memory
C. Lloyd Morgan
IN likening consciousness in its constant onward progress to a wave, we have noted that, besides the impression, idea which occupies its summit or crest, it comprises so, at any moment, certain rising or waxing elements, and certain falling, fading, or waning elements. The waxing period is of variable length, and is difficult to estimate. When a stimulus is received on the nerve-ends of any sense-organ there elapses a certain time before clear consciousness results. Some of this time is occupied in the transmission of the impulse along the afferent nerve. This altogether outside consciousness,-a purely physiological matter. But when the conscious centre is thrown into activity, there is a shorter or longer space of time occupied the development of the impression in consciousness, or we may presumably express it from the physiological point of view, by the rising of the cerebral disturbance to dominance. Impressions or ideas which are simple and familiar develop rapidly; when I they are complex and unfamiliar they develop more slowly. Even if we have a fair reading acquaintance with a foreign language, we find that it takes longer to read a page of that language than a page of our own. The somewhat unfamiliar words suggest ideas less readily than those of our native tongue. There is also a wide range of individual variation in the rate of development of ideas. Some people are naturally slow; hers naturally quick, It does not necessarily follow that those in whom ideas develop slowly are inferior in mental
(100) worth to those in whom ideas develop rapidly. Sharp quick boys and girls do not always make original and exact thinkers. We may say then that the rate of development of the impression or idea, -remembering that these terms are applied to that which forms the crest of the psychical wave, or that which is in the focus of consciousness, depends (1) upon the mental constitution of the individual, (2) upon the familiarity of the impression or idea, and (3) upon its complexity.
The fading or waning of impressions or ideas along the, hinder slope of the psychical wave is a familiar fact, and one of great importance. Impressions or ideas do not cease instantly, but fade gradually. The meteor that shoots across the sky leaves a subjective track of light, due to the gradual fading of the earlier impressions. The continuity of all our impressions and ideas is of like order to the continuity of the meteor track. If the elements of consciousness were absolutely instantaneous in their occurrence and their cessation, the whole character of our mental life would be different from that of which we have practical experience. It has already been shown that the force of any word in a, sentence is largely determined by what has preceded it. But if the occurrence and cessation of each idea were instantaneous, the preceding idea could in nowise influence the succeeding ideas. Or take the case of mental arithmetic. We could not follow out even a simple series of calculations if the result of one process were not carried forward to form the basis of the next. Suppose we say, for example : Take 12 ; add 15 ; divide by 3 ; answer 9. The idea of 27 as the result of the first addition must be still present to consciousness when the idea of dividing by 3 is suggested. It is this overlap which is one factor in giving continuity to such a process, and to consciousness and thought in general.
The rate of fading of different impressions and ideas is
(101) probably very different. The fading is rapid for some sense-stimuli. Suppose that a series of similar sound-stimuli I upon the car:. It is clear that they cannot be distinguished as separate unless the effect of the first has faded in the sense before the next comes. When the sense-fading (as we may term this fading of the results of simple stimuli) is nil, we cannot perceive any interval between them, -- i. e., they fuse into a continuous sound. But Von Helmholtz has shown that we can distinguish 132 musical beats " in a second ; and Professor Exner distinguished two successive snaps of an electric spark when the interval between them was only 1/500th of a second. With the eye the sense-fading is very much slower. If sparks follow each other with an I interval of less than 1/25th of a second they appear to be continuous. In the case of touch impressions the results of observation are somewhat discrepant; but it is probable that when more rapid than from 25 to 35 in a second they are felt as continuous.
In these cases the sense -impression in consciousness is of the simplest possible nature, corresponding, we may suppose, to a brain-disturbance restricted in area and of little complexity. Exact measurements of the rate of fading of ore complex impressions and ideas are at present impracticable We are thrown back on introspection and retrospection, and on general considerations., When we read a paragraph or write one, or are speaking, we are more or less distinctly conscious as we read, write, or titter one word of much that has gone before. If a. speaker to whom we are listening begins a sentence in one construction and ends it in another, the former has not faded from consciousness, and we ate aware of the discrepancy. When the sentences are long, and overburdened with subsidiary clauses and parentheses, we not infrequently find that the beginning has faded before the end is reached. This is more markedly the case with sentences as heard than as read. In reading,
(102) a rapid glance of the eye back on the track it has been following serves to revive the fading ideas. But in listening to a speech or a lecture this is impossible. Hence in a lecture or speech construction quite admissible in the essay sounds laboured and awkward. Hence, too, in speaking to and writing for children and comparatively uneducated people the sentences should be short, and the construction direct and simple.
