Psychophysics

“ If the stream of consciousness is nothing but a series of physiological and chemical changes, the laws of the one ought to be identical with the laws of the other, and both with the laws of mechanics, on the mechanical theory. But they are not. Those concise descriptions of mental phenomena which constitute the laws of psychology ought to coincide with those other concise descriptions of fact which constitute the laws of chemistry, if the facts described by the two sciences are the same. ”

“ I have said that I regard psychometry as the key to the development, on rational lines, of the sixth sense. Psychometry itself seems to be a development on the psychic side of that physical sense, which is at once the finest, the most subtle, the most comprehensive, and the most neglected of all the five senses the sense of touch. While distributed over the whole surface of the body, through the nervous system, this sense is more delicate and sensitive in some parts than in others. ”

“ To answer this, we must first remember that Consciousness is a purely subjective process; although we may believe it to be objectively a neural process, we are nevertheless passing out of the region of Physiology when we speak of Feeling determining Action. Motion may determine Motion; but Feeling can only determine Feeling. Yet we do so speak, and are justified. For thereby we implicitly declare, what Psychology explicitly teaches, namely, that these two widely different aspects, objective and subjective, are but the two faces of one and the same reality. ”

“ If we adopt it we shall recognise in sensation a psychical state which has physical processes among its immediate antecedents, and in motor reaction similarly a physical process with psychical antecedents. It is scarcely to be denied that this conception of body and mind, as two things which stand in causal relation, is the hypothesis which most naturally presents itself, when once we have artificially broken up the unity of immediate experience into a physical and a psychical side, and so created the problem of psychophysical connection. ”

“ It is still disputed whether our thoughts, emotions, and volitions are generated through the intervention of material mechanism; whether we have organs of thought and of emotion, in the same sense in which we have organs of sensation. Many eminent physiologists hold the affirmative. These contend, that a thought (for example) is as much the result of nervous agency, as a sensation: that some particular state of our nervous system, in particular of that central portion of it called the brain, invariably precedes, and is presupposed by, every state of our consciousness. ”

“ We hear a sound which we believe to be causally connected with the nightingale, and we see a sight which we believe to be causally connected with a nerve. But in each case it is only the sensation that ought, in strictness, to be called a datum. Now, sensations are certainly among the data of psychology. Therefore all the data of the physical sciences are also psychological data. It remains to inquire whether all the data of psychology are also data of physical science, and especially of physiology. ”

“ Yet the hypothesis of psychophysical parallelism confines us to one or other of the former alternatives: at the same time its unwarrantable identification with psychoneural parallelism—where we find a real correspondence between mind and organism—tends to conceal the gravity of such assumptions. The standpoint of physiology, therefore, must be described not as identical with that of physics, but as intermediate between it and the standpoint of psychology. ”

“ There is a bully physiological laboratory, the sight of which, inaccessible as it is to me in my present condition, gave me a sharp pang. I have blocked out some reading in physiology and psychology which I hope to execute this winter—though reading German is still disgustingly slow.... It seems to me that perhaps the time has come for psychology to begin to be a science—some measurements have already been made in the region lying between the physical changes in the nerves and the appearance of consciousness-at (in the shape of sense perceptions) , and more may come of it. ”

“ What is so clearly true of the nervous apparatus of animal life can scarcely be otherwise than true of that which ministers to the automatic activity of the mind. For, as already shown, the study of psychology has evolved no more certain result than that there are uniformities of mental action which are so entirely conformable to those of bodily action as to indicate their intimate relation to a 'mechanism of thought and feeling,' acting under the like conditions with that of sense and motion. ”

“ Many of the stanchest believers in the soul admit that we know it only as an inference from experiencing its states. In Chapter X, accordingly, we must return to its consideration again, and ask ourselves whether, after all, the ascertainment of a blank unmediated correspondence, term for term, of the succession of states of consciousness with the succession of total brain-processes, be not the simplest psycho-physic formula, and the last word of a psychology which contents itself with verifiable laws, and seeks only to be clear, and to avoid unsafe hypotheses. ”

“ In these volumes an attempt is made to trace objectively the evolution of mind from reflex action through instinct to reason, memory, feeling, and will, from the interaction of the nervous system with its environment. Subjectively, mental states are analyzed, and it is contended that all of them--including those primary scientific ideas, the perceptions of matter, motion, space, and time, assumed in the "First Principles"--can be analyzed into a primitive element of consciousness, something which can be defined only as analogous to a nervous shock. ”

“ Physiology, in a word, will reveal to us the true real elements of the world. Physiological psychology bears to physics in its widest sense a relation similar to that which chemistry bears to physics in its narrowest sense. But far greater than the mutual support of physics and chemistry will be that which natural science and psychology will render each other. ”

“ We can no doubt analyse the content of consciousness during a short interval of time into more or less elementary constituent feelings; but it is not suggested that this psychological analysis will reveal the elements out of whose measure-numbers the atoms or electrons are built. The brain-matter is a partial aspect of the whole mental state; but the analysis of the brain-matter by physical investigation does not run at all parallel with the analysis of the mental state by psychological investigation. ”

“ I fully admit that any exact account of brain states is at present far beyond our reach; and I am surprised that Professor Ladd should have read into my pages the opinion that psychology as a natural science must aim at an account of brain states exclusively, as the correlates of states of mind. Our mental states are correlated immediately with brain states, it is true; but, more remotely, they are correlated with many other physical events, peripheral nerve currents for example, and the physical stimuli which occasion these. ”

