LECTURE VNEUROGRAMS
We have got as far as showing that the phenomena of memory to be intelligible require that ideas which have passed out of mind must be conserved through some sort of residuum left by the original experience. But this as a theory of memory is incomplete; the question remains,How, and in what form, manner, or way, are they conserved? In other words, What is the nature of the residuum? Is it psychical or physical?[54]As we have seen, from the fact that something outside of the personal consciousness can manifest memory of a given experience at the very same moment when the personal consciousness has amnesia for that experience, we are compelled to infer that conservation must be by a medium, psychological or physiological, capable of being excited as a specific secondary process. Now this medium must be either an undifferentiated “Psyche” or specific differentiated residua. In the former case we postulate a concept of a transcendental something beyond experienceand of which, like the soul after death, we have and can have no knowledge. To this concept of an undifferentiated Psyche we shall return presently.
If the second alternative—specific differentiated residua—be the medium by which experiences are conserved, then the residua must be either specific psychological states, i.e., the original psychological experience itself as such; or neural residua (or dispositions) such as when excited are ordinarily correlated with a conscious memory. In either case the medium would be such as to permit of the experiences manifesting themselves, while so conserved outside of the personal consciousness, as a very specific secondary process, not only reproducing the original experience as memory, but elaborating the same and exhibiting imagination, reasoning, volition, feeling, etc. Unless the doctrine of the undifferentiated Psyche be accepted it is difficult to conceive of any other mode in which conservation can be effected so as to permit of the phenomena of memory outside of consciousness.
Conservation considered as psychological residua.—It is hypothetically possible that our thoughts and other mental experiences after they have passed out of mind, out of our awareness of the moment, may continue their psychological existence as such although we are not aware of them. Such an hypothesis derives support from the fact that researches of recent years in abnormal psychology have given convincing evidence that an idea, undercertain conditions, after it has passed out of our awareness may still from time to time take on another sort of existence,one in which it still remains an idea, although our personal consciousness of the moment is not aware of it. A coconscious idea, it may be called. More than this, in absent-mindedness, in states of abstraction, in artificial conditions as typified in automatic writing, and particularly in pathological conditions (hysteria), it has been fairly demonstrated, as I think we are entitled to assert, that coconscious ideas in the form of sensations, perceptions, thoughts, even large systems of ideas, may function and pursue autonomous and contemporaneous activity outside of the various systems of ideas which make up the personal consciousness. It usually is not possible for the individual to bring such ideas within the focus of his awareness. Therefore, there necessarily results a doubling of consciousness,—two consciousnesses, one of which is the personal consciousness and the other a coconsciousness. These phenomena need to be studied by themselves. We shall consider them here only so far as they bear on the problem of conscious memory. Observation has shown that among ideas of this kind it often happens that many are memories, reproductions of ideas that once belonged to the personal consciousness. Hence, on first thought, it seems plausible that conservation might be effected by the content of any moment’s consciousness becomingcoconsciousafter the ideas have passed out of awareness. According to suchan hypothesis all the conscious experiences of our lives, that are conserved, would form a great coconscious field where they would continue their existence in specific form as ideas, and whence they could be drawn upon for use at any future time.
Various difficulties are raised by this hypothesis. In the first place, there is no evidence that coconscious ideas have a continuous existence. The technical methods of investigation which give evidence of such ideas functioning outside of the awareness of the personal consciousness do not show that at any given moment they are any more extensive than are those which fill the field of the personal consciousness. Indeed, usually, the coconscious field is of very limited extent. There remains an enormous field of conserved experiences to be accounted for. So far then as coconscious ideas can be discovered by our methods of investigation they areinadequate to account for the whole of the conservation of life’s experiences.
In the second place, these ideas come and go in the same fashion as do those which make up the content of the main personal consciousness; and many are constantly recurring to become coconscious memories. The same problem, of the nature of conservation, therefore confronts us with coconscious ideas in the determination of the mechanism of coconscious memory. To explain conservation through coconscious ideas is but a shifting of the problem. If a broader concept be maintained, namely, that this coconsciousness, which can bedemonstrated in special conditions, is but a fraction of the sum total of coconscious ideas outside of the personal awareness, we are confronted with a concept which from its philosophical nature deals with postulates beyond experience. We can neither prove nor disprove it. There is much that can be said in its support for the deeper we dive into the subconscious regions of the mind the more extensively do we come across evidences of coconscious states underlying specific phenomena. Nevertheless, the demonstration of coconscious states in any number of specific phenomena does not touch the problem of the nature of conservation. In weighing the probability of the hypothesis on theoretical grounds it would seem, as I have already said in a preceding lecture, to be hardly conceivable that ideas that had passed out of mind, the thoughts of the moment of which we are no longer aware, can be treasured, conserved as such in a sort of psychological storehouse or reservoir of consciousness, just as if they were static or material facts. Such a conception would require that every specific state of consciousness, every idea, every thought, perception, sensation and feeling, after it had passed out of mind for the moment, should enter a great sea of ideas which would be the sum total of all our past experiences. In this sum-total millions of ideas would have to be conservedin concreteform until wanted again for use by the personal consciousness of the moment. Here would be found, in what you will see at once would be a real subconsciousmind beyond the content or confines of our awareness, stored up, so to speak, ready for future use, the mass of our past mental experiences. Here you would find, perhaps, the visualized idea of a seagull soaring over the waters of your beautiful bay conserved in association with the idea of the mathematical formula, a + b = c; the one having originated in a perception of the outer world through the window of your study while you were working at a lesson in algebra which gave rise to the latter. And yet conserved as ideas, as such vast numbers of experiences would be, we should not be aware of them until they were brought by some mysterious agency into the consciousness of the moment. The great mass of the mental experiences of our lives which we have at our command, our extensive educational and other acquisitions from which we consciously borrow from time to time, as well as those which, we have seen, are conserved though they cannot be voluntarily reproduced, all these mental experiences, by the hypothesis, would still have persisting conscious existences in theiroriginal concrete psychological form.