Ideas which are strongly touched with emotion are those which fade most slowly. A stupid or unintentional breach of good manners or social etiquette -a thing better left, unsaid-will hover in the background of one's consciousness, and haunt one unmercifully for a whole evening.- The news of a great sorrow abides in the mind, and tinges all our thought with sadness. The accepted lover sees everything through rose-tinted glasses.
We may say, then, that in this matter of fading, the impressions which result from simple and oft-experienced stimuli fade rapidly; that complex impressions and ideas fade more slowly ; and that ideas which are strongly tinged with emotion linger longest in consciousness. And we may fairly suppose that the physiological conditions on which this psychical fading depends, are to be sought in the continued duration of the cerebral disturbances which accompany them.
It is clear that in any sequence of impressions and ideas the rates of fading of the several ideas will be different, or, to express the same fact in other words, their duration as marginal elements in consciousness will be different. In reading a paragraph, it is only the salient ideas that are carried on as marginal constituents of the psychical wave ; the subsidiary ideas, and minor detail-., drop Out in order of their lack of importance. And this differential fading, as we may term it, thus allows of the condensation of the net result of a long series of ideas in the final state of consciousness in which the series culminates.
The fading of impressions or ideas is sometimes spoken of as " primary memory." It is better, however, to restrict the word memory to the reinstatement or revival, through secondary suggestion, of psychical elements or constituents which have faded from consciousness. Thus the sight of violets has for me a tendency to call to mind, in memory, a particular spot in a quaint old garden, often visited in childhood; that is to say, violets have for me a tendency, through association of ideas, to form the focal starting-point of a purely representative visual scene.
Now in what respects does this purely representative visual scene differ from the presentative visual scene in which the violet before me is now set? In the first place, it lacks that vividness and insistency which characterizes direct presentation, and which is due to immediate excitation through nerve channels.' But this is by no means all. Those who have exceptionally strong visualizing power can make a representative focal image more vivid and insistent than the presentative scene on which they are vacantly gazing. For most of us, however, our representative images lack vividness, lack detail, lack body, and, if I may so say, do not bear close and minute examination. One cannot focus first one object and then another in a scene representatively imaged, -- or at least I cannot do so. Closely connected with this point is a second difference between representation and presentation, namely, that the former carries with it a certain foreignness to the subconscious and marginal presentations of the moment, I look up from my page, for example, and have a -clear idea (image) of the bunch of bananas I saw on the table this morning at lunch. It carries with it a margin of the dessert dish on which the fruit lay, and other more or less dim surroundings. And all this. is quite foreign to the subconscious presentations of the moment, -- my manuscript, my study table,' the dog on the hearth-rug, and so forth. This
(104) foreignness or incongruity supports the lack of vividness and insistency in differentiating the representative image in memory from the presentative impression. And the more vivid and particular the idea,-- that is, the nearer it -approaches in these respects an impression,-- the more vivid are the revived and marginal surroundings of that image, and hence the greater the foreignness to the presentative margin. In dreams, and in certain abnormal waking states, the presentative margin of normal experience is absent or suppressed; and then the distinction between the representative and presentative tends to disappear, and the images assume the semblance of reality. A third point in which the representative differs from the presentative is its evanescence. Images, as they are normally experienced, lack for most of us that permanence which presentations owe to the continuity of the impulses received through the afferent nerves. The representative image, under normal conditions, only for a short time occupies the focus to the exclusion of the presentative visual impressions. Finally, there is what we may term the rational background, which enables us to differentiate the representative, however vivid, from the presentative. We know all the while, in the margin of our consciousness, that the image, however definite, is an image. We are here dealing, it must be remembered, with normal sane experience. In abnormal or insane experience the rational background may be absent, or the foreignness to presentative states may be unfelt, or the evanescence may give place to permanency, and representative images and ideas may come to dominate the mind with all the insistency of presentative realities, it must, moreover, be, particularly noticed that the re-instatement rarely or never reproduces a previous state of consciousness. It may contain a more or less faithful reproduction of a previous state of consciousness, but this reproduction only forms part of the new state of conscious-
(105) -ness. And this is a further reason why a representation, by secondary suggestion, no matter how vivid and insistant, is seldom or never, under normal conditions, mistaken for a direct presentation by primary suggestion. It only forms part of the present state of consciousness. Let represent a state of consciousness of which A is the focal element, b c the margin or body of the wave. Let this be vividly remembered at a subsequent time. The wave will then be represented thus, d e being the new margin or setting at that subsequent time. It is clear that these two states of consciousness and are different. And that the latter is not (though it does contain) a reproduction of the former.
