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Popular Science Monthly/Volume 51/May 1897/Sources of the New Psychology



PSYCHOLOGY did not begin with the development of its own methods or in the psychological laboratory; on the contrary, it has been largely the product of other sciences. In most cases the first impulse to the investigation of psychological phenomena was given by the discovery of sources of error in the other sciences which were due to the scientist himself.

In astronomy Tycho Brahe did not accept his instruments as being correct, but determined their errors; it was not, however, until centuries later that a suspicion arose concerning the possibility of errors in the observer himself.

Astronomers have to record the time of the passage of heavenly bodies across parallel lines in the telescope. When the star is about to make its transit the astronomer begins counting the beats of the clock. As the star approaches and passes the line he fixes in mind its place at the last beat before crossing and its place at the first beat after. The position of the line in respect to these two places gives the fraction of a second at which the transit occurred.

In 1795 the British astronomer royal found that his assistant, working with another telescope at the same time, was making his records too late by half a second. Later on, this amounted to 0.8 second. This difference was large enough to seriously disturb the calculations, and, as the astronomer did not suspect that he himself might be wrong, the blame was laid on the assistant.[2] In 1820 Bessel[3] systematically compared his observations with those of another observer for the same star. They found a difference of half a second. Later he made similar experiments with Argelander and Struve, with the result of always finding a personal difference.

Bessel sought for the cause of this "personal equation" by varying the conditions. He first made use of the sudden disappearance or reappearance of a star instead of steady motion. The personal difference was much decreased. This seemed to indicate that the trouble lay in comparing the steady progress of the star with the sudden beat of the clock. The next step was to change the beats, with the result that for Bessel the observations were made later with the clock beating half seconds than with one beating seconds, whereas Argelander and Struve showed no particular change. One other point was investigated—namely, the effect of the apparent rate of the star; within wide limits the personal equation was not changed.

About 1838 the personal equation began to receive regular notice in astronomical observations, as appears in the publications of Airy[4] and Gerling of that year.[5]

It was natural to wish for a comparison of the astronomer's record with the real time of transit. At the suggestion of Gauss, an artificial transit was arranged by Gerling, the object observed being a slow pendulum. This is probably the first measurement of a reaction time. In 1854 Prazmowski[6] suggested an apparatus carrying a luminous point for a star and closing an electric circuit at the instant it passed the line; a comparison of the true time with the astronomer's record would give the real amount of his personal equation. From this time onward various forms of apparatus were invented and numerous investigations were carried out. The astronomers found that in such observations sometimes the star was seen to pass the line too soon, sometimes too late, and that the error varied with every variation in the method of observing and in the mental condition of the observer.[7]

Let us turn for a moment to another science. The new physiology, begun by the pupils of Johannes Müller, in which the phenomena of life were to be explained by physical and chemical processes, had undergone a remarkable development. Du Bois-Reymond had taught how to apply the experimental methods and apparatus of physics to the study of physiological processes. Soon after this Helmholtz measured the velocity of nervous transmission (1850), an experiment that Johannes Müller had considered hopeless. This involved the construction of the myograph and the application of Pouillet's method of measuring small intervals of time.

The nerves, however, are only the peripheral portions of the nervous system; the desire lay near to measure the time occupied by the brain processes. Such measurements have been (and still are at the present day) impossible by direct physiological methods. It was, however, a sufficiently settled fact that the brain processes are closely accompanied by mental processes. This consideration led to the employment of the time-methods on living human beings. The stimulus was applied to the skin, to the eye, or to the ear, and the time required for the subject to respond by a muscular movement was measured. Since the subject could tell what he experienced under different variations of the experiment it was found possible to measure the time of sensation, of action, etc. The physiological processes corresponding to these mental processes were to some extent known. It was soon discovered, however, that other mental processes—e. g., discrimination, association, etc.—could be introduced in such a way as to be measured.

Beginning with 1865, Donders made a systematic attack on the problem of psychological time-measurements, and was soon followed by Exner. Helmholtz had already directed the experiments of his pupil Exner in measuring the time of sensation, and in 1877 the work of Auerbach and von Kries appeared from his Berlin laboratory.

The interest of the physiologist lay, however, mainly in the deductions to be drawn concerning brain action. Even from the simpler forms of reaction time the amount of physiological knowledge to be obtained is small, and for the more complicated forms it is zero. It was natural, therefore, for physiology to pursue the subject not much further.[8]

Thus the two sciences of astronomy and physiology discovered and developed the methods of investigating mental times; the further development was the task of psychology.

