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Popular Science Monthly/Volume 73/August 1908/The Movement Towards Physiological Psychology III

< Popular Science Monthly‎ | Volume 73‎ | August 1908

By Professor R. M. WENLEY



LOTZE'S (1817-81) career as an author opened in 1841, and his psychological contributions relevant to the present theme came to an end practically in 1852. Thereafter, save for a few articles,[1] he devoted himself to the elaboration of his highly significant philosophical system. He therefore antedated the work of Helmholtz. A prominent figure in the bitter controversy over vitalism and materialism (1817-60), he suffered grave misunderstanding; nevertheless, thanks to lapse of time, his psychological position admits of no doubt.

The son of a physician, Lotze entered the University of Leipzig to prepare for the paternal profession. Under the influence of Weisse he became interested in philosophy, and, upon graduation, qualified as Docent in both the medical and philosophical faculties. Till 1852 the studies proper to the former predominated, philosophy claimed him later, and his system represents more symptomatically than any other the stress resultant upon the cross-currents of modern thought. It is meaningful that he occupied successively Herbart's chair at Göttingen and Hegel's at Berlin.

In 1842 he took a decided stand, or even lead, in the vitalist controversy,[2] and also published his "General Pathology and Therapeutics as Mechanical Sciences." His "General Physiology of the Corporeal Life "appeared in 1851 and, in the next year, the work of importance for us now—"Medical Psychology, or Physiology of the Soul." Viewed in the perspective of cultural development, especially in Germany, his position seems to me quite evident. Here is his own statement of it:

We have two kinds of scientific knowledge. We know, on the one hand, nature, the essence of the object studied; on the other hand, we know only the external relations that are possible between it and other objects. In the first kind of knowledge, there is a possible question of a cognitio rei only when our intelligence apprehends an object, not simply under the form of external being, but in an intuition so immediate that we are able, by our senses and ideas, to penetrate its peculiar nature, and consequently, to know what ought to be, according to its internal and specific essence, the order of such a being. On the contrary, the other kind of scientific knowledge, the external, cognitio circa rem, does not penetrate to the essence of things, but consists mainly in a clear and precise apprehension of the conditions under which the object manifests itself to us, and under which, in consequence of its variable relations to other objects, jt is regularly transformed.[3]

Prior to Lotze's generation, philosophy had shaped scientific learning, leaving, at the same time, a large field open only to strict scientific treatment. In his person, science shapes philosophy, leaving, at the same time, a large field open only to strict philosophical treatment.[4] One is surprised that such a simple explanation should have escaped notice, and that a presentation of Lotze so fantastic—almost impertinent—as that of Ribot, for example, should have been perpetrated. Lotze's ability to see both sides of a problem, and his consequent sense for the limits of physiological psychology (which, in my humble judgment, remains completely justified still in essentials), provide the clue to his attitude. So, he really presents two kinds of psychology. One would investigate the factors, combinations and mechanism of consciousness; the other would consider the import of consciousness, and the end (if any) which it subserves in the universe. To understand-the latter it is necessary to master his very subtle cosmology ("Metaphysics," Bk. II.). The former is physiological psychology, and has been presented more particularly in Bks. II. and III. of the "Medical Psychology." Here Lotze writes as a scientific man, and the "conception of a psychophysical mechanism" suffices; that is, physical, chemical and physiological causality rules. Thus, he regards "physiology of the soul as an exposition of the mechanical conditions to which, according to our observation, the life of the soul is attached."[5] "The conception of a psychophysical mechanism can be stated as follows: As ideas, volitions and other mental states can not be compared with the quantitative and special properties of matter, but as, nevertheless, the latter seem to follow upon the former, it is evident that two essentially different, totally disparate, series of processes, one bodily and one mental, run parallel to each other. In the intensive quality of a mental process the extensive definiteness of the material process can never be found; but if the one is to call forth the other, the proportionality between them must be secured through a connection which appears to be extrinsic to both. There must exist general laws, which ensure that with a modification (a) of the mental substance a modification (b) of the bodily substance shall be connected, and it is only in consequence of this independent rule, and not through its own power and impulse, that a change in the soul produces a corresponding one in the body. . . . It is quite indifferent to medicine wherein the mysterious union of soul and body consists, as this is the constant event which lies equally at the bottom of all phenomena. But it is of the greatest interest to medicine to know what affections of the soul are connected in that mysterious manner with what affections of the body."[6] Accordingly, his phenomenal psychology was guided by competent knowledge of physics and physiology, the latter, as we must recall, being a subject which he actually professed. His speculative psychology, dealing with the mysterious union, falls within his philosophy.

