# Popular Science Monthly/Volume 66/December 1904/The Conceptions and Methods of Psychology

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* THE CONCEPTIONS AND METHODS OF PSYCHOLOGY.
By Professor J. McKEEN CATTELL,
COLUMBIA UNIVERSITY.
ONE of the verses in the treasure-house of Greek letters warns us against calling any man happy before he is dead. The greatest living English author lets one of his favorite characters say: 'But does incessant battling keep the intellect clear?' Such reflections may well lead us to distrust any attempt, by one in the ranks, to sum up the fundamental conceptions and methods of a science, especially of a young and growing science. It may be the prerogative of the student of psychology to write the biography of an infant, but he has not hitherto penetrated very far into its real life. I disagree completely with the eminent psychologist to whom the plan of this great congress is chiefly due when he claims that 'the presuppositions with which a science starts decide for all time the possibilities of its outer extension.' Sciences are not immutable species, but developing organisms. Their fundamental conceptions and methods at any period can only be approached by a research into work actually accomplished. Had time and circumstance permitted, I should have attempted to make an inductive study of the contents and methods of psychology rather than to prepare three quarters of an hour of generalities and platitudes. But as even the pedant knows, 'die Kunst ist lang, und kurz ist unser Leben.' The court poet must console himself for the deficiencies of his ceremonial verses by reflecting on the honor of being permitted to write them.
The concept of a science is an abstraction from an abstraction. The concrete fact is the individual experience of each of us. Certain parts of this experience are forcibly and artificially separated from the rest and become my science of psychology, your science of psychology, his science of psychology. From all these individual sciences, shifting not only from person to person but also from day to day, there arises by a kind of natural selection a quasi objective science of psychology. In a well-bred science, such as chemistry, the conventions have become standardized; the dogmas impose themselves on the neophyte. But projectiles as small as ions or electrons break up the idols, and the map ​of science is remodeled more quickly and completely than the map of Asia.
Psychology has never had a well-defined territory. As states of consciousness appear to be less stable and definite than the objects of the material world, so the science of psychology is more shifting in its contents and more uncertain in its methods than any physical science. "We are told indeed in our introductory text-books that psychology is the science of mind and that mind and matter are the most diverse things in the world. It is said further that psychology is a positive science and is thus clearly distinguished from the normative disciplines, such as logic and ethics. Words are also used to set psychology off from sociology, history, philology and the rest. But while all these verbal definitions may satisfy the college sophomore, they must be perplexing to the candidate for the doctor's degree.
The distinction between mind and matter is one of the last words of a philosophy which does not yet exist, rather than an axiom of every-day experience on which preliminary definitions may be based. We can not rest satisfied with an empirical psychology in which the distinction is self-evident, an epistemology in which it is explained and a metaphysics in which it disappears. It may be that we follow Descartes rather than Aristotle in our psychology, not so much from the needs of the science itself as from the demands of the church, on the one hand, and of physical science, on the other. The church required souls that might be saved or damned; physics wanted a world independent of individual perception, and as the methods of exact science were extended to the human body it became a part of the physical system.
To us who have been brought up in the orthodox tradition, the views of some of those who have passed from natural science to metaphysics seem decidedly naive. Thus Mach entitles the concluding section of his Science of Mechanics 'The Relations of Mechanics to Physiology,' when he is discussing not the question as to whether vital phenomena may be reduced to the laws of matter in motion, but the relations between sensations and the physical stimulus. Pearson tells us in his Grammar of Science that if the cortex of one brain were connected with another by a commissure of nerve substance, there would be 'physical verification of other consciousness.' Ostwald lets energy do hermaphroditic service in the physical and the extra-physical households.
But it is not certain that such ingenuous commingling of the mental and the physical worlds is more repugnant to common sense or natural science than the logical subtleties of the schools, which undertake to define, relate or obliterate them. It is generally assumed that a psychologist must be either an interactionist or a parallelist. ​According to the definitions with which our psychologies start, it is indeed true that mind and matter must either interact or in some way correspond without interaction. If the psychologist asserts that each brain is a center for the creation of new energy or for interference with the configuration of a material system, he obviously subverts the principal generalizations of physical science. He doubtless has a right to do so, but in the same sense as the cow has a right to stop the locomotive engine. If, on the other hand, the psychologist modestly admits that mind does not affect the physical order, he runs counter to the principal generalization of biological science. If pleasure and pain, memory and forethought, are of no use in the struggle for organic survival, why should they ever have evolved?