Such an hypothesis, to my mind, is hardly thinkable, and yet this very hypothesis has been proposed, though in less concrete form perhaps, in the doctrine of the “subliminal mind,” a particular form of the theory of the subconscious mind. This doctrine, which we owe to the genius of the late W. H. H. Meyers, has more recently appeared, without full recognition of its paternity, in thewritings of a more modern school of psychology. According to this doctrine our personal consciousness, the ideas which we have at any given moment and of which we are aware, are but a small portion of the sum total of our consciousness. Of this sum-total we are aware, at any given moment, of only a fractional portion. Our personal consciousness is but sort of up-rushes from this great sum of conscious states which have been called the subliminal mind, the subliminal self, the subconscious self. These conscious up-rushes make up the personal “I,” with the sense of awareness for their content.
The facts to be explained do not require such a metaphysical hypothesis. All that is required is that our continuously occurring experiences should be conserved in aform, and by an arrangement, which will allow the concrete ideas belonging to them to reappear in consciousness whenever the conserved arrangement is again stimulated. This requirement, the theory of conservation, which is generally accepted by those who approach the problem by psycho-physiological methods, fully satisfies. Before stating this theory in specific form let me mention to you still another variety of the subliminal hypothesis, metaphysical in its nature, which appeals to some minds of a philosophical tendency.
Conservation considered as an undifferentiated psychical something or “psyche.”—It is difficult to state this hypothesis clearly and precisely for it is necessarily vague, transcending as it does human experience.It is conceived, as I understand the matter, or at least the hypothesis connotes, that ideas of the moment, after ceasing to be a part of awareness, subside and become merged in some form or other in a larger mind or consciousness of which they were momentary concrete manifestations or phases. This consciousness is conceived as a sort of unity. Ideas out of awareness still persist as consciousness in some form though not necessarily as specific ideas. According to this hypothesis, it is evident that when the ideas of the moment’s awareness subside and become merged into the larger consciousness either one of two things must happen; they must either be conserved as specific ideas, or lose their individuality as states of consciousness, and become fused in this larger consciousness as an undifferentiated psychical something. Some like to call it a “psyche,” apparently finding that by using a Greek term, or a more abstract expression, they avoid the difficulties of clear thinking.
The first alternative is equivalent to the hypothesis of conservation in the form of coconscious specific ideas which we have just discussed. The second alternative still leaves unexplained the mechanism by which differentiation again takes place in this psychical unity, how a conscious unity becomes differentiated again into and makes up the various phases (ideas) of consciousness at each moment; that is, the mechanism of memory.
But, aside from this difficulty, the hypothesis is opposed by evidence which we have already foundfor the persistence of ideas (after cessation as states of consciousness) in some concrete form capable of very specific activity and of producing very specific effects. We have seen that such ideas may under certain conditions continue to manifest the same specific functionating activity as if continuing their existence in concrete form (e. g., so-called subconscious solution of problems, physiological disturbances, etc.). This phenomenon is scarcely reconcilable with the hypothesis that ideas after passing out of awareness lose their concrete specificity and become merged into an undifferentiated psychical something.[55]
Furthermore, for a concept transcending experience to be acceptable it must be shown that it adequately explains all the known facts, is incompatible with none, and that the facts are not intelligible on any other known principle. These conditions seem to me far from having been fulfilled. Before accepting such a concept it is desirable to see if conservation cannot be brought under some principle within the domain of experience.
