The Principles of Psychology, Vols. 1-2

toftenuards determine transition and action, its content could not be conceived as one of the mind's permanent meanings : that is all I mean by saying that its intellectual value lies in after-memory. As a rule sensations outlast for some little time the ob jective stimulus which occasioned them. This phenomenon is the ground of those ' after-images ' which are familiar in the physiology of the sense-organs. If we open our eyes instantaneously upon a scene, and then shroud them in complete darkness, it will be as if we saw the scene in ghostly light through the dark screen. We can read off details in it which were unnoticed whilst the eyes were open.*

In every sphere of sense, an intermittent stimulus, often enough repeated, produces a continuous sensation. This is because the after-image of the impression just gone by blends with the new impression coming in. The effects of stimuli may thus be superposed upon each other many stages deep, the total result in consciousness being an in crease in the feeling's intensity, and in all probability, as we saw in the last chapter, an elementary sense of the lapse of time (see p. 635).

coexisting with the multitude of other sensations which are juxtaposed In consciousness alongside of this one persistent emotion which fs felt always in the present tense. A long time is needed ere we can attain to forgetting it, ere we can make it enter into the past. Hcei'et lateri letalis arundo. " (Ibid 583.) * This is the primary positive after-image. According to Helmholtz, one third of a second is the most favorable length of exposure to the light for producing it. Longer exposure, complicated by subsequent admission of light to the eye, results in the ordinary negative and complementary after-images, with their changes, which may (if the original impression was brilliant and the fixation long) last for many minutes. Fechner gives the name of memory-after-images (Psychophysik, n 492) to the instan taneous positive effects, and distinguishes them from ordinary after-images by the following characters : 1) Their originals must have been attended to, only such parts of a compound original as have been attended to ap pearing. This is not the case in common visual after images. 2) The strain of attention towards them is inward, as in ordinary remembering, not outward, as in observing a common after-image. 3) A short fixation cf the original is better for the memory-after-image, a long one for the ordinary after-image. 4) The colors of the memory-after-image are never complementary of those of the original.

" Impressions to which we are inattentive leave so brief an image in the memory that it is usually overlooked. When deeply absorbed, we j do not hear the clock strike. But our attention may awake after' the striking has ceased, and we may then count off the strokes. Such ex amples are often found in daily life. We can also prove the existence of this primary memory-image, as it may be called, in another person, even when his attention is completely absorbed elsewhere. Ask some one, e.g., to count the lines of a printed page as fast as he can, and whilst this is going on walk a few steps about the room. Then, when the person has done counting, ask him where you stood. He will always reply quite definitely that you have walked. Analogous experi ments may be made with vision. This primary memory-image is, whether attention have been turned to the impression or not, an ex tremely lively one, but is subjectively quite distinct from every sort of after-image or hallucination. ... It vanishes, if not caught by atten tion, in the course of a few seconds. Even when the original impression is attended to, the liveliness of its image in memory fades fast." *

The physical condition in the nerve-tissue of this pri- 1 mary memory is called by Eichet ' elementary memory.' f I / much prefer to reserve the word memory for the conscious phenomenon. What happens in the nerve-tissue is but an example of that plasticity or of semi-inertness, yielding to change, but not yielding instantly or wholly, and never quite recovering the original form, which, in Chapter V, we saw to be the groundwork of habit. Elementary habit would be the better name for what Professor Kichet means. Well, the first manifestation of elementary habit is the slow dying away of an impressed movement on the neural matter, and its first effect in consciousness is this so-called elementary memory. But what elementary memory makes us aware of is the just past. The objects we feel in this directly intuited past differ from properly recollected ob jects. An object which is recollected, in the proper sense of that term, is one which has been absent from conscious ness altogether, and now revives anew. It is brought back, recalled, fished up, so to speak, from a reservoir in which, with countless other objects, it lay buried and lost from view. But an object of primary memory is not thus

brought back ; it never was lost ; its date was never cut off in consciousness from that of the immediately present moment. In fact it comes to us as belonging to the rear ward portion of the present space of time, and not to the genuine past. In the last chapter we saw that the portion of time which we directly intuit has a breadth of| several seconds, a rearward and a forward end, and may be ' * called the specious present. All stimuli whose first nervevibrations have not yet ceased seem to be conditions of our getting this feeling of the specious present. They give rise to objects which appear to the mind as events just past.*