In the case just considered, the focal element A carries with it in remembrance its original marginal setting a b. I remember, for example, with many details of marginal setting, the cobra that I saw on a granite slab surrounded with protea bushes on the basal slopes of Table Mountain. If I meet a man in the street, whose acquaintance I made some time ago at the house of a mutual friend, I am reminded of the circumstances under which we first met, of the place of our meeting, and the time. His face suggests a particular scene or particular scenes in my past life. The faces of our familiar friends of long standing, however, do not -as a rule suggest particular associations. They have been seen so often, and under so many circumstances, that the particular associations have become evanescent, and given place to divergent associations. So too with the familiar objects and occurrences of our daily life; they have ceased to have particular associations. The formula
(106) for revival, thus becomes there being no particular setting of A reinstated; and this, not because A was ever experienced without a setting, but because it has been experienced in so many settings that there is no revival off any particular one of them.
It is clear that there are two prerequisites of reinstatement, -first, the previous occurrence of the impression, idea, or marginal element to be reinstated; and secondly, the retention of something whereby the subsequent reinstatement is rendered possible. The former requires no comment here. With regard to the latter, the retention, we have already seen that we cannot in strictness say that ideas or elements of consciousness are retained in and by the mind. We must fall back on brain-physiology for an explanation of the so-called retention of impressions or ideas. The ideas as such have ceased to exist ; but the brain-structure has been modified in such a way that under appropriate conditions similar ideas will be again produced. An analogy will make this clearer. When we speak into a phonograph the tones of our voice are not hidden away in, and retained by, the cylinder of the instrument - but the wax or other material is indented, as a result of the incidence of the sound-waves, in such a way that it is capable of reproducing similar sound-waves at a subsequent time. So, too, the brain tissue is so modified by the nervous disturbances which are the accompaniments of an impression that, under appropriate neural conditions, they tend to reproduce similar nervous disturbances which are accompanied in consciousness by a reinstatement of the impressions in the form of an idea, It is in this sense only that we may speak of the retention of ideas.
According to some students of physiological psychology there are separate parts or cells, the so-called " memory-cells," whose special function it is to perform the office of retention. When an impression A is produced in correlation
(107) with certain molecular disturbances, an effect a is produced elsewhere in the brain. Reinstatement is on this view a reproduction of this collateral effect a. This hypothesis is, in my opinion, unsatisfactory, and without warranty in observed fact. It introduces an unproved and unnecessary complication in the nervous mechanism. It is more probable that the occurrence of the disturbance associated with A leaves a tendency to the indirect or secondary reproduction of a similar disturbance A, and that the impression and its reinstatement involve one and the same area of disturbance. Be this as it may, how the tendency is established, and how it is retained, is a problem with which we must' leave physiology to deal, being content, psychologically, to accept the fact of such establishment and retention. Psychology does, however, tell us somewhat concerning retention. We find, for example, that individuals vary a good deal in their retentiveness. Macaulay had only to read over a list of wranglers, and he could reproduce the list long afterwards without effort or mistake. Few of us could do this: some would remember, say, half-a-dozen of the names which perhaps struck us as familiar or peculiar; others would remember one or two - many would remember none of the names. Retentiveness is, in fact, to a large extent a psycho-physiological datum ; something given in the brain-structure and mental character of each individual; something which we can no more alter than we can alter the size of our heads, or to take what is perhaps a closer analogy the size of our muscles. By careful use and training We may develop our muscles within the limits assigned to them by nature. So, too, by careful exercise we may perhaps develop our retentiveness within the limits assigned to it by nature. Opinions differ, however, as to how far mere retentiveness (that is ability to retain apart from ability to recall) can be strengthened by use; and it is a matter that is exceedingly difficult to test.