Conservation considered as physical residua.—Now the theory of memory which offers a satisfactory explanation of the mode in which registration, conservation,and reproduction occur postulates the conserved residua as physical in nature. Whenever we have a mental experience of any kind—a thought, or perception of the environment, or feeling—some change, some “trace,” is left in the neurons of the brain. I need not here discuss the relation between brain activity and mind activity. It is enough to remind you that, whatever view be held, it is universally accepted that every mental process is accompanied by a physical process in the brain; that, parallel with every series of thoughts, perceptions, or feelings, there goes a series of physical changes of some kind in the brain neurons. And, conversely, whenever this same series of physical changes occurs the corresponding series of mental processes, that is, of states of consciousness, arises. In other words, physical brain processes or experiences are correlated with corresponding mind processes or experiences, and vice versa.[56]This is known as the doctrine of psycho-physical parallelism. Upon this doctrine the whole of psycho-physiology and psycho-pathology rests. Mental physiology, cerebral localization, and mental diseasesexcepting on its assumption are unintelligible—indeed, the brain as the organ of the mind becomes meaningless. We need not here inquire into the nature of the parallelism, whether it is of the nature of dualism, e. g., a parallelism of two different kinds of facts, one psychical and the other physical; or whether it is a monism, i.e., a parallelism of two different aspects of one and the same fact or a parallelism of a single reality (mind) with a mode of apprehending it (matter)—mind and matter in their inner nature being held to be practically one and the same. The theory of memory is unaffected whichever view of the mind-brain relation be held.
Now, according to the psycho-physiological theory of memory, with every passing state of conscious experience, with every idea, thought, or perception, the brain process that goes along with it leaves some trace, some residue of itself, within the neurons and in the functional arrangements between them. It is an accepted principle of physiology that when a number of neurons, involved, let us say, in a coördinated sensori-motor act, are stimulated into functional activity they become so associated and the paths between them become so opened or, as it were, sensitized, that adispositionbecomes established for the whole group, or a number of different groups, to function together and reproduce the original reaction when either one or the other is afterward stimulated into activity. This “disposition” is spoken of in physiological language as a lowering of the threshold of excitability—aterm which does not explain but only describes the fact. For an explanation we must look to the nature of the physical change that is wrought in the neurons by the initial functioning. This change we may speak of as aresiduum.
Similarly a system of brain neurons, which in any experience is correlated in activity with conscious experience, becomes, so to speak, sensitized and acquires, in consequence, a “disposition” to function again as a system (lowering of thresholds?) in a like fashion; so that when one element in the system is again stimulated it reproduces the whole original brain process, and with this reproduction (according to the doctrine of psycho-physical parallelism) there is a reproduction of the original conscious experience. In other words, without binding ourselves down to absolute precision of language, it is sufficiently accurate to say that every mental experience leaves behind a residue, or a trace, of the physical brain process in the chain of brain neurons. This residue is the physicalregisterof the mental experience.This physical register may be conserved or not.If it is conserved we have the requisite condition for memory; theformin which our mental experiences are conserved. But it is not until these physical registers are stimulated and the original brain experience is reproduced that we have memory. If this occurs the reproduction of the brain experience reproduces the conscious experience, i.e., conscious memory (according to whatever theory of parallelism is maintained).Thus in all ideation, in every process of thought, the record of the conscious stream may be registered and conserved in the correlated neural process. Consequently, the neurons in retaining residua of the original process become, to a greater or less degree,organized into a functioning systemcorresponding to the system of ideas of the original mental process and capable of reproducing it. When we reproduce the original ideas in the form of memories it is because there is a reproduction of the physiological neural process.
It is important to note that just as, on the psychological side, memory always involves the awakening of a previous conscious experience by an associated idea, one that was an element in the previous system of associated sensations, perceptions, thoughts, etc., making up the experience, so, on the physiological side, we must suppose that it involves stimulation of the whole system of neurons belonging to this experience by the physiological stimulus corresponding to the conscious element or stimulus. For instance, if I see my friend A, the image is not a memory, though it is one I have had many times before and has left residua of itself capable of being reproduced as memory. But if I see his hat, and immediately previously linked pictorial images of him arise in my mind; or, if, when I see him, there arise images of his library in which I have previously seen him, these images are memory. A conscious memory is always the reproduction of an experience by an associated ideaor other element of experience (conscious or subconscious). Similarly we must infer that the neurons correlated with any past mental experience are stimulated by associated neuron processes. This is the foundation-stone of mental physiology; for upon the general principle of the correlation of mental processes with neural processes rests the whole of cerebral localization and brain physiology.
Although we assume newly arranged dynamic associations of neurons corresponding to associations of ideas, we do not know how this rearrangement is brought about, though we may conceive of it as following the physiological laws of lowering of thresholds of excitability. Nor do we know whether the modifications left as residua (by which the thresholds are lowered) are physical or chemical in their nature, though there is some reason for believing they may be chemical.
