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If we put these results into the form of propositions, we find:
1. That when the objects are similar surfaces, seen under similar conditions, the chances of the recurrence and persistence of their images are, on the whole, practically equal.
2. That surfaces bounded by complicated outlines have an advantage in ideation, other things equal, over surfaces bounded by simple outlines.
3. That as between two objects of unequal area—color, form, and other conditions being the same—the larger object has the advantage in the ideational rivalry.
4. That the image of a white object has a like advantage over the image of a gray object.
5. That broken or complex lines have in ideation an advantage over straight or simple lines.
6. That an object with varied content, other conditions remaining the same, has an advantage over an object with homogeneous surface.
7 and 8. That an increase of the time during which the attention is given to an object increases the chances for the recurrence of its image or idea.
9. That of two objects to which attention is directed in succession, the object last seen has a distinct advantage in the course of ideation following close on the perception of the objects.
10. That lines of similar appearance and equal length, one of which is vertical and the other horizontal, have, like surfaces of similar appearance and form and equal dimensions, practically equal chances of recurrence and survival in ideation, the slight difference in their chances being in favor of the vertical line.
11. That as between two figures of similar form and equal dimensions, one of which has a filled homogeneous content and the other is a mere outline figure, the latter has a marked advantage in the course of ideation.
12. That of two linear and symmetrical figures, of which one is an outline figure with continuous boundary, and the other consists of the same linear elements, similarly disposed, as the first, but has its lines disconnected so that it has no continuous boundary, the latter figure has the advantage in ideation.
13. That if, with material similar to that described in paragraph 12, the disconnected lines are arranged so as to be vertical and equidistant, the advantage in ideation still remains with the disconnected lines, but is much reduced.
14. That if one of two figures, of similar appearance and form and of equal dimensions, is kept in motion while it is exposed to view, and the other is left at rest, the image of the moving object is the more persistent.
15. That, under like conditions, colored objects are more persistent in ideation than gray objects.
16. That lines and sharp angles, as compared with broad surfaces, have a strong directive force in the determination of the attention to their images or ideas; that this directive force is strongest in the case of very acute angles, the attention being carried forward in the direction indicated by the apex of the angle; but that uncompleted lines, especially when two such lines are directed towards each other, have a similar and not much inferior force in the control of the course of ideation.
If we should seek now to generalize these experimental results, they would take some such form as the following:
Abstraction made of all volitional aims and all aesthetic or affective bias, the tendency of an object to recur and persist in idea depends (within the limits imposed by the conditions of these experiments) upon the extent of its surface, the complexity of its form, the diversity of its contents, the length and recency of the time during which it occupies the attention, the definiteness of the direction which it imparts to the attention (as in the case of angles and lines), its state of motion or of rest, and, finally, its brightness and its color.
These conditions, however, are for the most part but conditions which determine the energy, diversity, complexity and definiteness of the active processes involved in the bestowal of attention upon its object, and the experiments show that such active processes are as essential in ideation as in perception. The stability of an image, or internal sensation, thus depends on the activity of its motor accompaniments or conditions. And as the presence of an image to the exclusion of a rival, which but for the effect of these motor advantages would have as strong a claim as itself to the occupation of consciousness (cf. Series I., X.), may be treated as a case of inhibition, the greater the relative persistence of an image or idea the greater we may say is the 'force' with which it inhibits its rival. Exclusive possession of the field involves, to the extent to which such possession is made good, actual exclusion of the rival; and exclusion is inhibition. Our generalization, accordingly, may take the following form:—
The inhibitory effect of an idea, apart from volitional or emotional bias, depends upon the energy, diversity, complexity and definiteness of the motor conditions of the idea.
* * * * *
CONTROL OF THE MEMORY IMAGE.
BY CHARLES S. MOORE.
Since Gallon's classic investigation in the field of mental imagery several similar investigations have been pursued in the same direction, chiefly, however, for the purpose of discovering and classifying types of imagination.