When we have been exposed to an unusual stimulus for many minutes or hours, a nervous process is set up which \ results in the haunting of consciousness by the impression \ ' for a long time afterwards. The tactile and muscular feel ings of a day of skating or riding, after long disuse of the exercise, will come back to us all through the night. Images of the field of view of the microscope will annoy the observer for hours after an unusually long sitting at the instrument. A thread tied around the finger, an unusual constriction in the clothing, will feel as if still there, long after they have been removed. These revivals (called phe nomena of Sinnesgedachtniss by the Germans) have some thing periodical in their nature, f They show that profound - rearrangements and slow settlings into a new equilibrium / )i ?» are going on in the neural substance, and they form the transition to that more peculiar and proper phenomenon of memory, of which the rest of this chapter must treat. The

* Richet says : " The present has a certain duration, a variable duration, sometimes a rather long one, which comprehends all the time occupied by the after-reverberation [retentissement, after-image] of a sensation. For ex ample, if the reverberation of an electric shock within our nerves lasts ten minutes, for that electric shock there is a present of ten minutes. On the other hand, a feebler sensation will have a shorter present. But in every case, for a conscious sensation [1 should say for a remembered sensa tion] to occur, there must be a present of a certain duration , of a few sec onds at least." We have seen in the last chapter that it is hard to trace the ' & backward limits of this immediately intuited duration, or specious present. The figures which M. Richet supposes appear to be considerably too large.

first condition which makes a thing susceptible of recall after it has been forgotten is that the original impression of it should have been prolonged enough to give rise to a recurrent image of it, as distinguished from one of those pri mary after-images which very fleeting impressions may leave behind, and which contain in themselves no guarantee that they will ever come back after having once faded away.* iA certain length of stimulation seems demanded by the (inertia of the nerve-substance. Exposed to a shorter in fluence, its modification fails to 'set,' and it retains no effective tendency to fall again into the same form of vibra tion at which the original feeling was due. This, as I said at the outset, may be the reason why only ' substantive ' and not * transitive* states of mind are as a rule recol lected, at least as independent things. The transitive states pass by too quickly.

Memory proper, or secondary memory as it might be styled, is the knowledge of a former state of mind after it has already once dropped from consciousness ; or rather it is the knowledge of an event, or fact, of which meantime we have not been thinking, with the additional conscious ;iess that we have thought or experienced it before. * The primary after-image itself cannot be utilized if the stimulus is too brief. Mr. Cattell found (Psychologische Studien, in. p. 93 ff.) that the color of a light must fall upon the eye fora period varying from 0.00275 to 0.006 of a second, in order to be recognized for what it is. Letters of the alphabet and familiar words require from 0.00075 to 0.00175 sec. — truly an interval extremely short. Some letters, E for example, are harder than others. In 1871 Helmholtz and Baxt had ascertained that \ when an impression was immediately followed by another, the latter quenched the former and prevented it from being known to later conscious ness. The first stimulus was letters of the alphabet, the second a bright white disk. "With an interval of 0.0048 sec. between the two excita tions [I copy here the abstract in Ladd's Physiological Psychology, p. 480], the disk appeared as scarcely a trace of a weak shimmer ; with an interval of 0.0096 sec., letters appeared in the shimmer— one or two which could be partially recognized when the interval increased to 0.0144 sec. When the interval was made 0.0192 sec. the objects were a little more clearly discerned ; at 0.00336 sec. four letters could be well recognized ; at 0.0433 sec., five letters ; and at 0.0528 sec. all the letters could be read." (Pfluger'a Archiv, iv. 325 ff J