Chemical and physical theories of residua.—It is possible that, through chemical changes of some kind left in the system of neurons corresponding to an experience, the neurons may become sensitized so as to react again as a whole to a second stimulus applied to one element. In other words a hyper-susceptibility may become established. There is a physiological phenomenon, known as anaphylaxis, which may possibly prove more than analogous, in that it depends upon the production, through chemical changes, of hyper-susceptibility to a stimulus which before was inert. The phenomenon isone of sensitizing the body to certain previously innocuous substances. If, for instance, a serum from a horse be injected into a guinea pig no observable reaction follows. But, if a second dose be injected, a very pronounced reaction follows and the animal dies with striking manifestations called anaphylactic shock. This consists of spasm of the bronchioles of the lungs induced by contraction of their unstriated muscles and results in an attack of asphyxia.[57]
The mechanism of anaphylaxis is a very complicated one involving the production in the blood of chemical substances called antibodies, and is far from being thoroughly understood. One theory is that sensitization consists in the “fixing” of the cells of the tissues with these antibodies. This may or may not be correct—probably not—and I am far from wishing to imply that sensitization of the neurons, as a consequence of functioning, has anything in common with the mechanism of sensitizing the body in anaphylaxis. I merely wish to point out that sensitizing nervous tissue through chemical changes is a physiological concept quite within the bounds of possibility; and, as all functioning is probably accompanied by metabolic (chemical) changes, such metabolic changes may well persist in neurons after brain reactions produce sensitization.
If this hypothesis of sensitization should be proven it would offer an intelligible mechanism of the phenomenon of memory. If the system of neurons engaged in any conscious experience were sensitized by chemical changes it would acquire a hyper-susceptibility. The system as a whole would consequently be excited into activity by any other functioning system of neurons with which it was in anatomical association and might reproduce the originally correlated conscious experience.
Various theories based on known or theoretical chemical or physical alterations in the neurons have been proposed to account for memory on the physiological side. Robertson[58]has proposed that it is of the nature of autocatalysis. Catalysis is the property possessed by certain bodies called catalyzers of initiating or accelerating chemical reactions which would take place without the catalyzer, but more slowly. “A catalyzer is a stimulus which excites a transformation of energy. The catalyzer plays the same rôle in a chemical transformation as does the minimal exciting force which sets free the accumulation of potential energy previous to its transformation into kinetic energy. A catalyzer is the friction of the match which sets free the chemical energy of the powder magazine.”[59]
Numerous examples of catalytic actions mightbe given from chemistry. The inversion of sugar by acids, the decomposition of hydrogen peroxide by platinum black, fermentation by means of a soluble ferment or diastase, a phenomenon which may almost be called vital, are all instances. According to Leduc “the action of pepsin, of the pancreatic ferment, of zymase and other similar ferments has a great analogy with the purely physical phenomenon of catalysis.”
In auto-catalysis one of theproductsof the reaction acts as the catalyzer. Now Robertson concluded, as a result of his experiments carried out on frogs, that the processes which accompany the excitation of the cells of the neurons are of the nature of catalysis; for he found that they have as one effect the production of an acid; and he also found that acids accelerate such processes which he concludes to be probably of the nature of oxidations. “The chemical phenomena which constitute the activity of a neuron cell,” he says, “seem to us then anauto-catalytic oxidation, that is to say, an oxidation in which one of the products of the reaction acts as a catalyzer in the reaction.” It occurred to him then that the physiological correlate of memory might be explained on the principle of auto-catalysis. When, to test this hypothesis, he came to compare the results of certain psychological experiments on memory, made by two different experimenters (Ebbinghaus and Smith), with the law characteristic of auto-catalytic chemical reactions, he found that they corresponded in a surprisinglyclose way with this law. That is to say, assuming the value of the residua of memory (measured by the number of syllables learnt by heart) to be proportional to the mass of the chemical product of auto-catalysis, we should expect that the increase of the number of syllables or other experiences retained by memory following increase of repetitions would obey the law of catalytic reaction as expressed in the mathematical formula established for the reaction. Now, as a fact, he found that the number of syllables that should be so retained in memory, as calculated theoretically by the formula, corresponded in a remarkable way with the actual number determined by experiment. “The agreement was closer,” the author states, “than that which generally obtained in experiments in chemical dynamics carried outin vitro.” Robertson sums up his conclusions as follows:
“5th. We have shown that the phenomenon of which the subjective aspect is called ‘memory’ is of a nature indicating that the autocatalyzed chemical reactions form the mechanism conditioning the response of the central nervous system to stimuli.
“6th. In admitting that the extent of the trace of memory may be proportionate to the mass of a product of an autocatalyzed chemical reaction unfolding itself in the central nervous system as the result of the application of a stimulus, we have shown that the relation which one theoretically deduces between the mass of memory material andthe number of repetitions corresponds to that which has been found by experience.
“7th. On the basis of the hypothesis above mentioned we have shown that the law of Weber-Fechner admits of a rational physico-chemical interpretation, and that the result thus obtained, provided the hypothesis above mentioned be an exact representation of facts, is that the intensity of the sensation is at each instant proportionate to the mass of the product of the autocatalyzed chemical reaction above mentioned and, consequently, to the extent of the trace of memory.”