Little has been done in the line of developing and studying the problems of the memory image proper, and still less, in fact almost nothing, is to be found bearing on the control of the visual memory image. The general fact of this control has been presented, with greater or less detail, based upon returns from questionaries. Gallon himself, for example, having referred to instances in which the control was lacking, goes on to say[1]: "Others have complete mastery over their mental images. They can call up the figure of a friend and make it sit on a chair or stand up at will; they can make it turn round and attitudinize in any way, as by mounting it on a bicycle or compelling it to perform gymnastic feats on a trapeze. They are able to build up elaborate structures bit by bit in their mind's eye and add, substract or alter at will and at leisure."
[1] Gallon, Francis: 'Inquiries into Human Faculty and its Development,' London, 1883, p. 109.
More recent writers classify the students, or other persons examined, according to these persons' own statements with regard to the nature and degree of control over the mental images which they consider themselves to possess. An article by Bentley[2] is the only study of a specific problem of the memory image. After a glance at the literature with reference to methods pursued in the investigation of problems of memory in general, Bentley outlines 'a static and genetic account' of the memory image in particular, and presents details of experiments 'carried on for the special investigation of the visual memory image and its fidelity to an original presentation.'
[2] Bentley, I.M.: 'The Memory Image and its Qualitative Fidelity,' Am. Journ. of Psychol., 1899, XI., pp. 1-48.
Of the many memory problems as yet unattacked, that of the control of the mental image is one of the most interesting. The visual image obviously offers itself as the most accessible and the experiments described in this report were undertaken with the purpose of finding out something about the processes by which control of this image is secured and maintained. The report naturally has two aspects, one numerical and the other subjective, presenting the statements of the subjects as to their inner experiences.
The term 'suppression' is used as a convenient one to cover the enforced disappearance of the designated image, whether it be directly forced out of consciousness (a true suppression) or indirectly caused to disappear through neglect, or limitation of the attention to the other image which is to be retained.
As this was an investigation of the control of memory images, the presence of these images under conditions most favorable to their vividness and distinctness was desirable. An immediate mental recall at the end of five seconds of visual stimulation, under favorable though not unusual conditions of light, position and distance, seemed most likely to secure this desideratum. Experimentation showed that five minutes was, on the whole, a suitable period in which to secure the information needed without developing a fatigue in the subject which would vitiate the results.
The experiments made in the visual field were restricted to visual memory images which were called up by the subject during the five minutes succeeding a five seconds' presentation of one or two objects. The subject sat, with his eyes closed, about four feet from a wall or screen, before which the object was placed. At a signal the eyes were opened, and at a second signal five seconds later they were closed. If an after-image appeared the subject reported its disappearance, and then called up the image of the object just presented, and reported as to its clearness, vividness, persistency and whatever phenomena arose; and when directed he sought to modify the image in various ways to be described later.
There were six subjects in experiments conducted during the winter of 1900-1901, and six (five being new ones) in experiments of the fall of 1901. They were all good visualizers, though they differed in the readiness with which they visualized respectively form or color.
The experiments of the first few weeks were designed to establish the fact of control by the subjects over a single visual memory image as to its position, size, outline, color, movement and presence. In general it was established that a considerable degree of control in these particulars existed in these subjects.
Later, two objects were presented at a time, and were such small articles as a glass ball, a book, a silk purse, an eye-glass case, an iron hook, and so forth. Still later, colored squares, triangles, or discs were used exclusively.
The investigation followed these lines: I. Movements of a single image; II. Changes of color of a single image; III. Movements of two images in the same and in different directions; IV. Suppression of one of two images; V. Movements of a single image, the object having been moved during the exposure.
I. MOVEMENTS OF A SINGLE IMAGE.
The first table gives the time in seconds taken to move voluntarily a single image (of a colored square or disc) to the right, left, up or down, and in each case to restore it to its original position. There were thirty movements of each kind for each of the six subjects, making one hundred and eighty for each direction and also for each return, the total of all movements being fourteen hundred and forty. The distance to which the subjects moved the images was not fixed, but was in most cases about twelve inches. The time was taken with a stop-watch, and includes the time between the word of command, 'right,' etc., of the director and the verbal report 'now' of the subject. It includes, therefore, for each movement two reaction times. The subject reported 'now' the instant the color reached, or appeared at, the designated place, not waiting for the completion of the shape which usually followed. Two of the subjects (H. and K.) took much longer than the other four, their combined average time being almost exactly four times the combined average time of the other four.