It requires less temerity to question the theories of biology than to deny the laws of physics. The survival of the fit may be regarded as a truism rather than as a discovery, if we call that fit which does survive. But fitness of this kind is so protean in its manifestations in organic nature that the formula becomes somewhat vague. If an animal is inconspicuously colored, it is protective coloration and so useful; if conspicuously colored, it is directive coloration and so useful. It is somewhat difficult to guess the utility of the fantastic shape and color of each deep-sea fish that lives in perpetual darkness. Then there are admittedly correlated variations, by-products of evolution, diseases and the like; it may be that consciousness is that sort of thing. If some kinds of consciousness, as the sense of beauty, are of no use in the struggle for existence, all the rest may be equally useless—an efflorescence exhibited when there is friction due to lack of adjustment between the organism and its environment. Finally, and most plausibly, it may be argued that minds have evolved in answer to final causes, and that organic evolution must adopt the principles of psychology rather than prescribe to it.
The interactionist seems to be in a worse plight than the parallelist in the conflicts with our sister sciences, but the case is different before the court of common sense. The present writer can not conceive how the parallelist gets outside the limits of consciousness. Why does he want any thing to run parallel with the only thing he knows? He becomes at once a subjective idealist, and there may be no harm in that. But when the subjective idealist wants to live in a world with other men, he reinvents the distinctions that he had verbally obliterated. What he knows about the physical world is what his senses and the physicists tell him; if he likes to call it all consciousness or the unconscious, mind-stuff, will or God's thought, this may be emotionally stimulating, but no fact or law is thereby altered. The world may be God's thought, without in the least preventing the parallelist from thinking illogically. ​If clarified experience is subverted by logic, we can of course become sceptics; but it is safer and wiser to wait awhile. Experience may become more clarified, our premises may prove to be at fault, even our syllogisms may be false. When it is said that a psychologist must be either an interactionist of a parallelist, and we find insurmountable difficulties in the way of his being either, the trouble may be with the original assumptions. Matter and consciousness may not be two entities set over against each other. A perception may be both a part of my consciousness and a part of the physical world; an object may be at the same time in a world of matter in motion and in the microcosm of my individual mind. As my colleague, Professor Dewey, starting from an idealistic standpoint, claims, we may simply be giving different names to activity when it is tensional and when it is relatively stable; or as my colleague, Professor Woodbridge, starting from a realistic standpoint, suggests, the relation of consciousness to objects may be analogous to that of space to objects.
As I have said, the relations of mind to body and the distinction between consciousness and matter are the last word of a philosophy that is not yet written, and I have no competence or wish to discuss them here. But the task has been assigned to me of considering the scope, conceptions and methods of psychology, and it is my business to define the field of psychology or to acknowledge my inability to do so. I must choose the latter alternative. I can only say that psychology is what the psychologist is interested in qua psychologist. If it is said that this is tautological, it may be replied that tautology is characteristic of definitions. If psychology is defined as the 'science of mind' or, what in my opinion is better, 'the science of minds' the tautology is equal, and it appears to be more possible to determine by an inductive study the professional interests of psychologists than to define the nature of mind or consciousness. Further, I am not convinced that psychology should be limited to the study of consciousness as such, in so far as this can be set off from the physical world. Psychology apart from consciousness is doubtless an absurdity, but so also is mathematics or botany. I admire the products of the Herbartian school and the ever-increasing acuteness of introspective analysis from Locke to Ward. All this forms an important chapter in modern psychology; but the positive scientific results are small in quantity when compared with the objective experimental work accomplished in the past fifty years. There is no conflict between introspective analysis and objective experiment—on the contrary, they should and do continually cooperate. But the rather widespread notion that there is no psychology apart from introspection is refuted by the brute argument of accomplished fact.
​It seems to me that most of the research work that has been done by me or in my laboratory is nearly as independent of introspection as work in physics or in zoology. The time of mental processes, the accuracy of perception and movement, the range of consciousness, fatigue and practise, the motor accompaniments of thought, memory, the association of ideas, the perception of space, color-vision, preferences, judgments, individual differences, the behavior of animals and of children, these and other topics I have investigated without requiring the slightest introspection on the part of the subject or undertaking such on my own part during the course of the experiments. It is usually no more necessary for the subject to be a psychologist than it is for the vivisected frog to be a physiologist.