While it is easy to understand that auto-catalysis may take part in the chemical process which underlies the performance of simple volition, as inferred by Robertson,[60]and perhaps reproduction in the memory process, it is difficult to understand how such a chemical action can explain conservation. The problem is not that of acceleration of an action, but of something like the storing up of energy.
Rignano[61]has proposed an hypothesis according to which the cells of the nervous system are to be considered as so many accumulators, analogous to electric accumulators or storage batteries. “The similarities and differences which nerve currents present in comparison with electric currents warrant us in assuming in nerve currents some of the propertiesof electric currents, and in attributing at the same time to the first other properties which the electric do not possess, provided these qualities are not incompatible with the others.”
Now, according to the hypothesis, the specific nervous current set up by any stimulus forms and deposits in the nucleus of the cells (through which the current flows) asubstancewhich adds itself to the others already there without changing them and which is capable, under appropriate conditions, of being discharged and restoring the samespecificcurrent by which it was produced. Each cell thus becomes what Rignano calls anelementary nervous accumulator. He points out that “both the conception ofaccumulators of nervous energy in tension, and that ofaccumulators of a specific nervous energy constituting their specific irritability,” which the hypothesis includes, are not new but “an ordinary conception very generally employed.”... “The only new thing which the above definition includes is the hypothesis that the substance, which is thus capable of giving as a discharge a given nervous current,was produced and depositedonly by a nervous current of the same specificity, but in the inverse direction, and could have been produced and deposited only by such a current.” "In just this capacity of restoring again the same specificity of nervous current as that by which each element had been deposited one would look for the cause of the mnemonic faculty, in the widest sense, which all living matter possesses. And further the very essenceof the mnemonic faculty would consist entirely in this restitution.“
”The specific elementary accumulators(previously termed specific potential elements) are thus susceptible now of receiving a third name, namely, that ofmnemonic elements." “The preservation of memories is to be ascribed to the accumulations of substance,” while “the reawakening of these memories consists in the restitution of the same currents [by discharge of the substance] as had formerly constituted the actual sensation or impression.”
By this hypothesis Rignano explains not only memory but the inheritance of acquired characters and the whole process of specialization of cells, all of which phenomena are special instances of such elementary accumulators of organic energy being formed and discharged.
Any attempt, with our present knowledge, to postulate particular kinds of chemical or physical changes in the nervous system as the theoretical residua of physiological dispositions left by psychological experiences must necessarily be speculative. And any hypothesis can only have so much validity as may come from its capability of explaining the known facts. It is interesting, however, to note some of the directions which attempts have taken to find a solution of the problem. For the present it is best to rest content with the theory to which we have been led, step by step, in our exposition, namely, that conservation is effected by some sort of physiological residua. This theory, of course, isan old one, and has been expressed by many writers. What we want, however, is not expressions of opinion but facts supporting them. It would seem as if the facts accumulated in recent years by experimental and abnormal psychology all tended to strengthen the theory, notwithstanding an inclination in certain directions to seek a psychological interpretation of conservation.
Some minds of a certain philosophical bent will not be able to get over the difficulty of conceiving how a psychological process can be conserved by the physical residuum of a physiological process. But this is only the old difficulty involved in the problem of the relation between mind and brain of which conservation is only a special example. That a mind process and a brain process are so intimately related that either one determines the other there is no question. It is assumed in every question of psycho-physiology. The only question is the How. I may point out in passing, but without discussion, that if we adopt the doctrine of panpsychism for which I have elsewhere argued[62]—namely, that there is only one process—the mental—in one and the same individual, and that what we know as the physical process is only the mode of apprehending the mental process by another individual; if we adopt this doctrine of monism the difficulty is solved. In other words, the psychical (and consciousness) isreality, while matter (and physical process) is aphenomenon, the disguise, so to speak, under which the psychical appears when apprehended through the special senses. According to this view in their last analysis all physical facts are psychical in nature, although not psychological (for psychological means consciousness), so that physiological and psychical are one. To this point I shall return in another lecture.
Neurograms.—Whatever may be the exact nature of the theoretical alterations left in the brain by life’s experiences they have received various generic terms; more commonly “brain residua,” and “brain dispositions.” I have been in the habit of using the termneurogramsto characterize these brain records. Just as telegram, Marconigram, and phonogram precisely characterize the form in which the physical phenomena which correspond to our (verbally or scripturally expressed) thoughts, are recorded and conserved, so neurogram precisely characterizes my conception of the form in which a system of brain processes corresponding to thoughts and other mental experiences is recorded and conserved.[63]
Of course it must not be overlooked that such neurograms are pure theoretical conceptions, and have never been demonstrated by objective methods of physical research. They stand in exactly the same position as the atoms and molecules and ions and electrons of physics and chemistry, and the “antibodies” and “complements” of bacteriology. No one has seen any of these postulates of science. They are only inferred. All are theoretical concepts; but they are necessary concepts if the phenomena of physical, chemical, and bacteriological science are to be intelligible. The same may be said for brain changes if the phenomena of brain and mind are to be intelligible.