In the same individual retentiveness varies somewhat with the state of the nervous system. Impressions evoked when we are fagged out and weary, are not so readily retained as those evoked when we are fresh and vigorous. The impressions and ideas of the morning and in the springtime of life, are more readily retained than those of the evening and in life's autumn or winter. Old people often remember vividly the impressions and ideas of their youth; what they fail to retain is the recent impressions and ideas. Their brains reproduce what is already registered therein; but fail to effect new registrations.
Other things being equal, the more vivid the impression, the more interest it arouses and the more we attend to it the greater the probability of its being retained. An impression may be strengthened by keeping it for some time in the focus of consciousness which involves attending to it, by bringing it into focus through different sense channels, -as where we make a child look carefully at, pronounce audibly, and write down a name we wish him to remember; and by repetition. The impression is apt to fade in a shorter or longer time. Occasional revival of the impression or idea at progressively increasing intervals leads to its more and more perfect retention. These modes of imprinting ideas on the mind, or establishing particular modifications of brain-structure, are well recognised by teachers.
Ability to retain and ability to recall are generally regarded as two different psychological faculties ; but they are closely connected. The recall or reinstatement is, indeed, the only evidence we have of retention. We can know nothing about ideas that are retained but are beyond recall. Close as the connection undoubtedly is, however, it is advisable to distinguish between retention and reinstatement.
First, we may notice the distinction between casual or desultory memory and systematic memory. Let us contrast the two. The possessor of a good desultory memory has
(109) no difficulty in learning to spell, easily commits to memory strings of dates or lists of grammatical examples or exceptions; remembers without effort the Latin, Greek, French, or German equivalents of our English words. Foreign languages are readily acquired, since the vocabulary thus presents little difficulty. Such an one remembers the addresses of all his acquaintances, and the birthdays of all his relations and friends. His mind is stored with a mass of miscellaneous information, which seems always. within easy call, and ready for the purposes of illustration. He is generally a good talker, a delightful raconteur, a superb diner-out. If he be a man of wide reading, he has always an apt quotation ready to his tongue. He remembers the plots of all the novels he has read, the exact routes taken by travellers and explorers, the winners of the Derby since be was a boy, and even the changes of political opinion of our leading statesmen.
Contrasted with such an one, is the man who remembers none of these things. He enjoys a novel, but forgets the plot in a week. He has read his Shakespeare with delight, but could scarcely quote you a single line. He fancies his friend has left London, but whether for Newcastle, Ramsgate, or Penzance, lie cannot say. He knows that be heard that piece of music exquisitely played somewhere, and at sometime, and was told who composed it, but whether it is by Offenbach or Wagner he forgets. He has yearly to be reminded of his wife's birthday. But get him to speak of philology, or botany, or the history of philosophic thought, as the case may be, and he will astonish you with the vast stores of his learning, and the methodical sequence of his ideas. He forgets no fact which bears upon his special subject, and which can find a definite place in its system of ideas. Such is an extreme case of systematic memory.
There can be no doubt that a good desultory memory gives a man great advantages over his fellows. It is generally
(110) associated with wide and general interests ; and is due partly to strong natural retentiveness, and partly to the rapid and firm establishment of association by contiguity, and by similarity (resemblance), in so far as such similarity is tolerably obvious and near the surface of things. For there is a tendency in minds of this type to be superficial rather than deep, picturesque rather than logical, descriptive rather than analytical, reproductive rather than original. The analytical thinker, as he listens to the genial conversation of such men, admires perhaps their rapid flow of ideas, their fund of anecdote, their descriptive power. But he is apt to ask himself what after all there is in all this that is worth remembering.
When a man's memory is chiefly of the systematic type, matters are remembered in and through their significance, their value as evidence, their bearing upon some hypothesis, in virtue, that is to say, of their perceived relationships. Associations by contiguity, or by superficial and casual resemblance, are neither strong nor enduring. It is those deeper associations of a rational or logical character, which we have termed associations by perceived similarity of relations, which alone have permanence. The two kinds of memory are not, however, by any means of necessity mutually exclusive. The wide generality of the one, and the narrow specialism of the other, are often combined, and must be so combined to form a really great and commanding intellect.