Another source of the new psychology is to be found in the physiological study of the sense organs. The most obvious method for determining the functions of the nerves and end organs of the skin—the nose, the ear, or the eye—is to ask the living subject what he feels when various stimuli are applied. In this way there has arisen a large body, of knowledge concerning the sensory functions of the nervous system. In this form, however, the problem is a purely psychological one. To inquire if the skin "feels" heat is, from a physiological point of view, an indirect question. Physiologically, the nerves of the skin may respond to heat by some chemical process; that they do so respond may be inferred on the hypothesis of a correspondence between the occurrence of a sensation of heat and the action of the nerve. The direct question is one of psychology; it is asked by physiology for its own purposes, and the psychological data are collected as long as they are of use in this way. Physiology, however, is "physics and chemistry of the body," and as soon as psychological data cease to afford physical deductions the interest of the physiologist generally ceases. The study of the psychology of sensation and action, however, has formed and still forms an important portion of physiology.

Historically considered, the study of the sensations of the skin received its first great impulse from Ernst Heinrich Weber's monograph, Tastsinn und Gemeingefühle.[9] This has been followed by the work of a host of investigators from the laboratories of Ludwig, Du Bois-Reymond, and their pupils.[10]

The physiology of the eye originated much of the psychology of sight. Concerning the functions of the optical system, physiology can scarcely be said to have gone beyond the dioptrics of the eye. Nearly all further knowledge consists of deductions from the mental experiences of the subject. For example, physiology knows almost nothing concerning the functions of the retina. Psychologically, however, the color sensations and their combinations can be accurately measured. It is true that the investigations of color vision have been and are mainly carried out by physiologists and physicists; but the point of view has become primarily a purely psychological one. This is strikingly exemplified in the researches of König, from which physiological deductions are practically excluded. For the various other phenomena, such as those of the optical illusions, of monocular and of binocular space, we have at present no hope of anything beyond a psychological knowledge, and the investigations of Hering, Helmholtz, and others can be regarded as direct contributions to psychology.

There is a third science whose influence is to-day the strongest of all. Physics is theoretically the co-ordinate science to psychology. Every direct experience has an objective, or physical, and a subjective, or psychical, side. Again, the fundamental science of Nature is physics, that of Mind is psychology. Practically, however, psychology receives from the most powerful science of modern times an invaluable protection and an uninterrupted series of scientific gifts. The photometry of Lambert led not only to the methods of modern technical photometry but also to the measurement of our sensations of light, while the law of relativity of sensations had been—before Fechner—established for lights by Bouguer, Masson, Arago, Herschel, and Steinheil. The study of the errors of observation in physics and astronomy has led not only to the science of physical measurements, but also to that of psychological measurements. Newton, Young, and Maxwell began not only the science of ether vibrations, but also the science of sensations of color. The laws of mechanics apply not only to inanimate objects but also to the results of our own volitions. In fact, in every department of psychology, progress has been and still is closely dependent on the achievements of physics and technology.

Psychology has not only received most of its methods and much of its material from physics; it has for the first time in history reached through physics a definite conception of its own problem. The older psychology and philosophy had always maintained the necessity of directly investigating the facts of consciousness. The standpoint was simple enough, but, as no scientific methods of doing so were developed, the whole problem remained vague and unsatisfactory. Among the proposals for a better state of affairs was that of first investigating the nervous system and then deducing psychological laws therefrom. The brain was to be accurately mapped out into faculties, the paths of nervous currents were to be traced along various fibers, and the interaction of nervous molecules was to be known in every particular; it was even expected that various cells could be cut out, with a memory or a volition snugly inclosed in each. In other words, there was to be no psychology except on the basis of a fully developed brain physiology. Unfortunately, very little has been ascertainable concerning the finer functions of the nervous system. Aside from a general knowledge that the cerebellum has to do with co-ordination of movements, the convolutions of Broca have to do with speech, and similar facts, nothing of even the remotest psychological bearings has been discovered concerning the functions of the brain. The roseate hopes of those who expected a new psychology out of a "physiology of mind" were totally disappointed. In the effort for something new, however, the psychologist supplied the data concerning the "molecular movements" in the brain out of his own imagination; the familiar facts of mind were retold in a metaphorical language of "nerve currents," "chemical transformation," etc., of which not one particle had a foundation in fact. The physiology of mind started with an impossibility and ended with an absurdity.

It is to be noted that these statements refer to investigations of and speculations on the brain for psychological purposes. For physiological purposes the case is utterly different. The development of brain anatomy and of the knowledge concerning the localization of cerebral functions are among the greatest achievements of modern time.[11]

Moreover, the collection of facts and the development of theories of the nervous activities accompanying mental phenomena has given rise to the science of physiological psychology.[12]

With these sciences, however, the psychologist has comparatively little to do. The study of brain function has not contributed a single fact to our knowledge of mental life; the deductions of physiological psychology concerning nervous function have begun with the facts of experimental and observational psychology, and are still so unsettled as not to allow additional deductions backward.