TABLE I.
MOVEMENTS OF A SINGLE IMAGE.
30 Movements of Each Kind for Each Subject Average Time in Seconds.
To To Subjects Right Return Left Return Up Return Down Return Averages B. 1.30 1.07 1.06 1.11 1.13 0.58 0.73 0.46 0.45 0.55
G. 1.44 1.15 0.99 0.82 1.10 0.92 0.89 0.76 0.57 0.78
H. 7.12 6.42 5.96 5.85 6.34 4.51 4.41 4.36 4.40 4.42
I. 1.28 1.34 1.62 1.47 1.43 0.67 0.62 0.86 0.72 0.72
J. 1.71 1.42 1.40 1.14 1.50 1.34 1.53 0.77 0.74 1.09
K. 4.81 4.64 3.29 3.28 4.01 2.40 2.71 1.91 1.56 2.14
Averages 2.95 2.67 2.39 2.23 2.59 1.72 1.82 1.52 1.41 1.62
NUMERICAL.
The general averages for the different movements show that movement to the right was hardest, to the left next; while movement downward was the easiest. A marked exception is seen in I., for whom the upward movement was the hardest and movement to the right was the easiest. J. found movement to the left hardest. For the return movements, the general averages show that the return from the left is the hardest, from the right next; while from below is the easiest. Here again I. found the return from above the hardest and from below the next hardest; while from the left was the easiest.
Arranging the subjects in the order of the average time, taken for all the movements, including the returns to the original position, we have
H. 5.35 average time out and back. K. 3.07 " " " " " J. 1.29 " " " " " I. 1.07 " " " " " G. .94 " " " " " B. .84 " " " " "
SUBJECTIVE.
All the six subjects whose time records appear in Table I. and also four others whose time was not recorded reported eye movements, or a tendency to eye movement. A. and K. reported that when the image was dim there was accommodation as for long vision and when the image was vivid there was accommodation as for near vision. B. ideated the new position and the eye movement occurred automatically. G. reported a contraction of the scalp muscles and a tendency to cast the eyes up and locate the image at the back of the head inside; this was an inveterate habit. He reported also accommodation for the different distances of the image and an after-feeling of strain in the head. H. reported a strong tendency in the eyes to return to the center, i.e., the original position, and to carry the image back there. All the subjects frequently reported a sense of relief in the eye muscles when the command to return the image to the center was given—also, a tension in the forehead in the upward movement which was accentuated (with H.) when there was headache. J. reported, 'always eye strain,' and noticed that the eyes usually turned as far as the new position, but sometimes stopped short of it. K. reported first an eye movement, then an ideation of the image in the new position. E. and H. turned the head to right and left for movements of the image in those directions. A., B., E. and F. believed that they could inhibit the eye movement. Subjects were at times unconscious of eye movements. H. articulated the names of the colors of the image and found that it aided the movement of the image to say to himself, for example: "Don't you see that blue square there?"
All but J. reported a loss in vividness and also, though to a less degree, in distinctness whenever the image was moved away from the center. J. found no difference. H. reported that details of the object which were reproduced in the image when at the center were not discernible in the image in other positions, also that at the left the image was more vivid than at the right. B.'s memory image of a watch, three minutes after it was called up, was still so clear that he read from it the time. E., who was an experienced photographer, had no difficulty in recalling outline, light and shade, but had difficulty in reproducing color. I. frequently lost the form in making the required improvements.
Under manipulation the memory image usually retained its distinctness and vividness with no loss or with but slight loss when in its original position, to the end of the five minutes of the experiment. The image, also, seldom disappeared except for the momentary disappearances in passing from one position to another, which are referred to later. Under passive observation of the memory image disappearances, though of short duration, were frequent and there was a noticeable fading away of color and loss of outline.
The memory image almost without exception, when first recalled, was located in the direction and at the distance of the object presented.
In moving from the center to right and left the image remained in the same plane with a few exceptions; in moving up and down it moved on an arc whose center was at the eye. This was especially true of the downward motion, which was almost always to a greater distance than any of the other motions.
