Still another variety of memory is psycho-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 and reproduced[reproduced]. Such a reproduction is essentially 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 salivary glands 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 under physiological conditions, such, for instance, as the introduction of the stimulating substances into the buccal cavity, reappeared in exactly the same manner under the influence of psychological conditions—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 when physiologically excited 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 found that 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 process through 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 a psycho-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 synonymous terms. 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 be conscious 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 of dissociated conditions (functional amnesia, post-hypnotic states, etc.), the names of persons, places, faces, objects, and even complex ideas may flash into the mind without any element 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 as crystal 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 our everyday 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 our vocabulary is but conscious memory without localization in the 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.