It is questionable, as we have already hinted, whether desultory memory, dependent upon association by'. contiguity and by superficial resemblance, is susceptible to any appreciable extent of improvement by training and exercise. But systematic memory which is, in the main, dependent upon logical or rational association through the perception of relationships is more open to improvement in this way. Even here, however, it is rather the establishment of a definite system and skill in its use that is capable
(111) of improvement, than what we may term native power of remembering. It is power of recollecting rather than power of remembering which we can cultivate. To remember is an involuntary process beyond control ; while to recollect is a voluntary process requiring some effort. Systematic arrangement and logical association of ideas help us to recollect. And when habit has rendered recollection along certain systematic lines comparatively easy, such recollection becomes closely akin to natural remembrance, just as in other cases to be hereafter considered, the results of habit approach closely to the results of instinct. From this point of view desultory memory is for the most part an inborn faculty ; systematic memory is to some extent an acquired habit.
In clear remembrance and recollection there are often definite associations of place and time. Place associations we need not here consider. But since memory deals with the reinstatement of past impressions as present ideas, it will be well briefly to discuss the question of time-localization. The cobra incident that I spoke of a few pages back has for me not only place associations, but time associations. It occurred during the latter part of my five years residence at the Cape. By an effort of recollection I can fix the time more exactly as the spring of 1882. Applying the term " time-localization " to the process of. assigning to an occurrence its position in the remembered duration of my life, let us proceed to consider how such localization in time is effected.
The first point to notice is, that only in the present moment of consciousness are events spread out before us in what may be termed their real time-size or duration. When, in the moment of recall, past events are represented in consciousness they are foreshortened or telescoped. When I run over in retrospect the events of my last summer holidays, or of my visit to the Auvergne, occurrences separated
(112) by days or weeks pass before my mind's eye in a few minutes. If this were not so it would take us an hour to recall the events of any past hour of our lives. The foreshortening or telescoping is effected through missing out or forgetting all the minor details, and recalling only the salient points. And this faculty of forgetting details it is which makes retrospection as we know it possible. The telescoping is more and more marked the further we look back into the past. The events of this morning body forth in memory with considerable fulness of detail. The events of this day last week have already been merged in the blended perspective of the past. Of last year only certain salient points stand forth; and further back still the rapid, glance of memory only discloses some of the more important,' milestones which mark the progress of life's journey.
Localization in time-as, for example, when we endeavour to recollect when such and such an occurrence took place is the determining of the position of the occurrence with reference to the salient landmarks of our past experience. I received a telegram yesterday, and I wish to recall when it reached me. It was after my morning lecture, and before I had my lunch. That sufficiently localizes it. When did I first meet So-and-so? It was after I returned from the Cape and before I was appointed lecturer in Bristol. By focussing attention on this period I can localize more exactly. I had heard of the Bristol post, but had not yet been appointed.
Such, I take it, is the manner in which we habitually proceed when we wish to recollect when an event took place, or to localize it in time. It involves the taking in at a glance of the chief landmarks of our life's history ; the reference of the occurrence to a position between two of these landmarks ; the focussing of the attention on this intervening period and the further defining of the time-position of the event with reference to the minor landmarks
(113) thus brought to mind. But how are the main landmarks themselves localized in time? By reference to the other landmarks leading from our earliest.' remembrances and recollections to the immediate past and so to the present moment of consciousness. In this present moment of consciousness our primary experience of sequence and duration is gained. Our past life, which we can review in memory, is an extension backwards through retrospective thought of experience gained in the present moment of consciousness. Our anticipations of the future are a similar extension forwards of this ex-perience. Anticipation is prospective representation.
I have so far said nothing about the aid afforded by dates in assisting us to remember when an event took place. Dates are indeed secondary aids -- most convenient and helpful, but none the less secondary-to time-localization. They are also common reference-points, enabling us to compare our own landmarks with those of other people, and thus to form a time-scale that is not only individual but social. My reader knows nothing of the landmarks of my life; I know nothing of the landmarks of his life. life. But if I say that I returned from the Cape in 1883, he can at once localize the occurrence in time by reference to some event in his own life with which this date is associated. Thus the date is a common reference-point by means of which I may compare my own time-localization with those of any one else. It is social and not merely individual.