C., D., F. and H. felt the need of a support for the image in any except the central position. This was true especially of the position above the center, but was entirely overcome by practice by C., F. and H., and partially by D. In movements where time was to be recorded, the distance was from six to eighteen inches, but the image could be carried by all the eleven subjects to any part of the room or beyond the room. Usually the method followed was to fix the attention on the suggested position and then the image appeared there, sometimes complete at the outset, but usually in part at first, then developing instantly to completion. When the subject was requested to trace the image in transitu, this could usually be accomplished, but the time was much longer. Frequently, in such a case, the image was lost during the last third or fifth of its journey. J. "felt conscious of a something that went in the suggested direction but did not develop details out of this material; had to await development of the image at the new locality." "At times forced this development out of the vague something that seemed to go over." G. had 'no feeling of transition in space.' K. did not perceive the image in transitu. I. perceived the image in transitu when the movement was away from the center but when the image was to return to the center its passage was too quick to be followed; 'it came out at the center.'
J. noticed that in moving from the center the image took a curved path towards himself, and that the position to which the image moved always seemed further away than the position from which it came, but the new position seemed to be readjusted when the next movement occurred.
The return to the center seemed easier to all the subjects except G., who was conscious of no difference between the movements with respect to ease. Several described the return to the center as like the return of a small ball snapped back by a stretched elastic cord.
With D. a suggestion of weight in the perception of the object was a hindrance to moving its memory image. Also the image of a short piece of brass tubing persisted in rolling off the table and along the floor and could not be held stationary. Other objects rotated rapidly, and much effort was needed to 'slow down' the rotation and to bring the objects to rest and keep them at rest.
II. CHANGES OF COLOR OF A SINGLE IMAGE.
Tables II. and III. show the results of experiments in changing the color of a single image. This was usually a square, sometimes a disc. The time of optical perception was five seconds. After the disappearance of after-images, if there were any, eighteen to twenty-four changes were made in the color of the memory image, occupying from four and a half to six minutes.
The colors were saturated blue, green, yellow and red, and each one was changed into each of the other colors and then restored. The order of change was varied to avoid uniformity of succession. The four colors were shown to the subjects each day before the experiments began, to establish a standard. The time was taken with a stop-watch, and includes the time between the director's word of command, 'green,' etc., and the subject's report, 'now,' or 'green,' etc. It includes, therefore, two reaction times. The subject reported 'now' the instant he secured the desired color, not waiting for the completion of the shape that usually followed.
TABLE II.
CHANGES OF COLOR. SINGLE IMAGE. 72 CHANGES OF EACH COLOR.
[Label 1: Subject.] [Label 2: To Green.] [Label 3: Return to Blue.] [Label 4: To Yellow.] [Label 5: Return to Blue.] [Label 6: To Red.] [Label 7: Return to Blue.] [Label 8: To Blue.] [Label 9: Return to Green.] [Label 10: To Yellow.] [Label 11: Return to Green.] [Label 12: To Red] [Label 13: Return to Green.]
From Blue. From Green. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
B. 1.72 0.50 1.66 0.38 1.81 0.50 1.23 0.56 1.10 0.65 1.33 0.56 G. 1.15 0.60 1.10 0.79 0.89 0.65 1.75 0.87 1.04 0.75 1.35 0.71 H. 4.67 4.25 4.87 4.06 4.81 3.83 5.27 4.50 5.81 4.89 5.37 4.94 I. 2.27 1.25 1.77 1.19 1.83 1.25 2.15 0.93 1.71 1.04 1.92 1.15 J. 1.38 0.81 1.29 0.94 1.29 0.95 1.65 1.08 1.15 0.77 1.60 0.81 K. 2.35 1.71 1.96 1.66 2.10 1.19 2.25 1.25 2.17 1.73 2.44 1.27
Av. 2.26 1.52 2.11 1.50 2.15 1.39 2.41 1.53 2.15 1.65 2.34 1.57
[Label 1: Subject.] [Label 2: To Blue.] [Label 3: Return to Yellow.] [Label 4: To Green.] [Label 5: Return to Yellow.] [Label 6: To Red.] [Label 7: Return to Yellow.] [Label 8: To Blue.] [Label 9: Return to Red.] [Label 10: To Green.] [Label 11: Return to Red.] [Label 12: To Yellow.] [Label 13: Return to Red.]