While this was going on, physics had through Helmholtz,[13] Mach,[14] and others gradually come to a clear understanding of the relation of its facts to the immediate facts of consciousness. Direct experience as present in our sensations was accepted as supplying the facts of physics. For example, in measuring the length of a bar, a visual sensation, the scale of measurement, was applied to another visual sensation, the bar. Indeed, as was clearly recognized, every direct measurement of physics was primarily a comparison between sensations—in other words, a psychological measurement. From this combined measurement the physicist reduced as much as possible the psychological elements; it was but a step for the psychologist to reduce the physical elements in order to have a psychological measurement.[15] This step made psychology for the first time a science in the full meaning of the term, with all the previous achievements of physics for its use.

With a real science of the facts of consciousness at hand, the attempt at a "mental physiology" appears as absurd as an attempt to establish a science of meteorology from the twitterings of the birds—especially when the birds are imaginary ones. The physicists have thus not only given to the new psychology its basis, but have also freed it from the rubbish of an overheated imagination.

There is still another source which we must consider, namely, the old psychology. By the "old psychology" we mean psychology before the introduction of experiment and measurement; in its last forms it is the psychology of the Herbartians or of the English associationalists.

We have already seen how the fundamental method, that of observation, was established by the old psychology. The method of direct observation of mental life is the only possible one, and until it had received a firm basis any science of psychology was impossible. As has been explained in Part I, all the other methods of psychology are only refinements of this method. The new psychology is thus merely a development on the basis of the old; there is no difference in its material, no change in its point of view, and no degeneration in its aim. What the old tried to do, namely, to establish a science of mind, and what it did do, as far as its means allowed, the new psychology with vastly improved methods and facilities is striving to accomplish.

This close connection, however, must not involve us in a false estimation of the direct results accomplished by the old psychology. The method of unaided observation was applied to exhaustion, and the later works contained little more than the earlier ones. Indeed, the final sum total of psychological knowledge acquired by this method can be stated to be a mass of ingenious speculations, of endless discussions, and of true and untrue facts; even such achievements as the laws of association have, in the light of newer methods, been shown to be merely superficial arrangements of facts. It has been claimed that unaided observation has yielded valuable storehouses of facts, and it furnishes a special satisfaction to some people at the present day to point out guesses of this older psychology forestalling achievements of the newer science. Among the clever observations concerning facts of mental life and the ingenious guesses at their laws, there are and must be some which are ultimately found to be partially or wholly correct. As Helmhoitz remarks: "It would be a stroke of skill always to guess falsely. In such a happy chance a man can loudly claim his priority for the discovery; if otherwise, a lucky oblivion conceals the false conclusions. The adherents of such a process are glad to certify the value of a first thought. Conscientious workers, who are shy at bringing their thoughts before the public until they have tested them in all directions, solved all doubts, and have firmly established the proof; these are at a decided disadvantage. To settle the present kind of questions of priority only by the date of their first publication, and without considering the ripeness of the research, has seriously favored this mischief.

"In the type-case of the printer all the wisdom of the world is contained which has been or can be discovered; it is only requisite to know how the letters are to be arranged. So, also, in the hundreds of books and pamphlets which are every year published about ether, the structure of atoms, the theory of perception, as well as on the nature of the asthenic fever and carcinoma, all the most refined shades of possible hypotheses are exhausted, and among these there must necessarily be many fragments of the correct theory. But who knows how to find them?

"I insist upon this in order to make clear to you that all this literature, of untried and unconfirmed hypotheses, has no value in the progress of science. On the contrary, the few sound ideas which they may contain are concealed by the rubbish of the rest; and one who wants to publish something really new—facts sees—himself open to the danger of countless claims of priority unless he is prepared to waste time and power in reading beforehand a quantity of absolutely useless books, and to destroy his reader's patience by a multitude of useless quotations."[16]

In order to give a psychological illustration, I will refer to the case of mediate association of ideas.[17] The existence of such associations was discovered in the course of an extended experimental investigation of the manner in which ideas were associated. It was proved, for the first time, that such associations are made. A single personal observation of this sort is to be found in Hamilton's works. A still earlier one is reported from Hume, and a favorable perusal of the works of Aristotle would probably reveal something similar. Such cursory observations, fruitless and unconfirmed, do not entitle the makers to any special credit. The credit of an experimental discovery remains with the discoverer, regardless of previous guesses that may have hit the truth.