And so it happens that though our ideas pass out of mind, are forgotten for the moment, and become dormant, their physiological records still remain, as sort of vestigia, much as the records of our spoken thoughts are recorded on the moving wax cylinder of the phonograph. When the cylinder revolves again the thoughts once more are reproduced as auditory language. A better analogy would be the recording and reproducing of our thoughts by the dynamic magnetization of the iron wire in another type of the instrument. The vibration of the voice by means of a particular electrical mechanism leavesdynamic tracesin the form of corresponding magnetic changes in the passing wire, and when the magnetized wire again is passed before the reproducing diaphragm the spoken thoughts are again reproduced. So, when the ideas of any given consciousexperience become dormant, the physiological records, or dynamic rearrangements, still remain organized as physiological unconscious complexes, and, with the excitation of these physiological complexes, the corresponding psychological memories awake.
It is only as such physiological complexes that ideas that have become dormant can be regarded as still existing. If our knowledge were deep enough, if by any technical method we could determine the exact character of the modifications of the dispositions of the neurons that remain as vestiges of thought and could decipher their meaning, we could theoretically read in our brains the record of our lives, as if graphically inscribed on a tablet. As Ribot has well expressed it: “... Feelings, ideas, and intellectual actions in general are not fixed and only become a portion of memory when there are corresponding residua in the nervous system—residua consisting, as we have previously demonstrated, of nervous elements, and dynamic associations among those elements. On this condition, and this only, can there be conservation and reproduction.”[64]Dormant ideas are thus equivalent to conserved physiological complexes.We may use either term to express the fact.
The observations and experiments I have recited have led us to the conclusion that conservation of an experience is something quite specific and distinctfrom the reproduction of it. They compel us to the conclusion that we are entitled, as I pointed out at the opening of these lectures, to regard memory as aprocessand the result of at least two factors—conservation and reproduction. But as conservation is meaningless unless there is something to be conserved, we must also assumeregistration; that is, that every conserved mental experience is primarily registered somehow and somewhere. Conservation implies registration.
Such is the theory of memory as aprocess of registration, conservation, and reproduction. Thus it will be seen (according to the theory) that ideas which have passed out of mind are preserved, if at all, not as ideas, but as physical alterations or records in the brain neurons and in the functional dynamic arrangements between them.
From this you will easily understand that while, as you have seen from concrete observations, we can have conservation of experiences without memory (reproduction) we cannot have memory without conservation. Three factors are essential for memory, and memory may fail from the failure of any one of them. Unless an experience is registered in some form there will be nothing to preserve, and memory will fail because of lack of registration. If the experience has been registered, memory may fail, owing to the registration having faded out, so to speak, either with time or from some other reason; that is, nothing having been conserved, nothing can be reproduced. Finally, though an experiencehas been registered and conserved, memory may still fail, owing to failure of reproduction. The neurographic records must be made active once more, stimulated into an active process, in order that the original experience may be recalled, i.e., reproduced. Thus what we call conscious memory is the final result of a process involving the three factors, registration, conservation, and reproduction.
Physiological memory.—Memory as commonly regarded and known to psychology is aconsciousmanifestation but, plainly, if we regard it, as we have thus far, as a process, then, logically, we are entitled to regard any process which consists of the three factors, registration, conservation, and reproduction of experiences, as memory, whether the final result be the reproduction of a conscious experience, or one to which no consciousness was ever attached. In other words, theoretically it is quite possible that acquired physiological body-experiences may be reproduced by exactly the same process as conscious experiences, and their reproduction would be entitled to be regarded as memory quite as much as if the experience were one of consciousness. In principle it is evident that it is entirely immaterial whether that which is reproduced is a conscious or an unconscious experience so long as the mechanism of the process is the same.
Now, as a matter of fact, there are a large number of acquired physiological body-actions which, though unconscious, must be regarded quite as muchas manifestations of memory as is the conscious repetition of the alphabet, or any other conscious acquisition. Having been acquired they areipso factoreproductions of organized experiences. We all know very well that movements acquired volitionally, and perhaps laboriously, are, after constant repetition, reproduced with precision without conscious guidance.