From Yellow. From Red. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
B. 1.79 1.06 1.35 0.87 1.89 1.10 1.54 0.58 1.71 0.62 1.31 0.71 G. 1.50 1.10 1.48 0.87 1.31 0.88 1.33 0.92 1.35 0.91 0.77 0.58 H. 5.02 4.54 5.73 3.91 6.15 4.17 6.35 3.91 5.89 4.69 5.54 4.37 I. 2.29 1.31 2.54 1.19 2.29 1.27 2.85 1.10 2.50 1.21 1.65 1.31 J. 1.35 0.98 1.35 0.65 1.27 0.88 1.42 1.04 1.31 1.02 1.25 0.85 K. 3.02 1.52 3.21 2.04 2.23 1.79 2.54 1.56 2.66 1.60 2.88 1.81
Av. 2.49 1.76 2.61 1.59 2.52 1.68 2.67 1.51 2.57 1.68 2.23 1.62
TABLE III.
CHANGES TO THE FOUR COLORS.
Average time in seconds. 72 changes from and 72 changes to each color.
[Label 1: To Blue.] [Label 2: Return from Blue.] [Label 3: To Green.] [Label 4: Return from Green.] [Label 5: To Yellow.] [Label 6: Return from Yellow.] [Label 7: To Red.] [Label 8: Return from Red.]
[1] [2] [3] [4] [5] [6] [7] [8] From blue, 2.26 1.52 2.11 1.50 2.12 1.39 " green, 2.38 1.53 2.16 1.64 2.33 1.57 " yellow, 2.49 1.75 2.61 1.59 2.52 1.68 " red, 2.67 1.52 2.58 1.68 2.27 1.62
Average, 2.52 1.60 2.48 1.59 2.17 1.58 2.33 1.55
Changes from a presented color. Returns to a presented color. 216 movements. 216 movements.
From presented yellow, 2.52 To presented yellow, 1.67 " " red, 2.49 " " red, 1.61 " " green, 2.29 " " green, 1.58 " " blue, 2.16 " " blue, 1.47
Average, 2.37 Average, 1.58
Changes to a color from Returns from a color to a presented color. a presented color. 216 movements. 216 movements.
To blue, 2.52 From blue, 1.60 " green, 2.48 " green, 1.59 " red, 2.33 " yellow, 1.58 " yellow, 2.17 " red, 1.55
Average, 2.37 Average, 1.58
The six subjects fall into two groups—three, H., I., and K., taking longer than the other three. As in the previous experiment H. was markedly longer than any of the others.
There were seventeen hundred and twenty-eight changes in all, including returns to the original color. There were two hundred and sixteen changes from each of the four colors as presented, to each of the other three and, of course, the same number of returns to the presented color.
The change to blue from the other presented colors was the most difficult and the change to yellow was the easiest.
The averages (216 exp. each) are,
Sec. To blue, 2.55 " green, 2.48 " red, 2.33 " yellow, 2.17
The returns to the presented colors did not differ greatly from each other, the averages (216 exp. each) being:
Sec. From blue, 1.603 " green, 1.597 " yellow, 1.589 " red, 1.549
From red appears to be the easiest change, and from blue the hardest.
The getting away from a presented blue was the easiest and from a presented yellow the most difficult, as seen by these averages (216 exp. each):
Sec. From yellow, 2.54 " red, 2.49 " green, 2.29 " blue, 2.16
The returns to the presented colors show that it was hardest to get back to the presented yellow, easiest to get back to the presented blue, the averages (216 exp. each), being:
Sec. To yellow, 1.67 " red, 1.61 " green, 1.58 " blue, 1.47
The facts as to blue and yellow shown by these four tables of averages may be expressed also in this way:
If a blue square was shown, it was easier to change the blue memory image into the other colors, and also easier to get back the blue memory image after such changes, than if any other of the three colors was presented.
If another color than blue was shown it was harder to change the memory image of that color to blue than to any of the other colors, and also harder to get back to the memory image of that color from blue than from any of the other three colors.
