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 leaves dynamic traces in 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 conscious experience 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 distinct from 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 a process and 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 assume registration; that is, that every conserved mental experience is primarily registered somehow and somewhere. Conservation implies registration.
Such is the theory of memory as a process 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 experience has 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 a conscious manifestation 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 much as manifestations of memory as is the conscious repetition of the alphabet, or any other conscious acquisition. Having been acquired they are ipso facto reproductions 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 and used, 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 an unconscious 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 of unconscious 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]]