They are said to be automatic; even the guiding afferent impressions do not enter the content of consciousness. The maintaining of the body in one position, sitting or standing, though requiring a complicated correlation of a large number of muscles, is carried out without conscious volition. It is the same with walking and running. Still more complicated movements are similarly performed in knitting, typewriting and playing the piano, shaving, buttoning a coat, etc. We do not even know the elementary movements involved in the action, and must become aware of them by observation. The neurons remember, i.e., conserve and reproduce the process acquired by previous conscious experiences. But though it is memory it is not conscious memory, it is unconscious memory, i.e., a physiological memory. The acquired dispositions repeat themselves—what is called habit. Precision in games of skill largely depend upon this principle. A tennis player must learn the “stroke” to play the game well. This means that the muscles must be coordinated to a delicate adjustment which, once learned, must be unconsciously remembered andused, without consciously adjusting the muscles each time the ball is hit. Indeed some organic memories are so tenacious that a player once having learned the stroke finds great difficulty even by effort of will in unlearning it and making his muscles play a different style of stroke. Likewise one who has learned to use his arms in sparring by one method finds difficulty in learning to spar by another method. In fact almost any acquired movement is compounded of elementary movements which by repetition were linked and finely adjusted to produce the resultant movement, and finally conserved as anunconscious physiological arrangement. As one writer has said, the neuron organization “faithfully preserves the records of processes often performed.”
In what has just been said the fact has not been overlooked that the initiation or modification of any of the movements which have been classed as physiological memory (knitting, typewriting, games of skill, etc.), even after their acquisition, is necessarily voluntary and therefore, so far, a conscious memory, but the nice coördination of afferent and efferent impulses for the adjustment of the muscles involved becomes, by repetition, an unconscious mechanism, and is performed outside the province of the will as an act ofunconscious memory. By repeated experience the neurons become functionally organized in such a way as to acquire and conserve a functional “disposition” to reproduce the movements originally initiated by volition.
Physiological memory has indeed, as it seems, been recently experimentally demonstrated by Rothmann, who educated a dog from which the hemispheres had been removed to perform certain tricks; e. g., to jump over a hurdle.[65]
Still another variety of memory ispsycho-physiological. This type is characterized by a combination of psychological and physiological elements and is important, as we shall see later, because of the conspicuous part which such memories play in pathological conditions. Certain bodily reactions which are purely physiological, such as vaso-motor, cardiac, respiratory, intestinal, digestive, etc., disturbances, become, as the result of certain experiences, linked with one or another psychical element (sensations, perceptions, thoughts), and, this linking becoming conserved as a “disposition,” the physiological reaction is reproduced whenever the psychical element is introduced into consciousness. Thus, for example, the perception or thought of a certain person may become, as the result of a given social episode, so linked with blushing or cardiac palpitation that whenever the former is thrust into consciousness, no matter how changed the conditions may be from those of the original episode, the physiological reaction of the blood vessels or heart is reproduced. Here the original psycho-physiological experience—the association of an idea (or psychical element) with the physiological process is conserved andreproducedreproduced. Such a reproduction isessentially a psycho-physiological memory depending wholly upon the acquired disposition of the neurons.[66]
Thus, to take an actual example from real life, a certain person during a series of years was expecting to hear bad news because of the illness of a member of the family and consequently was always startled, and her “heart always jumped into her throat,” whenever the telephone rang. Finally the news came. That anxiety is long past, but now when the telephone rings, although she is not expecting bad news and no thought of the original experience consciously arises in her mind, her “heart always gives a leap and sometimes she bursts into a perspiration.”
A beautiful illustration of this type of memory is to be found in the results of the extremely important experiments, for psychology as well as physiology, of Pawlow and his co-workers in the reflex stimulation of saliva in dogs. These experiments show the possibility of linking a physiological process to a psychological process by education, and through the conservation of the association reproducing the physiological process as an act of unconscious memory. (The experiments, of course, were undertaken for an entirely different purpose, namely, that of studying the digestive processes only.) It should be explained that it was shown that the salivaryglands are selective in their reaction to stimuli in that they do not respond at all to some (pebbles, snow), but respond to others with a thin watery fluid containing mere traces of mucin or a slimy mucin-holding fluid, according as to whether the stimulating substance is one which the dog rejects, and which therefore must be washed out or diluted (sands, acids, bitter and caustic substances), or is an eatable substance and must as a food bolus be lubricated for the facilitation of its descent. Dryness of the food, too, largely determined the quantity of the saliva.
Now the experiments of the St. Petersburg laboratory brought out another fact which is of particular interest for us and which is thus described by Pawlow. “In the course of our experiments it appeared that all the phenomena of adaptation which we saw in the salivary glands underphysiologicalconditions, such, for instance, as the introduction of the stimulating substances into the buccal cavity, reappeared in exactly the same manner under the influence ofpsychologicalconditions—that is to say, when we merely drew the animal’s attention to the substances in question. Thus, when we pretended to throw pebbles into the dog’s mouth, or to cast in sand, or to pour in something disagreeable, or, finally, when we offered it this or that kind of food, a secretion either immediately appeared or it did not appear, in accordance with the properties of the substance which we had previously seen to regulate the quantity and nature of the juice whenphysiologicallyexcited to flow. If we pretended to throw in sand a watery saliva escaped from the mucous glands; if food, a slimy saliva. And if the food was dry—for example, dry bread—a large quantity of saliva flowed out even when it excited no special interest on the part of the dog. When, on the other hand, a moist food was presented—for example, flesh—much less saliva appeared than in the previous case however eagerly the dog may have desired the food. This latter effect is particularly obvious in the case of the parotid gland.”[67]
It is obvious that in these experiments, when the experimenter pretended to throw various substances into the dog’s mouth, the action was effective in producing the flow of saliva of specific qualities because, through repeated experiences, the pictorial images (or ideas) of the substance had become associated with the specific physiological salivary reaction, and this association had been conserved as a neurogram. Consequently the neurographic residue when stimulated each time by the pretended action of the experimenter reproduced reflexly the specific physiological reaction and, so far as the process was one of registration, conservation, and reproduction, it was an act of psycho-physiological memory.