If a yellow square was shown, it was harder to change the yellow memory image into the other colors, and also harder to get back the yellow memory image after such changes than if any other of the three colors was presented.
If another color than yellow was shown, it was easier to change the memory image of that color to yellow than to any of the three other colors, and also easier to get back to the memory image of that color from the yellow than from any of the other three colors except red.
If we combine all the changes into a color (both changes from another presented color and returns to this color previously presented) we find that changes to green are hardest, to yellow easiest. The averages (for 432 exp. each) are,
Sec. To green, 2.03 " blue, 1.99 " red, 1.97 " yellow, 1.92
The changes away from a color (both from this color previously presented and from this color to the other previously presented colors) show that it was hardest to get away from yellow, easiest to get away from blue, the averages (for 432 exp. each) being:
Sec. From yellow, 2.06 " red, 2.02 " green, 1.94 " blue, 1.88
As for the subjects, all six found yellow the easiest to change into, one finding red equally easy.
SUBJECTIVE.
For seven of the subjects, mental repetition of the name of the color (usually accompanied by articulatory movements) tended to bring up the color, and one other subject occasionally used this method of bringing about a change that was difficult. With D. the color did not come at repetition of the name. G. was assisted by auditory recall of the name. Nine subjects reported a feeling of strain, usually in the eyes as of focusing, occurring especially when there seemed a difficulty in producing the desired change. The tension attended almost exclusively changes of the presented color, not restorations of that color. For D. this strain was considerable, for G. there was also an after-feeling of strain in the head. For G. the image was clearest when the feeling of strain was least, and J. secured the promptest and clearest results when he could most nearly rid himself of anxiety as to the result. K. in one instance (a change from green to yellow) became conscious of the setting of his jaws and motions of feet and body in aid of his attempt. H. frequently had the feeling of physical fatigue.
In most cases the restoration of the presented color was as a complete square, triangle, etc. In changes from the presented color the new color appeared at a corner, or edge, or as a patch at the center. With E. the "color flashed over the whole field and then had to be restricted to the figure." B. "held the outline, emptied of the old color, while it was filled in with the new." D. "had a clear outline, and the new color came in small blotches inside, and effort spread them out to cover the whole figure." For I. the "new color came sliding in from the right side over the old, which, however, disappeared as if it were moving out of focus." With A. the new color usually came from either the lower left-hand or the upper right-hand corner. F. kept a clear outline and the new color came in from the right.
When E. found it difficult to create at the center the desired color, he thought of some object (garment, grass, sky, etc.) of that color and then transferred it to fill in the outline preserved at the center. B. moved the colored figure aside and in its place put one of the desired color, moved the new figure up to the old and there superposed it. With G. the new colors seemed of new material and there was felt to be an accumulation about the center, of old color-material. Then he located the square outside of this imaginary debris and began again. H. found that the colors of his own experiments, in which he used color squares framed in black, came to his mind at the names of the desired colors, and the association soon gave him the figure also. I. located the new colors around the presented one, first all at the right; then green at the left, red at the right, yellow above, when presented blue was at the center; then yellow and green were at the upper left-hand corner, while red came from behind. The new color 'slid in over the old.' It was found easier to secure the desired color when its position was known beforehand. J. also used a similar device. He 'turned towards the places and brought out the required color and filled the central outline with it.' He tried to break up this scheme and got red without going after it but found himself 'at a loss to find the colors.' Later he succeeded so that the required color simply appeared in the outline of the old color at the center. K. turned his eyes to corners of the central outline, then to the center, and found that this aided in developing the desired color from the corners inward. When difficulty arose, he experienced muscular tension in body and legs and jaws.
Five of the subjects considered the change from a presented color to blue the hardest and one found the change to red hardest. Green was placed second in difficulty by one, and blue second by the one who found red the hardest. Three reported the change to yellow the easiest and two the change to red.
The change from red to yellow caused 'an unpleasant sensation' in C. and the new figure 'had a maroon halo.'