James and Wundt agree in telling us that the experimental method is chiefly of use as a servant of introspection; indeed James says that there is no 'new psychology,' 'nothing but the old psychology which began in Locke's time, plus a little physiology of the brain and senses and theory of evolution, and a few refinements of introspective detail.' But our leaders in psychology have become our leaders by belying such partial statements. Although neither Wundt nor James has attempted any considerable experimental research, yet we look up to them as the founders of modern psychology. Wundt's original and laborious Physiologische Psychologie, the Leipzig laboratory and the Philosophische Studien have been in large measure the foundation stones of experimental psychology. The broad opportunistic treatment of James, instinct with genius and fearless of logical inconsistency, has been of immense service in freeing psychology from traditional fetters. I see no reason why psychology, at least the psychology of twenty years ago, may not be said to be the subjects treated in James's Principles of Psychology and Wundt's Physiologische Psychologic with such additional subjects as other psychologists have included or might have included in their treatises.
When the introspective purist says that the treatises of Wundt and James are potpouris of sciences, or that the kind of work that some of us have attempted to do belongs to physiology or to anthropometry or nowhere in particular, there is a natural temptation to reply that much of introspective and analytic psychology belongs to art rather than to science. Such things may be ingenious and interesting, like the personae of Bernard Shaw or the mermaids of Burne Jones, but we don't expect to meet them in the street. An attitude of this kind would, however, be as partial as that which it seeks to controvert. Let us take a broad outlook and be liberal in our appreciation; let us welcome variations and sports; if birth is given to monstrosities on occasion, we may be sure that they will not survive.
Any attempt at a priori limitation of the field of a science is futile. ​Even if, for example, consciousness and matter in motion were distinct and distinguishable, this would be no argument against a science of physiological psychology. Cerebral and psychical phenomena form one series, and if we have at present no adequate science which concerns itself with this series, it is owing to ignorance of facts, not at all to logical limitations. Matter, time, space and the differential calculus may be as disparate as possible, but are brought together in the science of physics. If the psychologist can not be shut out of the physical world, still less can he be excluded from the sphere of the so-called normative sciences. If any one takes a modern work on ethics or esthetics and tries to separate the treatment of 'what is' from that of 'what ought to be' he will find himself engaged in an idle task.
It appears that the limits of a science are set largely by a psychological constant. A single science has practically the range that can be covered by a single mind or man. From Aristotle to Hobbes and Descartes there were philosophers who could master nearly the whole range of knowledge and advance it in whatever direction they cared to turn. But even in this period as knowledge accumulated, specialization began, and we find astronomers, anatomists and other students of particular sciences. After Galileo and Newton the physico-mathematical sciences became completely divorced from the descriptive natural sciences, while psychology remained under the shelter of philosophy. It was only in the second half of the nineteenth century that the accumulation of certain facts and theories warranted their becoming the chief interest of a psychologist, and even yet it is more usual for a man to pass through a psychological period than to be a permanent psychologist.
While the first result of increased knowledge has been the establishment of a number of sciences—say a dozen or a score—which have secured proselytes and to a certain extent limited and directed their activities, the further increase of knowledge must break down the artificial limitations. The late emergence of psychology has made easy an elective selection of material. We not only have psychologists who are also philosophers, but psychologists who are also physiologists, anatomists, pathologists, zoologists, anthropologists, philologists, sociologists, physicists or mathematicians. Psychology is and will increasingly become united with professions and arts, with education, medicine, music, painting and the rest. Even sciences remote from psychology, astronomy, for example, may have sufficient points of contact to occupy the entire time of a specialist. We not only have combinations between the orthodox sciences, but cross-sections through them, which may to advantage occupy the student, and which have full rights to be ranked as sciences. The phenomena of vision, for example, are scattered among the sciences of psychology, physics, physiology, anatomy, ​anthropology, zoology, embryology, pathology, chemistry, mathematics, etc.; they are important factors in certain fine and industrial arts; they are the basis of one of the most important medical disciplines. Why should not a man be a 'visionologist' or 'sightonomer'? When President Hall gives us an original and unique book on adolescence, nothing is gained by attempting to assign it to one of the conventional sciences. The work of Dr. Galton appears to me to be particularly unified, but it does not belong to psychology, nor to any other science. Why not call him an opportunist, or a liberal unionist, or a Galtonist, or better still call him no name at all?
In objecting to an artificial limitation of the field of the psychologist, I by no means want to aggrandize his office or to let psychology eat up the other sciences. The student of psychology is limited by the capacity of the human mind and of his own particular mind; he can, on the average, cover a range about as large as that of the student of any other science. If he would gladly get, he would also gladly give. If he is an imperialist who would set his flag on every corner of the earth, he yet tears down no other flag and welcomes the invasion of his own territory by every science.
