The full significance as well as the validity of this theory can be properly estimated only in the light of the facts which have been revealed by modern technical methods of investigation. After all, it is the consequences of a theory which count, and this will be seen to be true particularly as respects memory. The pragmatic point of view of counting the consequences, of determining the difference that the theory makes in the understanding of the mental processes of normal and abnormal life, reveals the importance to us of validating the theory. The consequences of the psycho-physiological theory are so far-reaching, in view of its bearing upon a large number of problems in normal and abnormal psychology, that it is worthy of sustained and exhaustive examination. I will, therefore, briefly résumé the various classes of facts which support the theory and which any adequate theory of memory must satisfactorily explain. For, as will appear, besides the common facts of memory pertaining to everyday life, there are a large number of other facts which can be observed only when the mind is dissected, so to speak, by pathological processes, and by the production of artificial conditions, and when investigations are carried out by special technic. Irrespective of any theory of explanation, a knowledge of these facts is extremely important for an understanding of many phenomena in the domain of both normal and abnormal psychology.
The meaning of conservation.—We all know, as an everyday experience of mankind, that at one time we can recall what happened to us at some particular moment in the past, and at another time we cannot. We know that when we have forgotten some experience if we stimulate or refresh our memory, as the lawyers say to us on the witness-stand, by reference to our notes, appropriately called memoranda, the original experience may come back to mind. Often at one moment we cannot recall a verse, or a name, or a piece of acquired knowledge, while at another time, a little later, we can. We have a feeling, a perhaps justifiable belief, that a desired piece of knowledge is not lost, that it is back somewhere in our minds but we cannot get at it. If, sooner or later, under one circumstance or another, with or without the aid of some kind of stimulus, we can recall the desired knowledge we say it was preserved (or conserved). If we continue, under all circumstances and at all moments, to be unable to recall it we say it is lost, that our memory of it is not conserved. So the notion of conservation of knowledge being something apart from recollection enters even into popular language. What sort of thing conservation is, popular language does not attempt to define. It is clear, however, that we may with propriety speak of the conservation of experiences, using this term in a descriptive sense without forming any definite concept of the nature of conservation. Provisionally, then, I shall speak of conservation of a given experience in this sense only, meaning that the memory of it is not permanently lost but that under certain particular circumstances we can recall it.
Now a large mass of observations demonstrate that there are an enormous number of experiences, belonging to both normal and abnormal mental life, which we are unable to voluntarily recall during any period of our lives, no matter how hard we try, or what aids to memory we employ. For these experiences there is life-long amnesia. Nevertheless, it is easy to demonstrate that, though the personal consciousness of everyday life cannot recall them, they are not lost, properly speaking, but conserved; for when the personal consciousness has undergone a peculiar change, at moments when certain special alterations have taken place in the conditions of the personal consciousness, at such moments you find that the subject under investigation recalls the apparently lost experiences. These moments are those of hypnosis, abstraction, dreams, and certain pathological states. Again, in certain individuals it is possible by technical devices to awaken secondary mental processes in the form of a subconsciousness which may manifest the memories of the forgotten experiences without awareness therefor on the part of the personal consciousness. These manifestations are known as automatic writing and speech. Then, again, by means of certain post-hypnotic phenomena, it is easy to study conservation experimentally. We can make, as you will later see, substantially everything that happened to the subject of the experiment in hypnosis—his thoughts, his speech, his actions, for all of which he has complete and irretrievable loss of memory in a waking state—we can make memory for all these lost experiences reappear when hypnosis is again induced. Thus we can prove conservation when voluntary memory for experiences is absolutely lost. These experiments, among others, as we shall also see, also give an insight into the nature of conservation which is the real problem involved in an investigation into the process of memory.
Before undertaking to solve this problem—so far as may be done—it is well to obtain a full realization of the extent to which experiences which have been forgotten may be still conserved. I will therefore, as I promised you, résumé the experimental and other evidence supporting this principle, making use of both personal observations and those of others.
NOTE—In the following exposition of the evidence for the theory of memory it has been necessary to make use of phenomena subsuming subconscious processes before the subconscious itself has been demonstrated. A few words in explanation of the terms used is therefore desirable to avoid confusing the reader.
Dividing as I do the subconscious into the unconscious and the coconscious, the former is either simply a neural disposition, or an active neural process without any quality of consciousness; the latter is an actual subconscious idea or a process of thought of which, nevertheless, we are not aware. An unconscious and a coconscious process are both, therefore, only particular types of a subconscious process. I might have used the single term subconscious throughout the first seven lectures, but in that case, though temporarily less confusing, the data necessary for the appreciation of the division of the subconscious into two orders would not have been at hand. Typical phenomena having been described as unconscious or coconscious (instead of simply subconscious), the reader will have already become familiar with examples of each type and be thus prepared for the final discussion in Lecture VIII. PROVISIONALLY, these three terms may be regarded as synonyms. To indicate the synonym, the term “subconscious” has often been added in parenthesis in the text to one or other of the subdivisional terms, and vice versa.
[1]. In this connection it is a satisfaction to the author to note that more recently a committee was appointed by the American Psychological Association (December, 1911) to investigate the relation of psychology to medical education. This committee, after an extensive inquiry by correspondence with all the medical schools of the country, has made a report (Science, Oct. 17, 1913) based upon the preponderating opinion of the best medical schools and of the schools as a whole. The second (in substance) and third conclusions reached in the report were as follows:
2nd: For entrance in certain schools requiring a preliminary college training of greater or less length an introductory or pre-medical course in psychology should be required in the same way as they now require chemistry, biology, physics, etc., or, in lieu thereof, a course in the medical schools.
3rd: “It is the belief of most of the best schools that a second course in psychology should precede the course in clinical psychiatry and neurology. This course should have more of a practical nature, and should deal especially with abnormal mental processes and with the application of psychological principles and facts to medical topics. Although this course should deal chiefly with psychopathology, it should not be permitted to develop, or degenerate, into a course in psychiatry, neurology or psychotherapeutics. This course should be clinical in the sense that, as far as possible, clinical material should be the basis of the course, but it should not be clinical in the sense that the students are given particular cases for the purpose of diagnosis or of treatment. The functions of the courses in psychiatry and neurology should not be assumed by this course.”