'PERCEPTION-TIME.'
Project Gutenberg EPUB3 edition
James, William
The time which the perceptive process occupies has been inquired into by various experimenters. Some call it perception-time, some choice-time, some discrimination-time. The results have been already given in Chapter XIII (vol. I, p. 523 ff.), to which the reader is consequently referred.
Dr. Romanes gives an interesting variation of these time-measurements. He found[138]
"an astonishing difference between different individuals with respect to the rate at which they are able to read. Of course reading implies enormously intricate processes of perception both of the sensuous and of the intellectual order; but if we choose for these observations persons who have been accustomed to read much, we may consider that they are all very much on a par with respect to the amount of practice which they have had, so that the differences in their rates of reading may fairly be attributed to real differences in their rates of forming complex perceptions in rapid succession, and not to any merely accidental differences arising from greater or less facility acquired by special practice.
"My experiments consisted in marking a brief printed paragraph in a book which had never been read by any of the persons to whom it was to be presented. The paragraph, which contained simple statements of simple facts, was marked on the margin with pencil. The book was then placed before the reader open, the page, however, being covered with a sheet of paper. Having pointed out to the reader upon this sheet of paper what part of the underlying page the marked paragraph occupied, I suddenly removed the sheet of paper with one hand, while I started a chronograph with the other. Twenty seconds being allowed for reading the paragraph (ten lines octavo), as soon as the time was up I again suddenly placed the sheet of paper over the printed page, passed the book on to the next reader, and repeated the experiment as before. Meanwhile, the first reader, the moment after the book had been removed, wrote down all that he or she could remember having read. And so on with all the other readers.
"Now the results of a number of experiments conducted on this method were to show, as I have said, astonishing differences in the maximum rate of reading which is possible to different individuals, all of whom have been accustomed to extensive reading. That is to say, the difference may amount to 4 to 1; or, otherwise stated, in a given time one individual may be able to read four times as much as another. Moreover, it appeared that there was no relationship between slowness of reading and power of assimilation; on the contrary, when all the efforts are directed to assimilating as much as possible in a given time, the rapid readers (as shown by their written notes) usually give a better account of the portions of the paragraph which have been compassed by the slow readers than the latter are able to give; and the most rapid reader I have found is also the best at assimilating. I should further say that there is no relationship between rapidity of perception as thus tested and intellectual activity as tested by the general results of intellectual work; for I have tried the experiment with several highly distinguished men in science and literature, most of whom I found to be slow readers."[139]
Source notes
[83] The word Perception, however, has been variously used. For historical notices, see Hamilton's Lectures on Metaphysics, ii. 96. For Hamilton perception is 'the consciousness of external objects' (ib. 28). Spencer defines it oddly enough as "a discerning of the relation or relations between states of consciousness partly presentative and partly representative; which states of consciousness must be themselves known to the extent involved in the knowledge of their relations" (Psychol., § 355).
[84] Analysis, i. 97.
[85] Theory of Vision, 51.
[86] The educative process is particularly obvious in the case of the ear, for all sudden sounds seem alarming to babies. The familiar noises of house and street keep them in constant trepidation until such time as they have either learned the objects which emit them, or have become blunted to them by frequent experience of their innocuity.
[87] Outlines, p. 153.
[88] Cf. Helmholtz, Optik, pp. 433, 723, 728, 772; and Spencer, Psychology, vol. ii. p. 249, note.
[89] The more or less geometrically regular phantasms which are produced by pressure on the eyeballs, congestion of the head, inhalation of anæsthetics, etc., might again be cited to prove that faint and vague excitements of sense-organs are transformed into figured objects by the brain, only the facts are not quite clearly interpretable; and the figuring may possibly be due to some retinal peculiarity, as yet unexplored. Beautiful patterns, which would do for wall-papers, succeed each other when the eyeballs are long pressed. Goethe's account of his own phantasm of a flower is well known. It came in the middle of his visual field whenever he closed his eyes and depressed his head, "unfolding itself and developing from its interior new flowers, formed of colored or sometimes green leaves, not natural but of fantastic forms, and symmetrical as the rosettes of sculptors," etc. (quoted in Müller's Physiology, Baly's tr., p. 1397). The fortification- and zigzag-patterns, which are well-known appearances in the field of view in certain functional disorders, have characteristics (steadiness, coerciveness, blotting out of other objects) suggestive of a retinal origin—this is why the entire class of phenomena treated of in this note seem to me still doubtfully connected with the cerebral factor in perception of which the text treats.—I copy from Taine's book on Intelligence (vol. i. p. 61) the translation of an interesting observation by Prof. M. Lazarus, in which the same effect of an after-image is seen.