The first element which such a knowledge involves would seem to be the revival in the mind of an image or copy of the original event.* And it is an assumption made by many writers f that the revival of an image is all that is needed to constitute the memory of the original occurrence. But such a revival is obviously not a memory, whatever else it may be ; it is simply a duplicate, a second event, having absolutely no connection with the first event except that it happens to resemble it. The clock strikes to-day ; it struck yesterday ; and may strike a million times ere it wears out. The rain pours through the gutter this week ; it did so last week ; and will do so in swcula sceculorum. But does the present clock-stroke become aware of the past ones, or the present stream recollect the past stream, because they repeat and resemble them ? Assuredly not. And let it not be said that this is because clock-strokes and gutters are physical and not psychical objects ; for psychical objects (sensations for example) simply recurring in successive editions will remember each other on that account no more than clockstrokes do. No memory is involved in the mere fact of re currence. The successive editions of a feeling are so many

* When the past is recalled symbolically, or conceptually only, it is true that no such copy need be there. In no sort of conceptual knowledge is it requisite that definitely resembling images be there (cf. pp. 471 ff.). But as all conceptual knowledge stands for intuitive knowledge, and termi nates therein, I abstract from this complication, and confine myself to those memories in which the past is directly imaged in the mind, or, as we say, intuitively known.

f E.g. Spencer, Psychology, i. p. 448. How do the believers in the sufficiency of the 'image' formulate the cases where we remember that something did not happen — that we did not wind our watch, did not lock the door, etc. ? It is very hard to account for these memories of omis sion. The image of winding the watch is just as present to my mind now when I remember that I did not wind it as if I remembered that I did. It must be a difference in the mode of feeling the image which leads me to such different conclusions in the two cases. When I remember that I did wind it, I feel it grown together with its associates of past date and place. When I remember that I did not, it keeps aloof ; the associates fuse with each other, but not with it. This sense of fusion, of the belonging together of things, is a most subtle relation ; the sense of non-fusion is an equally subtle one. Both relations demand most complex mental pro cesses to know them, processes quite different from that mere presence or absence of an image which does such service in the cruder books.

independent events, each snug in its own skin. Yesterday's feeling is dead and buried ; and the presence of to-day's is | no reason why it should resuscitate. A farther condition is required before the present image can be held to stand for a past original. That condition is that the fact imaged be expressly referred to the past, thought as in the past. But how can we think a thing as in the past, except by thinking of the past to gether with the thing, and of the relation of the two ? And how can we think of the past ? In the chapter on Time-per ception we have seen that our intuitive or immediate con sciousness of pastness hardly carries us more than a few seconds backward of the present instant of time. Hemoter dates are conceived, not perceived ; known symbolically by names, such as ' last week,' ' 1850 ; ' or thought of by events which happened in them, as the year in which we attended such a school, or met with such a loss. — So that if we wish to think of a particular past epoch, we must think of a name or other symbol, or else of certain concrete events, associated therewithal. Both must be thought of, to think the past epoch adequately. And to * refer ' any special fact to the past epoch is to think that fact with the names and events [which characterize its date, to think it, in short, with a lot lof contiguous associates.

But even this would not be memory. Memory requires more than mere dating of a fact in the past. It must be dated in my past. In other words, I must think that I di rectly experienced its occurrence. It must have that 'warmth and intimacy' which were so often spoken of in the chapter on the Self, as characterizing all experiences ' appropriated ' by the thinker as his own. A general feeling of the past direction in time, then, a particular date conceived as lying along that direction, and defined by its name or phenomenal contents, an event im agined as located therein, and owned as part of my ex perience,— such are the elements of every act of memory.