As I claim for psychology the freedom of the universe in its subject-matter, so I believe that every method of science can be used by the psychologist. The two great achievements of science have been the elaboration of the quantitative method on the one hand and of the genetic method on the other. The uniformity of nature and the rationality of things are here presented in their most convincing, or at all events most plausible form. It would be an irreparable limitation if either of these methods did not apply in psychology. In my opinion they not only do obtain but must obtain. The mental and the physical are so inextricably interfused that quantitative and genetic uniformities could not exist in the physical world if absent from consciousness. If our mental processes did not vary in number, if they did not have time, intensity and space relations, we should never have come to apply these categories in physics, chemistry or astronomy. I am not prepared to attempt to clear up the logical questions involved; when water is muddy it is often wise to wait for it to settle rather than to keep stirring it up.
Under the conditions of modern science nearly all observations are experiments and nearly all experiments are measurements. A sharp distinction is usually drawn between an experiment and an observation. Thus Wundt, following Mill and other logicians, defines an experiment as an observation connected with an intentional interference on the part of the observer in the rise and course of the phenomena observed. But it is as properly an experiment to alter the conditions of observation as to alter the course of the phenomena observed. If the astronomer ​goes to the ends of the earth and photographs a solar eclipse, making all sorts of measurements and calculations, we may say that this is an observation and not an experiment, but we have not made a useful definition; neither do we gain anything by deciding whether it is an experiment when a baby pulls apart a doll to see what is inside. The real distinction is between the casual experimenting and observing of daily life, and the planned and purposive experiment and observation of science. Science is experimental qua science.
I consequently object to making experimental psychology a branch of psychology. It is a method in psychology, which is extended just as rapidly as psychology becomes a science. The purely introspective or analytic observer does, according to the current definition' continually make experiments, because his introspection itself alters the process that he is observing, thus sometimes making his observations invalid as a description of natural conditions. On the other hand, the student in the laboratory may measure the process without any introspection or interference with it, and this may not be technically an experiment at all, but it gives a scientific description of the normal course of mental life. We are told that Adam gave a very appropriate name to the hog; science is not always so fortunate in its nomenclature.
Most experiments, letting experiments mean attempts to increase scientific knowledge, are also measurements. Measurement is only a description; but it has proved itself to be the most economical, wide-reaching and useful form of description. What language was for the evolution of primitive man, measurement is for the advance of modern science. As a word selects similarities and ignores differences, so a measurement selects certain similarities from the concrete manifoldness of things. That such a great part of the world can be described in terms of a few units of measurement, and that this description should lead to such useful applications, is truly marvelous and admirable. As I am writing these paragraphs, I have received a manuscript in which the author explains that the fact that the earth rotates on its axis in twenty-four hours, not varying a second from day to day, is a conclusive proof that it was created and set rotating by a benevolent being. If the days were shorter, he says, we could not get our work done, and if the days were longer, we should be too tired by night. It almost seems as though the world were made in such comparatively rational fashion in order that we may measure it.
The physicist counts, and he measures time, space and energy. He has intractable matter with its seven and seventy elements, and he may come across a substance as complex and perplexing as radium. But by and large he can describe his world in certain quantitative formulas. It is true that he accomplishes this in part by unloading on psychology qualitative differences, such as colors and tones. So much the ​more satisfaction to us if we can reduce them to quantitative order. Perhaps we shall have only partial success; but it may fairly be urged that psychology has done as much in this direction in fifty years as physics accomplished to the time of Galileo or chemistry to the time of Lavoisier.
The psychologist counts and he measures time, space and intensity. Even if it were true—I think it is not true—that mental magnitudes are not measurable, it would none the less be the case that mental processes are described in quantitative terms. This is attempted and accomplished in most of the researches published in our psychological journals. They describe measurements and the correlation of quantities; they show that a mental mechanics is more than a possibility.
The physical sciences have been primarily quantitative and the biological sciences are primarily genetic, but the physical sciences must become genetic and the biological sciences must become quantitative. Psychology is from the start both quantitative and genetic. It may indeed be claimed that it is the science in which the genetic method has the most complete application. Every mental state and every form of activity is the result of development from previous conditions. If explanation, as distinguished from description, is possible anywhere in science it is possible here. It is certainly difficult to penetrate by analogy into the consciousness of the lower animals, of savages and of children, but the study of their behavior has already yielded much and promises much more. Although those who make their psychology coterminous with introspection can not enter far into this field, they still have their own genetic problems. In whatever direction we turn the harvest is waiting; it is only the reapers who are few. Almost every observation, experiment or theory of organic evolution offers parallel problems for the psychologist. The development of the individual opens questions more numerous and more important for psychology than does the development of the body for other sciences. Senile, degenerative and pathological conditions are all there for psychological investigation. The evolution of society and the inter-relations of individuals are being gradually brought within the range of genetic psychology. It is quite possible that the chief scientific progress of the next fifty years will be in this direction.