“ In concrete science consciousness is drowned in the object, in psychology, on the contrary, the object is drowned in consciousness. The chemist, the physicist, who will turn his attention to consciousness and introduce his psychic states, his moods, dispositions, and intentions as elements into his investigations will hardly be an exact scientist. Not so with the psychologist, he must take the inner world into account, he must deal with consciousness, with moods, with feelings. ”

“ First, there is the theory that it consists merely in the mechanical workings of the brain—a purely physiological theory, which makes the subconscious mind synonymous with certain brain activities—much the same as a series of complex reactions. It is well known that there is a brain-change corresponding to every thought we think; and the nature of the connection between the two has been one of the most debated points in metaphysics, and is one which, if we thoroughly understood it, would doubtless solve in a great measure the nature of life and of consciousness. ”

“ Similarly, the modern psychologist, when confining himself within the limits of positive science, and treating mind phenomenally or empirically, or, in other words, tracing the order of mental states in time and assigning their conditions, takes for granted much the same as physical science does. Thus, as our foregoing analysis of perception shows, he assumes that there is an external cause of our sensations, that there are material bodies in space, which act on our sense-organs and so serve as the condition of our sense-impressions. ”

“ Unlike the physical, the psychic process is finite and final,―it has a beginning and an end, it begins with a purpose, conscious, subconscious, or unconscious, and ends with an adjustment. The psychic process begins as a sensation, and its complete cycle runs its course as an idea and then ends in a volition to act. The stimulus marking the beginning of the psychic process and the act marking the end of the process are physical links of a continuous physical process, the links of which can be traced endlessly in physical terms. ”

“ By the help of this hypothesis of the functional interdependence of matter and spirit, modern physiology is enabled to bring the phenomena of consciousness within the domain of her investigations without leaving the terra firma of scientific methods. The physiologist, as physicist, can follow the ray of light and the wave of sound or heat till they reach the organ of sense. He can watch them entering upon the ends of the nerves, and finding their way to the cells of the brain by means of the series of undulations or vibrations which they establish in the nerve filaments. ”

“ At the end of our journey it is time to return to the question from which we set out, namely: What is it that characterizes mind as opposed to matter? Or, to state the same question in other terms: How is psychology to be distinguished from physics? The answer provisionally suggested at the outset of our inquiry was that psychology and physics are distinguished by the nature of their causal laws, not by their subject matter. At the same time we held that there is a certain subject matter, namely images, to which only psychological causal laws are applicable ”

“ If we look at the matter in this unbiassed light it will appear indubitable that the method of physiological psychology is none other than that of physics; what is more, that this science is a part of physics. Its subject-matter is not different from that of physics. It will unquestionably determine the relations the sensations bear to the physics of our body. ”

“ And just as there is thus a physical psychology, so [p.095] in like manner there is a psychological or epistemological physics, which in its turn is concerned with the indirections, or doors in the panelling, present in all the psychical sciences, for those very physical things quantity and matter. The devil will have his due; even an optimistic theology has to recognize him. And psychology has a sensuous self, the self of the purely sensuous consciousness, which has always involved it in a curious psychical atomism, a projection, in a word, of the physical on the plane of the psychical. ”

“ But by the side of the physiological theory legitimately exist as possibilities a psychological one and a psycho-physical one. It is the doctrine of the latter theories that not only are physical vestiges left behind in the cortex of the brain after every perception, but also psychical dispositions to the formation of ideas and images; and that it is possible for images of all kinds to continue to exist without distinctly attaining to consciousness. ”

“ In spite of the knowledge we have gained of the electrical and chemical phenomena of the central nervous system, we must confess that we know little indeed of the inner nature of the psycho-physical processes. What is happening in the brain—especially in the psycho-motor centres—when we move an arm by means of an act of will? What are the forms of nervous energy which are employed? Are these entirely electrical and chemical forces, the neural impulses being mere electrical currents? Or are there other forms of energy which experimental physiology has not as yet brought to light? ”

“ In a subsequent Problem we shall have to examine the nature of Sensation in its psychological aspect; here we have first to describe its physiological aspect. To the psychologist, a sensation is simply a fact of Consciousness; he has nothing whatever to do with the neural process, which the physiologist considers to be the physical basis of this fact; and he therefore regards the physiologists as talking nonsense when they talk of “unconscious sensations,” the phrase being to him equivalent to “unfelt feelings,” or “invisible light.” ”

“ Assuming, as we must, that our sensations have physical causes, their causal laws are nevertheless radically different from the laws of physics, since the consideration of a single sensation requires the breaking up of the group of which it is a member. When a sensation is used to verify physics, it is used merely as a sign of a certain material phenomenon, i.e. of a group of particulars of which it is a member. But when it is studied by psychology, it is taken away from that group and put into quite a different context, where it causes images or voluntary movements. ”

“ We can also study the capabilities and limitations of the subconscious in carrying on intelligent operations below the threshold of consciousness. Again, we can investigate the phenomena of this kind as met with in the course of clinical observations, and by technical methods of research explore the subconscious and thus explicitly reveal the process underlying and inducing the phenomena. By such methods of investigation the subconscious has been removed from the field of speculative psychology, and placed in the field of experimental research. ”