It follows that what we began by calling the ' image,' or ' copy/ of the fact in the mind, is really not there at all in that simple shape, as a separate 'idea.' Or at least, if it be there as a separate idea, no memory will go with it. What memory goes with is, on the contrary, a very complex rep resentation, that of the fact to be recalled plus its associates, the whole forming one ' object ' (as explained on page 275, Chapter IX), known in one integral pulse of consciousness (as set forth on pp. 276 ff.) and demanding probably a vastly more intricate brain-process than that on which any simple sensorial image depends.

Most psychologists have given a perfectly clear analysis of the phenomenon we describe. Christian Wolff, for ex ample, writes: " Suppose you have seen Mevius in the temple, but now afresh in Titus' house. I say you recognize Mevius, that is, are conscious of hav ing seen him before because, although now you perceive him with your senses along with Titus' house, your imagination produces an image of him along with one of the temple, and of the acts of your own mind reflecting on Mevius in the temple. Hence the idea of Mevius which is reproduced in sense is contained in another series of perceptions than that which formerly contained it, and this difference is the reason why we are con scious of having had it before. . . . For whilst now you see Mevius in the house of Titus, your imagination places him in the temple, and renders you conscious of the state of mind which you found in yourself when you beheld him there. By this you know that you have seen him before, that is, you recognize him. But you recognize him because his ; idea is now contained in another series of perceptions from that in which you first saw him. " *

" In my remembrance of George III., addressing the two houses of parliament, there is, first of all, the mere idea, or simple apprehension, the conception, as it is sometimes called, of the objects. There is com bined with this, to make it memory, my idea of my having seen and heard those objects. And this combination is so close that it is not in my power to separate them. I cannot have the idea of George III. : his person and attitude, the paper he held in his hand, the sound of his voice while reading from it ; without having the other idea along with it, that of my having been a witness of the scene. ... If this ex planation of the case in which we remember sensations is understood, the explanation of the case in which we remember ideas cannot occasion much of difficulty. I have a lively recollection of Polyphemus's cave, and the actions of Ulysses and the Cyclops, as described by Homer. Iu this recollection there is, first of all, the ideas, or simple conceptions ot the objects and acts ; and along with these ideas, and so closely com-

bined as not to be separable, the idea of my having formerly had those same ideas. And this idea of my having formerly had those ideas is a very complicated idea ; including the idea of myself of the present mo ment remembering, and that of myself of the past moment conceiving; and the whole series of the states of consciousness, which intervened between myself remembering, and myself conceiving." * Memory is then the feeling of belief in a peculiar com plex object ; but all the elements of this object may be known to other states of belief ; nor is there in the particular combination of them as they appear in memory anything so peculiar as to lead us to oppose the latter to other sorts of thought as something altogether sui generis, needing a special faculty to account for it. When later we come to our chapter on Belief we shall see that any represented object which is connected either mediately or immediately with our present sensations or emotional activities tends to be believed in as a reality. The sense of a pecu liar active relation in it to ourselves is what gives to an object the characteristic quality of reality, and a merely imagined past event differs from a recollected one only in the absence of this peculiar-feeling relation. The electric current, so to speak, between it and our present self does not close. But in their other determinations the rerecollected past and the imaginary past may be much the same. In other words, there is nothing unique in the object of memory, and no special faculty is needed to account for its formation. It is a synthesis of parts thought of as re lated together, perception, imagination, comparison and reasoning being analogous syntheses of parts into complex objects. The objects of any of these faculties may awaken belief or fail to awaken it ; the object of memory is only an object imagined in the past (usually very completely imagined ftiere) to which the emotion of belief adheres.

* Analysis, i. 330-1. Mill believed that the various things remembered, the self included, enter consciousness in the form of separate ideas, but so rapidly that they are 'all clustered into one.' "Ideas called up in close conjunction . . . assume, even when there is the greatest complexity, the appearance, not of many ideas, but of one " (vol. i. p. 123). This mythol ogy does not imp»ir the accuracy of his description of memory's object Such being the phenomenon of memory, or the analysis of its object, can we see how it comes to pass ? can we lay bare its causes ?