The problems of psychology are certainly made endlessly complex by the fact that we have to do not with the development and condition of a single mind or individual, but with innumerable individuals. The traditional psychology has been disposed to ignore individual differences; but in attempting to prescribe conditions for all minds, it becomes schematic and somewhat barren. It is surely wasteful to select those uniformities that are true for all and to throw away those differences which are equally fit material for scientific treatment. ​Linnæus instructed his pupils to attend to species and to ignore varieties, and this in the end tended to make systematic botany and zoology unfruitful. If the zoologist had limited his work to the discovery of facts that are true for all animals and had ignored the differences between animals, he would have done something analogous to what the psychologist has actually done.
It may be that individuals can not be grouped into species or even varieties, but animals and plants are separated into species in accordance with the noticeable differences between them, and there are as many degrees of just noticeable difference between men as between related species. We have in any case the different species of the animal series and the different races of men for psychological study; it may be that instincts and mental traits have specific or racial significance for the zoologist or anthropologist. We have the infant, the child, the adolescent and the aged; we have the two sexes; we have the geniuses, the feeble-minded, the criminals and the insane—complex groups to be sure, but open to psychological investigation. It may be that mental imagery or types of character will give workable groups. But even if mental traits and their manifestations are continuous, we can study the continuum. The study of distribution and correlation appears to open up subjects of great interest and having important practical applications.
The question of the practical applications, of psychology is the last which I shall touch. There are those who hold that there is something particularly noble in art for art's sake or in science divorced from any possible application. We are told of the mathematician who boasted that his science was a virgin that had never been prostituted by being put to any use. It is doubtless true that science justifies itself if it satisfies mental needs. It may also be true that pure science should precede the applications of science. But of this I am not sure; it appears to me that the conditions are most healthful when science and its applications proceed hand in hand, as is now the case in engineering, electricity, chemistry, medicine, etc. If I did not believe that psychology affected conduct and could be applied in useful ways, I should regard my occupation as nearer to that of the professional chess-player or sword swallower than to that of the engineer or scientific physician.
It seems quite obvious that such knowledge as each of us has of his own perceptions, mental processes and motor responses and of the reactions and activities of others, is being continually used, more continually indeed than any other knowledge whatever. This knowledge is partly organized into reflexes and instincts; it is in part acquired by each individual. Control of the physical world is secondary to the control of ourselves and of our fellow men. The child must observe ​and experiment to fit itself into the social order, and we are always experimenting on it and trying to make it different from what it is. All our systems of education, our churches, our legal systems, our governments and the rest are applied psychology. It may be at present pseudo-science, in the sense that we have drawn conclusions without adequate knowledge, but it is none the less the best we can do in the way of the application of systematized knowledge to the control of human nature.
It certainly is not essential and perhaps is not desirable for every mother, for every teacher, for every statesman, to study psychology, especially the kind of psychology at present available. It is not necessary for a man to be either a psychologist or a fool at forty; he may, for example, be both. But surely it is possible to discover whether or not it is desirable to feed a baby every time it cries, to whip a boy when he disobeys or to put a man in prison when he breaks a law. If each man were given the work he is most competent to do and were prepared for this work in the best way, the work of the world all the way from the highest manifestations of genius to the humblest daily labor would be more than doubled. I see no reason why the application of systematized knowledge to the control of human nature may not in the course of the present century accomplish results commensurate with the nineteenth century applications of physical science to the material world.
The present function of a physician, a lawyer, a clergyman, a teacher or a man of business is to a considerable extent that of an amateur psychologist. In the inevitable specialization of modern society, there will become increasing need of those who can be paid for expert psychological advice. We may have experts who will be trained in schools as large and well-equipped as our present schools of medicine, and their profession may become as useful and as honorable. Such a profession clearly offers an opportunity to the charlatan, but it is not the only profession open to him. For the present the psychological expert should doubtless be a member of one of the recognized professions who has the natural endowments, special training and definite knowledge of the conditions that will make his advice and assistance of value. But in the end there will be not only a science but also a profession of psychology.