The third book of the "Medical Psychology," which still conveys lessons to the physician, deals with subjects such as sleep, attention, emotion, the influence of the flow of consciousness upon secretion, nutrition, and instinct, and with abnormal psychology. The second book reviews the factors of self-consciousness, especially in the light of the relation between the physiological mechanism and the mind. It thus includes his most distinctive contribution to physiological psychology—the famous theory of "local signs." This is an integral part of his analysis of space-perception, one of the subtlest ever formulated. His latest presentation of it runs thus:

Let it be assumed that the soul once for all lies under the necessity of mentally presenting a certain manifold as in juxtaposition in space; How does it come to localize every individual impression at a definite place in the space intuited by it, in such manner that the entire image thus intuited is similar to the external object which acted on the eye?

Obviously, such a clue must lie in the impressions themselves. The simple quality of the sensation "green" or "red" does not, however, contain it; for every such color can in turn appear at every point in space, and on this account does not, of itself, require always to be referred to the one definite point.

We now remind ourselves, however, that the carefulness with which the regular position on the retina of the particular excitations is secured, can not be without a purpose. To be sure, an impression is not seen at a definite point on account of its being situated at such a point; but it may perhaps by means of this definite situation act on the soul otherwise than if it were elsewhere situated.

Accordingly we conceive of this in the following way: Every impression cf color "r"—for example, red—produces on all places of the retina, which it reaches, the same sensation of redness. In addition to this, however, it produces on each of these different places, a, b, c, a certain accessory impression, α, β, γ, which is independent of the nature of the color seen, and dependent merely on the nature of the place excited. This second local impression would therefore be associated with every impression of color "r," in such a manner that rα signifies a red that acts on the point a, rβ signifies the same red in case it acts on the point b. These associated accessory impressions would, accordingly, render for the soul the clue, by following which it transposes the same red, now to one, now to another spot, or simultaneously to different spots in the space intuited by it.

In order, however, that this may take place in a methodical way, these accessory impressions must be completely different from the main impressions, the colors, and must not disturb the latter. They must be, however, not merely of the same kind among themselves, but wholly definite members of a series or system of series; so that for every impression "r" there may be assigned, by the aid of this adjoined "local sign," not merely a particular, but a quite definite spot among all the rest of the impressions. The foregoing is the theory of "Local Signs."[7]

The best anatomical and physiological researches fail to reveal spatial order as inherent in sensation; and, even if this ignorance be due to the impossibility of following up the evolutionary regress, it is a real difficulty. Lotze therefore concluded that "localization in space belongs to the unconscious product of the soul's action through the mechanism of its internal states."[8] We gain a field of vision from an ensemble of local signs, and, as concerns tactile sense, the same thing happens, the functions of the corpuscles of touch being like those of the cones and rods of the retina in sight. As a result, our notion of the extended originates in a perception of qualitative differences, from which the mind, by its own power of transformation, constructs extensive relations. Later researches into the structure of the peripheral nerve terminations seem to confirm, rather than undermine, the hypothesis. That it is a typical example of the limitations of hypothesis Lotze acknowledged quite frankly. But he claimed, with justice, that it explained the actual phenomena better than any other theory. As a consequence, even if modified, it has been incorporated in physiological psychology, and, especially as regards vision and touch, must be reckoned with still.[9] To sum up—the point is this: Lotze held that every sensation, say, of color, was accompanied by an "accessory impression" of locality. The facts made it necessary to assume this "accessory impression." Now, just because it happens to be an assumption, it lies open to several interpretations. In other words, the principle of the hypothesis may stand, but opinions as to the way in which it may be read can differ widely. However this may be, more than any other psychologist, he has laid bare the numerous pitfalls surrounding the explanation of a psychological fact so obvious and common as space perception.