A. in returning from green or blue to yellow passed through a gray; so, once, in changing from yellow to green, and once, green to red. With A. blue retinal clouds, which often came, aided changes to blue and hindered at times changes to other colors. B. had a fusion of yellow and red in changing from yellow to red. G. had a tendency to leave uncolored the lower left-hand corner and it 'was wood-colored'; G. had a gray image as the result of fusion of retinal clouds with red memory image. With H. blue always came in as robin's-egg blue, which then had to be changed to the standard blue. In one instant the green memory image seemed to shift into a purple and change to a positive retinal image which interfered with changes to other colors. J. found whistling and humming an aid in relaxing an unnatural state of tension which would hinder the best results. To increase the vividness of the image he would recall the black background on which the colored squares had hung. In one experiment K. became 'desperately tired of yellow,' which was the presented color, so that his 'mind was ready to jump to any color rather than yellow.' The returns to yellow were, in this experiment, slower than the changes from yellow.
The images sometimes changed sizes, being at times smaller, but usually larger than the object. In one experiment of C. the image was four times the size of the object, which was a green square with sides of one inch.
III. MOVEMENTS OF TWO IMAGES IN THE SAME AND IN DIFFERENT DIRECTIONS.
Table IV. gives the results of experiments in the movements of two images, the objects presented being colored squares or discs. Time of perception was five seconds. After the disappearance of after-images, if there were any, eighteen to twenty-four movements with returns to original positions were made, occupying five or six minutes. The colors were saturated blue, green, yellow and red. Four of the movements were such as separated the two images, and in four the two moved uniformly. The first four movements were right and left, left and right, up and down, down and up; the left-hand object followed the first direction indicated. The right-and-left movements involved the crossing of the images. The last four were both to right, to left, up, down. The time was taken with a stop-watch and includes the time between the director's word of command and the subject's report, 'now.' It includes, therefore, two reaction times. The subject reported the instant the colors reached, or appeared at, the suggested positions.
It is to be noticed that H. was very much slower than any of the others in making the movements, both out and back; and that K., while also slower (though much less so than H.) in making the movements outward, was no slower in making the return movements.
TABLE IV.
MOVEMENTS OF TWO IMAGES.
Twenty movements of each kind for each subject. Averages in seconds.
In Opposite Directions.
Subj. L.-R. Ret. R.-L. Ret. U.-D. Ret. D.-U. Ret.
B. 1.82 2.90 2.10 2.27 0.86 0.87 0.73 0.86
G. 3.02 2.86 2.68 2.63 1.98 2.25 1.63 2.01
H. 9.18 10.30 7.50 7.15 5.16 6.90 5.36 5.21
I. 4.17 3.52 3.40 3.37 1.26 1.47 1.23 1.31
J. 2.17 2.90 2.87 2.27 1.05 1.63 1.02 1.13
K. 5.51 6.43 5.16 4.81 1.43 1.48 1.20 1.23
Ave. 4.32 4.82 3.82 3.75 1.96 2.43 1.87 1.96
Average of all movements involving separation (480), 4.18. Returns, 2.06.
In Same Direction.
Subj. R. Ret. L. Ret. U. Ret. D. Ret.
B. 1.31 1.22 1.30 1.11 0.72 0.67 0.72 0.85
G. 2.66 2.35 3.01 2.53 2.00 1.86 2.22 1.86
H. 8.45 7.91 5.66 7.66 6.53 5.95 5.96 6.11
I. 2.57 2.27 2.13 2.05 0.97 1.26 1.00 1.13
J. 1.11 1.16 1.08 11.5 0.68 0.90 0.73 0.71
K. 3.97 3.91 3.60 4.07 1.35 1.50 1.75 1.71
Ave. 3.33 3.14 2.79 3.10 2.04 2.02 2.04 2.06
Average of all movements together (480), 3.09. Returns, 2.04.
NUMERICAL.
There were nineteen hundred and twenty movements in all, including the returns to the original positions.
In the order of difficulty as shown by the time taken, the movements stand as follows, the numbers being the averages in seconds for one hundred and twenty movements of each kind:
1. Right and left (i.e., crossing), 4.82 sec. 2. Left and right, 4.32 " 3. Up and down, 3.82 " 4. Down and up, 3.75 " 5. Both right, 3.33 " 6. Both left, 3.14 " 7. Both down, 3.10 " 8. Both up, 3.04 "
SUBJECTIVE.