Lazarus himself proposes the name of 'visionary illusions' for such modifications of ideal pictures by peripheral stimulations (Lehre von den Sinnestäuschungen, 1867, p. 19). "I was on the Kaltbad terrace at Rigi, on a very clear afternoon, and attempting to make out the Waldbruder, a rock which stands out from the midst of the gigantic wall of mountains surrounding it, on whose summits we see like a crown the glaciers of Titlis, Uri-Rothsdock, etc. I was looking alternately with the naked eye and with a spy-glass; but could not distinguish it with the naked eye. For the space of six to ten minutes I had gazed steadfastly upon the mountains, whose color varied according to their several altitudes or declivities between violet, brown, and dark green, and I had fatigued myself to no purpose, when I ceased looking and turned away. At that moment I saw before me (I cannot recollect whether my eyes were shut or open) the figure of an absent friend, like a corpse.... I asked myself at once how I had come to think of my absent friend.—In a few seconds I regained the thread of my thoughts, which my looking for the Waldbruder had interrupted, and readily found that the idea of my friend had by a very simple necessity introduced itself among them. My recollecting him was thus naturally accounted for.—But in addition to this, he had appeared as a corpse. How was this?—At this moment, whether through fatigue or in order to think, I closed my eyes, and found at once the whole field of sight, over a considerable extent, covered with the same corpse-like hue, a greenish-yellow gray.
I thought at once that I had here the principle of the desired explanation, and attempted to recall to memory the forms of other persons. And, in fact, these forms too appeared like corpses; standing or sitting, as I wished, all had a corpse-like tint. The persons whom I wished to see did not all appear to me as sensible phantoms; and again, when my eyes were open. I did not see phantoms, or at all events only saw them faintly, of no determined color.—I then inquired how it was that phantoms of persons were affected by and colored like the visual field surrounding them, how their outlines were traced, and if their faces and clothes were of the same color. But it was then too late, or perhaps the influence of reflection and examination had been too powerful. All grew suddenly pale, and the subjective phenomenon, which might have lasted some minutes longer, had disappeared.—It is plain that here an inward reminiscence, arising in accordance with the laws of association, had combined with an optical after-image. The excessive excitation of the periphery of the optic nerve, I mean the long-continued preceding sensation of my eyes when contemplating the color of the mountain, had indirectly provoked a subjective and durable sensation, that of the complementary color; and my reminiscence, incorporating itself with this subjective sensation, became the corpse-like phantom I have described."
[90] Cf. Th. Reid's Intellectual Powers, essay ii. chap. xxii, and A. Binet, in Mind, ix. 206. M. Binet points out the fact that what is fallaciously inferred is always an object of some other sense than the 'this.' 'Optical illusions' are generally errors of touch and muscular sensibility, and the fallaciously perceived object and the experiences which correct it are both tactile in these cases.
[91] The converse illusion is hard to bring about. The points a and b, being normally in contact, mean to us the same space, and hence it might be supposed that when simultaneously touched, as by a pair of callipers, we should feel but one object, whilst us a matter of fact we feel two. It should be remarked in explanation of this that an object placed between the two fingers in their normal uncrossed position always awakens the sense of two contacts. When the fingers are pressed together we feel one object to be between them. And when the fingers are crossed, and their corresponding points a and b simultaneously pressed, we do get something like the illusion of singleness—that is, we get a very doubtful doubleness.
[92] Purkinje, Mach, and Breuer are the authors to whom we mainly owe the explanation of the feeling of vertigo. I have found (American Journal of Otology, Oct. 1882) that in deaf-mutes (whose semi-circular canals or entire auditory nerves must often be disorganized) there very frequently exists no susceptibility to giddiness or whirling.