Nascent sciences present a certain family likeness in their life history. Commonly, they begin as special inquiries, somewhat off the traditional lines, in the science which bears close or closest affinity to the future discipline. Such movements continue lonely for a time, systematization being difficult or unattainable till many facts have been collected. To the point reached now we see this stage predominating in physiological psychology. Physics and anatomy, physiology and philosophy present special departures toward psychology, but a unification of the last still lacks. The final step must be associated always with the names of Gustav Theodor Fechner and Wilhelm Wundt (the latter more emphatically), who, building on the accumulations of their predecessors, at length brought the new science into formal shape.

Fechner (1801-87), like Lotze, studied medicine at Leipzig, where he became professor of physics in 1834. Like Lotze, too, he was an expert in philosophy. Both were "masters in the use of exact methods, yet at the same time with their whole souls devoted to the highest questions, and superior to their contemporaries in breadth of view as in the importance and range of their leading ideas—Fechner a dreamer and sober investigator by turns, Lotze with a gentle hand reconciling the antitheses in life and science."[10] In a fashion Fechner's psychology is more intimately connected with his philosophy than Lotze's, and his philosophico-psychological perspective offers points of strong contrast to Wundt's. Indeed, his definition of psychophysics—a term original with him—hints as much. "I understand by psychophysics an exact theory of the relations of soul and body, and, in a general way, of the physical world and the psychical world." Undoubtedly, the psychology may be disengaged from metaphysical entanglements, as Wundt said in his address on the occasion of the Fechner centenary.[11] But, after all, Fechner's panpsychism forms a motive force of his psychophysics, because, intellectually, he was a double personality.[12] His philosophical theory teaches a universal parallelism between the physical and the psychical. Or, as Nageli, the botanist, has it:

Sensation is clearly connected with the reflex actions of higher animals. We are obliged to concede it to the other animals also, and we have no grounds for denying it to plants and inorganic bodies. The sensation arouses in us a condition of comfort and discomfort. In general, the feeling of pleasure arises when the natural impulses are satisfied, the feeling of pain, when they are not satisfied. Since all material processes are composed of movements of molecules and elementary atoms, pleasure and pain must have its seat in these particles. Sensation is a property of the albuminous molecules; and if it belongs to these, we are obliged to concede it to the other substances also. If the molecules possess anything even remotely akin to sensation, they must have a feeling of comfort when they can obey the law of attraction or repulsion, the law of their own inclination or aversion; a feeling of discomfort, however, when they are compelled to make contrary movements. Thus the same thread runs through all material phenomena. The human mind is nothing but the highest development on our earth of the mental processes which universally animate and move nature.[13]

Fechner had worked out this fundamental theory ere he arrived at his psychological results. We find glimmerings of it so soon as 1835, in the attractive "Little Book on Life After Death," in the tract "On the Highest Good" (1846); enlarged views in "Nanna, or the Soullife of Plants" (1848); while the system appears full-fledged in "Zend-Avesta, or the Things of Heaven and the Hereafter" (1851); in 1861 he returned to it in his book, "On the Soul Question," occasioned by contemporary materialism, and in "The Three Motives and Grounds of Belief"; and in 1879 he reaffirmed and restated the position in the remarkable volume entitled "The Day View and the Night View." The essence of his teaching may be summed up in the thought that the material or external world is a half-truth, a concession to the sensuous, rather than an explanation of the psychical;

However complicated our brains may be, and however much we may feel inclined to attach to such a complexity the highest mental properties, the world is unspeakably more complex, since it is a complication of all the complications contained in it, the brains among them. Why not, therefore, attach still higher mental properties to this greater complexity? The form and structure of the heavens seem simple only when we consider the large masses and not their details and concatenation. The heavenly bodies are not crude homogeneous lumps; and the most diverse and complicated relations of light and gravity obtain between them. That, however, the plurality in the world is also grouped, comprehended, and organized into unity does not contradict the thought that it is also comprehended into a corresponding mental unity, but is in harmony with the same.[14]

Consequently, the physical symbolizes the psychical. They are two faces of a single existence. Human research may, therefore, deal with the one or the other, and attain, as it has attained, great success. But the real problem centers in the relation between the two. Of this, physiological psychology is the science. You can, accordingly, pursue it quâ science, but you must never forget the larger setting in which it finds itself.