2) Its reminiscence, recollection, reproduction, or recall. Now the cause both of retention and of recollection is the law of habit in the nervous system, working as it does in the ' asso ciation of ideas.' Associationists have long explained recollection by asso ciation. James Mill gives an account of it which I am unable to improve upon, unless it might be by translating his word * idea ' into ' thing thought of,' or ' object,' as explained so often before.

" There is," he says, " a state of mind familiar to all men, in which we are said to remember. In this state it is certain we have not in the mind the idea which we are trying to have in it.* How is it, then, that we proceed in the course of our endeavor, to procure its introduction into the mind ? If we have not the idea itself, we have certain ideas connected with it. We run over those ideas, one after another, in hopes that some one of them will suggest the idea we are in quest of; and if any one of them does, it is always one so connected with it as to call it up in the way of association. I meet an old acquaintance, whose name I do not remember, and wish to recollect. I run over a number of names, in hopes that some of them may be associated with the idea of the individual. I think of all the circumstances in which I have seen him engaged ; the time when I knew him, the persons along with whom I knew him, the things he did, or the things he suffered ; and, if I chance upon any idea with which the name is associated, then imme diately I have the recollection ; if not, my pursuit of it is vain, f There is another set of cases, very familiar, but affording very important evi dence on the subject. It frequently happens that there are matters which we desire not to forget. "What is the contrivance to which we have recourse for preserving the memory — that is, for making sure that it will be called into existence, when it is our wish that it should ? All men invariably employ the same expedient. They endeavor to form

f Professor Bain adds, in a note to this passage of Mill's : " This process seems best expressed by laying down a law of Compound or Composite Association, under which a plurality of feeble links of connection may be a substitute for one powerful and self-sufficing link." an association between the idea of the thing to be remembered, and some sensation, or some idea, which they know beforehand will occur at or near the time when they wish the remembrance to be in their minds. If this association is formed, and the association or idea with which it has been formed occurs ; the sensation, or idea, calls up the remembrance; and the object of him who formed the association is attained. To use a vulgar instance : a man receives a commission from his friend, and, that he may not forget it, ties a knot in his handkerchief. How is this fact to be explained ? First of all, the idea of the commission is associated with the making of the knot. Next, the handkerchief is a thing which it is known beforehand will be frequently seen, and of course at no great distance of time from the occasion on which the memory is desired. The handkerchief being seen, the knot is seen, and this sensation re calls the idea of the commission, between which and itself the associ ation had been purposely formed." *

In short, we make search in our memory for a forgotten idea, just as we rummage our house for a lost object. In both cases we visit what seems to us the probable neighbor hood of that which we miss. "We turn over the things under which, or within which, or alongside of which, it may possibly be ; and if it lies near them, it soon comes to view. But these matters, in the case of a mental object sought, are nothing but its associates. The machinery of recall is thus the same as the machinery of association, and the machinery of association, as we know, is nothing but the elementary law of habit in the nerve-centres.

And this same law of habit is the machinery of retention also. Retention means liability to recall, and it means noth ing more than such liability. The only proof of there being retention is that recall actually takes place. The retention of an experience is, in short, but another name for the pos sibility of thinking it again, or the tendency to think it again, with its past surroundings. Whatever accidental cue may turn this tendency into an actuality, the permanent ground of the tendency itself lies in the organized neural paths by which the cue calls up the experience on the proper occa sion, together with its past associates, the sense that the self was there, the belief that it really happened, etc., etc., just as previously described. "When the recollection is of the * ready ' sort, the resuscitation takes place the instant

the occasion arises ; when it is slow, resuscitation conies after delay. But be the recall prompt or slow, the condi tion which makes it possible at all (or in other words, the ' retention ' of the experience) is neither more nor less than the brain-paths which associate the experience with the occasion and cue of the recall. When slumbering, these paths are the condition of retention ; ivhen active, they are the condi tion of recall. A simple scheme will now make the whole cause of memory plain. Let n be a past event ; o its ' setting ' (concomi tants, date, self present, warmth and intimacy, etc., etc., as already set forth) ; and m some present thought or fact which may appro priately become the occasion of its recall. Let the nerve-centres, ac tive in the thought of m, n, and o,