The debt of the new psychology to the old psychology of the past does not involve any claims by the "sensation-psychology" of the present. Among the pupils of the old psychology there were necessarily many who grew up in ignorance of the new, or who did not learn of its existence until too late for changing the mode of thought. Just as the old psychology led to an improved science on the part of the progressive men, so it led to a degenerated form on the part of the others. Unable to grasp and to apply the methods of true science, these men can not even understand what the new is all about; and in their attempt to do something new they have fallen into the absurdities of "psychical research," or "experimented" with spiritualistic mediums, or gathered "statistics" concerning ghosts, or interviewed the several personalities of the hypnotic subject.

The older psychology, with its traditions and its dignity, was a discipline to be treated with filial consideration and respect; but the latest "sensation-psychology," plunged in the dregs of all the mysticism and superstition of the middle ages, not only contributes nothing to the progress of science, but arouses in opposition to it all the ghosts of the witches' caldron.

Summarizing, we are entitled to say that the new psychology is the old psychology in a new phase of development; that the impulses to this development came from physics, physiology, and astronomy; and that the resulting application of the best methods of modern science to the great problems handed down from the past is what makes the new psychology a true science worthy of its origin.


  1. From a forthcoming work, The New Psychology (London, Walter Scott; New York, Scribner).
  2. Greenwich Astronomical Observations, 1795, vol. iii, pp. 319, 339.
  3. Astronom. Beobacht. d. Sternwarte zu Königsberg, Abth. VIII, p. iii; Abth. XI, p iv; Abth. XVIII, p. iii.
  4. Greenwitch Astron. Observations, 1838, p. xiii.
  5. Astron. Nachrichten, 1838, vol xv, p.249.
  6. Comptes rendus, 1854, vol. xxxviii, p.748
  7. For the history of the personal equation, see Sanford, Personal Equation, Am. Jour. Psych., 1888, vol. ii, pp. 3, 271, 403.
  8. For the historical account of experiments on reaction time, see Buccola, La legge del tempo nci fenomeni del pensiero, Milano, 1883, and Ribot, La Psychologie allemande contemporaine, Paris, 1885; for a summary, with literature, see Jastrow, Time Relations of Mental Phenonmena, New York, 1890.
  9. Wagner's Handwörterbuch d. Physiologie, 1851, vol. iii (2), p. 561; also separate.
  10. For summaries and references, see Funke und Hering, Physiologie der Hautempfindungen und der Gemeingefühle, Herman's Handbuch der Physiologie, 1880, vol. iii (2), p. 287; and Beaunis, Nouveaux éléments de physiologie humaine, vol. ii, Paris, 1888.
  11. For a historical sketch and an account of the latest remarkable discovery, see Flechsig, Gehiru und Seele, Leipzig, 1896.
  12. As a representative work see Exner, Entwurf zu einer physiologischen Erklärung der psychischen Erscheinungen, i. Theil, Lepzig, 1894. For a convenient summary see Ziehen, Leitfaden der physiologischen Psychologie, second edition, 1893, also translated
  13. Helmholtz, Ueber das Ziel die Fortschritte der Maturwissenschaft, Populäre wiss. Vorträge, Braunschweig, 1871. Helmholtz, Die Thatsachen in der Wahrnehmung, Leipzig, 1879.
  14. Mach, Die Mechanik in ibrer Entwickelung, Leipzig, 1883, second edition, 1889; also translated into English, Chicago, 1895 (Mach's earlier monographs are mentioned in the preface). Mach, Beiträge zur Analyse der Empfindungen, p. 141, Jena, 1886.
  15. The psychological standpoint has been clearly stated by Wundt, Ueber die Messungen psychischer Vorgänge, Philos, Studien, 1883, vol. iv, p. 1; Weitere Bemerkungen über psychische Messungen, Philos, Studien, p. 463; Ueber die Entheilung der Wissenschaften, Philos, Studien, 1889, vol. v, p. 1; Ueber die Definition der Psychologie, Philos, Studien, 1896, vol. xii, p. 1; Ueber naiven und kritischen Realismus, Philos, Studien, 1896, vol. xii, p. 307. I have followed Wundt in The Problem of Psychology, Mind, 1891, vol. xvi, p. 305; Psychological Measurements, Philosophical Review, 1893, vol. ii, p. 677.
  16. Helmholtz, Popular Lectures, Second Series, p. 228. New York, 1881.
  17. The idea, C, follows a totally unrelated idea, A. A and C had previously been independently associated with B, but now B is not though of, or is entirely forgotten.