Proceeding to the psychology, then, note at once that Fechner envisages the problem rather as a physicist than as a physiologist. So, he suffers from his limitations, but gains in precision. Soul and body being a single existence, it is practicable to investigate their mutual functioning and to state the results as laws of nature, which, in turn, are no more than assemblages of observations concerning phenomenal existence. Of course, a developed psychology would endeavor to extend this plan to the entire range of consciousness. Fechner, however, confines himself to a single fundamental point—the relation between stimulus and sensation as generalized in Weber's law; although, just as Lotze before him, he considers other questions in a most suggestive manner, such, notably, as the seat of the soul, sleep and reminiscence. In pursuance of his early conviction,' that soul and body are but opposite sides of an identical existence (conscious), he took it for granted that their reciprocal action would be proportional. But this was belief, not science. Weber's work led Fechner to test the hypothesis, that the increase of physiological excitation holds the key to psychological changes. And his interest was stimulated by the fact that, if this could be proved accurately, his philosophy would benefit by so much indubitable evidence. Consequently, he was moved to verify Weber's law by numerous experiments, chiefly of a physical sort. Sensations of pressure and muscular effort, detected by the use of weights; sensations of temperature, determined by cold and hot water; sensations of light, handled by the photometer; and sensations of sound, observed by reference to falling bodies, all tended to confirm the same general relation between stimulus and the psychological event. Given what Herbart called a "threshold of sensation," and having fixed this as a constant for each class of sensation, Fechner found it possible to infer, by strict induction, that the intensity of the sensation is equal to the proportion of the stimulus, multiplied by the logarithm of the excitation, divided by the threshold of stimulus. In other words, we can obtain a formula for the quantitative relation of physical and psychological events considered as magnitudes. This formula, which provides a means of measurement, declares that the sensations increase proportionally to the logarithm of the stimulus.[15] As a law, Fechner affirms dogmatically that it applies for internal (psychological) states and, within limits, reasons for which can be given, for external (physiological or physical) conditions. The result was obtained by three methods. (1) The Method of Differences which are Just Observable. This means that the operator finds, first, the least greater or the least smaller stimulus which can just be sensed as different by the subject; and then proceeds to add increments to this, or, inversely to subtract increments from it, till the intensity or diminution come into clear recognition. Divide the sum of the initial and the altered stimulus and you arrive at the differential of sensibility. (2) The Method of True (Eight) and False (Wrong) Cases. Here the operator applies two stimuli, which differ slightly, to the subject, and inquires whether the first is greater or smaller than the second. The replies are recorded; the ratio of true judgments to the total number of judgments gives the measure of sensibility, and varies directly with it. (3) The Method of Mean Errors—or of Probability of Error. Given a stimulus, the subject is asked to add another just equal to the datum. He deviates more or less; the probable error of the adjustment, in its deviation from the known mean, affords the direct measure of sensibility. The last, so far as an amateur can judge, would seem to be the most important, because the most accurate procedure. As has been said, the resultant generalization holds within limits, upper and lower.[16] But this is just what one anticipates in any law of nature. And there is another, much more pertinent, question. Does the law apply to the relation between sensation and neurosis, or merely to that between neurosis and excitation? If the former, it is psycho-physiological; if the latter, it is no more than physiological or, strictly, physical. Now this raises precisely the fundamental problem: Are sensations measurable? And this, in turn, seems to me to depend upon the possibility of differentiating between sensation and perception (the manner in which we experience sensation). So far as I catch the present drift, the central difficulty remains sub judice. On the other hand, if one be prepared to accept the theory that I call "organicism"—the analogue on the metaphysical side of activism on the ethical, which declares that our whole experience can only be interpreted as a single vast organism, in which every part bears a relation at once of means and end to every other, it follows plainly, in my judgment, that, if not Fechner's law, then some law (possibly not yet known, but necessary all the same) must be operative; and, further, that this law, in certain of its manifestations, is capable of discovery and verification by psycho-physiological methods. You see we must not demand finality from a new science in the first generation of its formal career. At this point the most pitiable errors have been made both by critics and by advocates. The critic who insists that physiological psychology has nothing to tell is in far too big a hurry to judge; and the advocate who urges that physiological psychology can tell everything forthwith deposes his own subject from its hard-earned place as a positive science. It is fair to add, as opposed to my own view, that the greatest American psychologist, Professor James,[17] states (1) that "Fechner's originality consists exclusively in the theoretic interpretation of Weber's law" (p. 545); (2) that "the entire superstructure which Fechner rears upon the facts is not only seen to be arbitrary and subjective, but in the highest degree improbable as well" (p. 547); and (3) that "Weber's law is probably purely physical" (p. 548). And he concludes, "the only amusing part of it is that Fechner's critics should always feel bound, after smiting his theories hip and thigh and leaving not a stick of them standing, to wind up by saying that nevertheless to him belongs the imperishable glory of first formulating them and thereby turning psychology into an exact science (!):