Of some of the salient events of my life's story I know the dates ; of my going to school, my leaving school, my visit to America, my engagement, my marriage, and so forth. For other dates I have to calculate from these fixed points. Had I a tenacious desultory memory no doubt I should remember a larger number of such dates than I do. But I think that the generality of people are pretty much in my position in this matter.
So far f have been considering the past of which I have direct and individual experience. But far back beyond my own individual remembrances and recollection stretches the greater past of history with all its social importance and value. Of this I have no direct first-hand experience ; I have only the indirect second-hand experience gained from books and oral teaching. Into this greater past, so as to cover symbolically its longer periods, I extend that conception of time which has been found serviceable in dealing with the short space of my individual life. just as I can review, foreshortened in memory, the historical events that have I taken place in my own lifetime, so I can review the events that took place in the eighteenth century, the times of Elizabeth, or the reign of William the Conqueror. And just as dates are convenient, and socially indispensable, for marking the salient points of the history of the last twenty years, so are dates of equal value for marking the salient points of the centuries gone by.
It must be remembered, however, that dates are symbolic. Symbolic of what ? Of localization in time. It is only as an aid to correct time-localization that dates are of any value. The mere repetition of a date tacked on to an event through association by contiguity is almost valueless educationally if it convey no conception of the relation --of the event to other events in time-sequence. I ask a boy when Jonson's " Every Man in his Humour " was published. He answers glibly 1596. 1 say: Was Shakespeare still living? He looks confused; and I continue: Was Cromwell dead? to his still greater confusion. And yet lie can give me pat the dates of Shakespeare's death and of Cromwell's protectorate. He has been badly taught-parrot fashion. He has the materials for time-localization, but the, conception has not dawned upon him, or been explained to him Another boy, of whom the same question concerning Jonson's comedy is asked, replies: "I do not know the
(115) exact date. But it was after the publication of the ' Faerie Queen,' and before Bacon's 'Essays' appeared. It must have been between 1590 and 1597." That boy intelligently localizes in time.
From simple reinstatement through association by contiguity, to the accurate localization in time of an event which took place long ago, is a far cry. This does but illustrate the fact, however, that revival or reinstatement is a necessary condition of a wide range of mental operations. And here it will be well to draw a distinction, one which we shall find to be of the utmost value and importance, between memory as merely reinstating, and memory in its reflective and retrospective aspect as affording the material of thought and knowledge. The difference between the ,two is this, that memory as merely reinstating does no more 'than introduce into the psychical wave revivals of former constituents of the wave of consciousness ; while memory as reflective and retrospective carries with it some reference to the relations of that which is revived -- some reference to the how, the where, and the when. The sight of a man's face in the street may vividly recall through reinstatement a scene, perhaps at a dinner-table, in which he formed a focal object, and perchance some witty remark of his. But if I then recollect where I met him, when, and under what circumstances, there is something more than reinstatement. I look back, reflectively, and view the occurrence in its relations to other events. The introduction of the relations is the introduction of a new factor. Of these relations that which involves the conception of time has been illustrated. Localization in time is, as we have seen, viewing the event in its true time relations. It involves reflection and retrospection, or looking back on the past course of the psychical wave and assigning to the event its true position in relation to other events.
According to some psychologists, simple reinstatement
(116) through association should not be included under memory.' Thus Dr Thorndike, in his Animal Intelligence, while urging the great advantage of well-developed association processes, insists that the permanence of associations does not necessarily imply memory, properly so called. In this narrower definition, which, though much may be said in its favour, is not here adopted, there must be in all true memory a recognition ; there must be a reference, vague or exact, to past experience in which the remembered event occurred. In brief, according to this view, any remembrance or recollection, as distinguished from mere reinstatement, is dimly or clearly recognized as mine. The localization of occurrences in space and time, or the definite assignment of a fact to its place in our system of knowledge, is the outcome of the development of the recognition process through the rendering focal of the spacial, temporal, or logical relationships involved.
It should be observed that the statement made on p. 106 with regard to physiological retention cannot be accepted as sufficient by philosophy or metaphysics, And apart from some system of metaphysics memory is inexplicable. On the metaphysical hypothesis sketched in the Prolegomena, the brain-tissue is only the phenomenal aspect of an underlying reality wherein alone is to be found (or assumed) that continuity of which memory is the familiar conscious aspect.