[93] The involuntary continuance of the eye's motions is not the only cause of the false perception in these cases. There is also a true negative after-image of the original retinal movement-sensations, as we shall see in Chapter XX.
[94] We never, so far as I know, get the converse illusion at a railroad station and believe the other train to move when it is still.
[95] Helmholtz: Physiol. Optik, 365.
[96] Cf. Berkeley's Theory of Vision, §§ 67-79; Helmholtz: Physiologische Optik, pp. 630-1; Lechalas in Revue Philosophique, xxvi. 49.
[97] Physiol. Optik, p. 602.
[98] It seems likely that the strains in the recti muscles have something to do with the vacillating judgment in these atropin cases. The internal recti contract whenever we accommodate. They squint and produce double vision when the innervation for accommodation is excessive. To see singly, when straining the atropinized accommodation, the contraction of our internal recti must be neutralized by a correspondingly excessive contraction of the external recti. But this is a sign of the object's recession, etc.
[99] American Journal of Psychology, i. 101 ff.
[100] Romanes, Mental Evolution in Animals, p. 324.
[101] M. Lazarus: Das Leben d. Seele, ii (1857), p. 32. In the ordinary hearing of speech half the words we seem to hear are supplied out of our own head. A language with which we are perfectly familiar is understood, even when spoken in low tones and far off. An unfamiliar language is unintelligible under these conditions. If we do not get a very good seat at a foreign theatre, we fail to follow the dialogue; and what gives trouble to most of us when abroad is not only that the natives speak so fast, but that they speak so indistinctly and so low. The verbal objects for interpreting the sounds by are not alert and ready made in our minds, as they are in our familiar mother-tongue, and do not start up at so faint a cue.
[102] G. H. Meyer, Untersuchungen, etc., pp. 242-8.
[103] Helmholtz, P. O. 438. The question will soon come before us again in the chapter on the Perception of Space.
[104] C. F. Taylor, Sensation and Pain, p. 37 (N. Y., 1882).
[105] Examen Critique de la Loi Psychophysique (1883), p. 61.
[106] Compare A. W Volkmann's essay 'Ueber Ursprüngliches und Erworbenes in den Raumanschauungen,' on p. 139 of his Untersuchungen im Gebiete der Optik; and Chapter xiii of Hering's contribution to Hermann's Handbuch der Physiologie, vol. iii.
[107] In the Proceedings of the American Society for Psychical Research, pp. 253-4, I have tried to account for some of the variations in this consciousness. Out of 140 persons whom I found to feel their lost foot, some did so dubiously. "Either they only feel it occasionally, or only when it pains them, or only when they try to move it; or they only feel it when they 'think a good deal about it' and make an effort to conjure it up. When they 'grow inattentive,' the feeling 'flies back' or 'jumps back,' to the stump. Every degree of consciousness, from complete and permanent hallucination down to something hardly distinguishable from ordinary fancy, seems represented in the sense of the missing extremity which these patients say they have. Indeed I have seldom seen a more plausible lot of evidence for the view that imagination and sensation are but differences of vividness in an identical process than these confessions, taking them altogether, contain. Many patients say they can hardly tell whether they feel or fancy the limb."
[108] Pflüger's Archiv, xxxvii. 1.
[109] Not all patients have this additional illusion.
[110] I ought to say that in almost all cases the volition is followed by actual contraction of muscles in the stump.
[111] Cf. Herbart, Psychol. als. Wissenschaft, § 125.
[112] Compare the historical reviews by K. Lange: Ueber Apperception (Plauen, 1879), pp. 12-14; by Staude in Wundt's Philosophische Studien, i. 149; and by Marty in Vierteljsch. f. wiss. Phil., x. 347 ff.
[113] Problems, vol. i. p. 118 ff.
[114] See his Einleitung in die Psychologie u. Sprachwissenschaft (1881) p. 166 ff.
[115] One of my colleagues, asking himself the question after reading the anecdote, tells me that he replied 'Harvard College,' the faculty of that body having voted, a few days previously, to keep back the degrees of members of the graduating class who might be disorderly on class-day night. W. J.