That this is the correct interpretation of the educational mechanism is made still more evident by other results that were obtained; for it was foundthat the effective psychical stimulus may be part of wider experiences or a complex of ideas; everything that has been in any way psychologically associated with an object which physiologically excites the saliva reflex may also produce it; the plate which customarily contains the food, the furniture upon which it stands; the person who brings it; even the sound of the voice and the sound of the steps of this person.[68]
Indeed, it was found that any sensory stimulus could be educated into one that would induce the flow of saliva, if the stimulus had been previously associated with food which normally excited the flow. “Any ocular stimulus, any desired sound, any odor that might be selected, and the stimulation of any part of the skin, either by mechanical means or by the application of heat or cold, have in our hands never failed to stimulate the salivary glands, although they were all of them at one time supposed to be inefficient for such a purpose. This was accomplished by applying these stimuli simultaneously with the action of the salivary glands, this action having been evolved by the giving of certain kinds of food or by forcing certain substances into the dog’s mouth.”[69]It is obvious that reflex excitation thus having been accomplished by the education of the nerve centers to a previously indifferent stimulus the reproduction of the processthrough this stimulus is, in principle, an act of physiological memory.[70]
The experiences of the dogs embraced quite large systems of ideas and sensory stimuli which included the environment of persons and their actions, the furniture, plates, and other objects; and various ocular, auditory, and other sensory stimuli applied arbitrarily to the dogs. All these experiences had been welded into an associative system and conserved as neurograms. Consequently it was only necessary to stimulate again any element in the neurogram to reproduce the whole process, including the specific salivary reaction.
We shall see later that these experiments acquire additional interest from the fact that in them is to be found the fundamental principle of what under other conditions can be recognized as apsycho-neurosis—an abnormal or perverted association and memory. The effects produced by this association of stimuli may be regarded as the germ of the habit psychosis, and in these experiments we have experimental demonstration of the mechanism of these psychoses—but this is another story which we will take up by and by.
Recollection.—This is as good a place as any other to call attention to a certain special form of memory. Recollection and memory are not synonymousterms. We are accustomed to think of memory as including, in addition to other qualities, recollection, i.e., what is called localization of the experience in time and space. It connotes an awareness of the content of the memory having been once upon a time a previous experience which is more or less accurately located in a given past time (yesterday, or a year ago, or twenty years ago), and in certain local relations of space (when we were at school, or riding in a railway car with so and so). But, as Ribot points out, this (relatively to physiological memories) is ... “only a certain kind of memory which we call perfect.” For we have just seen that, when memory is considered as a process, reproduced physiological processes, which contain no elements of consciousness and therefore of localization, may be memory. But more than this, I would insist,recollection is only a more perfect kind of conscious memory. Ribot would make recollection a peculiarity of all conscious memory, but this is plainly an oversight. As we saw in previous lectures there may beconscious memories which do not contain any element of recollection, or, in other words, such conscious memories resemble in every way, in principle, the reproduction of organic neuron processes in that they have no conscious localization in the past. In dissociated personalities, for instance, and in other types ofdissociated conditions(functional amnesia, post-hypnotic states, etc.), the names of persons, places, faces, objects, and even complex ideas may flash into the mind without anyelement of recollection. The person may have no idea whence they come, but by experiment it is easy to demonstrate that they are automatic memories of past experiences.[71]In the sensory automatisms known ascrystal visions, pictures which accurately reproduce, symbolically, past experiences of which the subject has no recollection may vividly arise in the mind. Such pictures are real conscious symbolic memories.Dreams, too, as we have seen, may be unrecognized memories in that they may reproduce conscious experiences, something heard or seen perhaps, but which has been completely forgotten even when awake. Again, modern methods of investigation show that numerous ideas that occur in the course of oureveryday thoughts—names, for instance—are excerpts from, or vestiges of, previous conscious experiences of which we have no recollection, that is to say, they are memories, reproductions of formerly experienced ideas. In the absence of recollection they seem to belong only to the present. Memories which hold an intermediate place between these automatic memories and those of true recollection are certain memories, like the alphabet or a verse or phrase once learned by heart which we are able at best to localize only dimly in the past. Indeed, the greater part of ourvocabularyis but conscious memory without localization inthe past. So we see that recollection is not an essential even for conscious memories. It is only a particular phase of memory just as are automatic conscious memories.