be represented by M, N, and O, re spectively ; then the existence of the paths M — N and N — O will be the fact indicated by the phrase ' retention of the event n in the memory,' and the excitement of the brain along these paths will be the condition of the event n's actual re call. The retention of n, it will be observed, is no mysterious storing up of an ' idea ' in an unconscious state. It is hot a fact of the mental order at all. It is a purely physical phe nomenon, a morphological feature, the presence of these " paths,' namely, in the finest recesses of the brain's tissue. The recall or recollection, on the other hand, is a psychophysical phenomenon, with both a bodily and a mental side. The bodily side is the functional excitement of the tracts and paths in question ; the mental side is the conscious vision of the past occurrence, and the belief that we ex perienced it before.

These habit-worn paths of association are a clear ren dering of what authors mean by 'predispositions,' 'vestiges,' ' traces,' etc., left in the brain by past experience. Most writers leave the nature of these vestiges vague ; few think of explicitly assimilating them to channels of association. Dr. Maudsley, for example, writes : " When an idea which we have once had is excited again, there is a reproduction of the same nervous current, with the conscious addition that it is a reproduction — it is the same idea phis the consciousness that it is the same. The question then suggests itself, What is the physical condition of this consciousness ? What is the modification of the anatomi cal substrata of fibres and cells, or of their physiological activity, which is the occasion of this plus element in the reproduced idea ? It may be supposed that the first activity did leave behind it, when it subsided, some after-effect, some modification of the nerve-element, whereby the nerve-circuit was disposed to fall again readily into the same action ; such disposition appearing in consciousness as recognition or memory. Memory is, in fact, the conscious phase of this physiological disposition when it becomes active or discharges its functions on the recurrence of the particular mental experience. To assist our conception of what may happen, let us suppose the individual nerve-elements to be en dowed with their own consciousness, and let us assume them to be, as I have supposed, modified in a certain way by the first experience ; it is hard to conceive that when they fall into the same action on another occasion they should not recognize or remember H ; for the second action is a reproduction of the first, with the addition of what it con tains from the after-effects of the first. As we have assumed the process to be conscious, this reproduction with its addition would be a memory or remembrance." *

In this passage Dr. Maudsley seems to mean by the 'nerve-element/ or * anatomical substratum of fibres and cells,' something that corresponds to the N of our diagram. And the ' modification ' he speaks of seems intended to be understood as an internal modification of this same particu lar group of elements. Now the slightest reflection will con vince anyone that there is no conceivable ground for suppos ing that with the mere re-excitation of N there should arise the ' conscious addition ' that it is a re-excitation. The two excitations are simply two excitations, their consciousnesses are two consciousnesses, they have nothing to do with each other. And a vague 'modification,' supposed to be left behind by the first excitation, helps us not a whit. For, according to all analogy, such a modification can only result in making the next excitation more smooth and rapid. This might make it less conscious, perhaps, but could not endow

it -with any reference to the past. The gutter is worn deeper by each successive shower, but not for that reason brought into contact with previous showers. Psychology (whicn Dr. Maudsley in his next sentence says " affords us not the least help in this matter") puts us on the track of an at least possible brain-explanation. As it is the setting o of the idea, when it recurs, which makes us conscious of it as past, so it can be no intrinsic modification of the ' nerve-element ' N which is the organic condition of mem ory, but something extrinsic to it altogether, namely, its con nections with those other nerve-elements which we called O — that letter standing in the scheme for the cerebral sub stratum of a great plexus of things other than the principal event remembered, dates, names, concrete surroundings, realized intervals, and what not. The ' modification ' is the formation in the plastic nerve-substance of the system of associative paths between N and O.