"And everybody praised the duke
Who this great fight did win."
"But what good came of it at last? "
Quoth little Peterkin.
"Why, that I can not tell," said he,
"But 'twas a famous victory" (p. 549).

All of which need not be taken with too many grimaces. For it merely means that physiological psychology remains in the "natural history" stage—it is still occupied mainly in the assemblage of facts. And no one would oppose it were it not that some foolish partisans, after the fashion of fools in all ages, go about to magnify their office. That psychology can never hope to be "exact" after the kind of physics, or even, mayhap, physiology, seems beyond doubt. Yet one attaches little, if any, weight to this remark. For, as physiology ceases to be physiology when it assimilates itself to physics or to chemistry, so psychology ceases to be psychology when it attempts to become physiology, just as sociology, masquerading in the guise of psychology, is no science, but simply a homeless bastard. Sceptical as the conclusion may seem, Fechner, nevertheless, needs no justification, as his work for esthetics proves abundantly.[18] For, in psychology, as in every other science, the investigator assumes the intelligibility of nature; and then, by an attack in detail, attempts to show that natural interrelations are as his conceptual conclusions anticipated they would be. And from this process no sphere of experience can be held exempt. Doubtless, the application is most difficult in psychology, because there abstraction from either body or mind leads to positive error. But, here, again, we are only saying that, despite all its laboratories and apparatus, psychology remains that new revelation—a philosophical science. And to my mind its first-rate importance grounds exactly in this very fact.

  1. Cf. "Formation de la notion d'espace" in Revue Philosophique, Vol. IV., pp. 345 ff.; appendix to Stumpf's "Ueber den psychologischen Ursprung d. Raumvorstellung" (1873); "Metaphysik," Bk. II., Chap. IV.; "Grundzuge d. Psychologie" (posthumous).
  2. Leben u. Lebenskraft, in Wagner's "Handwörterbuch," 1842.
  3. "Med. Psych.," Vol. I., p. 50.
  4. Cf. Rehnisch in Rev. Philos., XII., 321 ff.; Achelis in Vierteljahrs. f. wiss. Phil, 1882.
  5. "Kleine Schriften," II., p. 204.
  6. Ibid., I., pp. 193-97.
  7. "Grundzüge d. Psychologie" (1881); Eng. trans, (from ed. of 1884), pp. 51 ff.
  8. "Med. Psych.," Bk. II., Sect. 294.
  9. Cf. "Elements of Physiological Psychology," Ladd, pp. 396 ff.; "Principles of Psychology," James, Vol. II., pp. 157 f.; "German Psychology of To-day," Ribot, p. 95 (Eng. trans.).
  10. "History of Modern Philosophy," Falckenberg, pp. 601-2 (Eng. trans.).
  11. Cf. "Gustav Theodor Fechner," K. Lasswitz, p. 91.
  12. Cf. ibid., p. 154.
  13. Cf. "Die mechanische-physiologische Theorie d. Abstammungslehre" (1884).
  14. "Ideen zu einer Schöpfungsgeschichte," p. 106.
  15. Cf. "German Psychology of To-day," Ribot, pp. 138 f. (Eng. trans.); "Outlines of Psychology," Külpe, pp. 164 f.; Ward in Mind, Vol. I. (old series), pp. 452 ff.; or in any standard psychology, e. g., James or Wundt or Ladd.
  16. Ribot, q. s., p. 168; Helmholtz, "Physiol. Optik," pp. 314 f.; "Hereditary Genius," Galton; and, for a very destructive view, "Introduction to Psychological Theory," Bowne, pp. 49 ff. See also refs. under Weber's law above.
  17. Cf. "Principles of Psychology," Vol. I., Chap. XIII.
  18. Cf. "Fechner," Lasswitz, p. 101.