In the experiments in which the time was recorded, there was no disappearance of either image except where movements were made successively. In these cases frequently the image which was awaiting its turn vanished until the first image was placed, a time varying from a quarter of a second to three or four seconds. Occasionally the image already placed would vanish, while the other was en route; the subject's attention in both these cases being centered exclusively on the image he desired to move. This was especially the case when the distances to which the images were moved were great, as to the ends of the room or to ceiling and floor. In other experiments, where, after the movements took place, the images were held for a short time, there were disappearances of one image or the other ranging from one quarter of a second to fifteen seconds, most of the absences, however, being under five seconds. The absences were more numerous in the latter half of the five minutes covered by the experiment. Occasionally a noise in the adjoining room or in the street made the images disappear.
The greater ease of vertical as compared with horizontal movements recalls an observation of Ladd,[3] in which the idioretinal light was willed into the shape of a cross. Ladd says: "The vertical bar of the cross seems much easier to produce and to hold steadily in the field." This present observation is also in accord with that described above in the case of movements of a single image.
[3] Ladd, G.T.: 'Direct Control of the Retinal Field,' PSYCH. REV., 1894, L, pp. 351-355.
On several occasions G. reported that the crossing movement was the easiest, and that the return to the original places was not easier than the other movements. In one experiment he reported the field at the center cloudy, so that it was a relief to get away from it. G.'s time records on these occasions did not support his feeling with regard to the return to the original places, but they show that the crossing movements were, in two or three instances, quicker than the 'left-and-right' movement, and the impression of promptness thus made persisted to the end of the experiment. The four movements in which both images moved uniformly were easier than the four in which movements in different directions were involved.
All the subjects were frequently conscious of eye movements, and more frequently conscious of a tendency to eye movement, which was, however, inhibited. That the strain in the eyes was practically constant during all the movements away from the original places, seems evident from the unanimous reports of a sense of relaxing and relief in the eyes, attending the movement of returning to the original places. The distance to which the images were moved was a powerful factor in producing this sense of strain. When the two images were moved and held but a few inches apart there was no sense of strain and no conscious alternation of attention. Practice increased greatly the distance at which the images could be held apart without conscious alternation of attention, but the strain of holding them apart and of inhibiting eye movement increased with the distance.
In the movements for which the time was recorded the distances varied, according to the subject, from six to eighteen inches, and varied at times with each subject. In the experiments without time record, A., B., C., E., F. and H. reported that they were able to move the images apart to ceiling and to floor, or to the opposite ends of the room, and to hold them there both in consciousness at the same time without either alternation of attention or eye movement, a tendency to which was felt but was inhibited. I. held them two feet apart without fluctuation of attention. A. reported: "I tend to turn my body to left or to right when I move the images in either of these directions." C., H. and I. said: "The eyes diverge when one image moves slowly to the right and one to the left." D. found a slight movement of the eyes which could be detected by the fingers placed lightly on the lids, when the attention was alternating between the images. K. had convergence and divergence of the eyes for crossing and separation respectively and he was accustomed to run his eye over the outline of the image. Strain in the scalp muscles was reported by A., B., E., F. and G. The up-and-down movements were universally characterized by a feeling as if one eye tended to move up and the other down. C. unconsciously inclined his head to the left in such movements as if to make the line of the two eyes parallel with the direction of the movement.
E., when holding the images two feet apart, had a strong feeling of difference of accommodation when alternating in observation and so judged the two to be in different planes.
When the movement seemed difficult the strain was greater, and when an image became dim the effort to restore its brightness or its distinctness of outline was accompanied by a feeling of bringing it nearer by accommodation and near focusing. J. found that the two images approached each other when he attempted to secure greater vividness. An analogous instance is that of A.G.C., a subject quoted in 'Mental Imagery of Students,' by French.[4] In calling up the image of a die this subject held up his hand as if it held the die. When there was no sense of strain the hand was fourteen inches from his face, but when effort was made to image all the sides of the die at once he unconsciously moved his hand to within four inches of his eyes. French says in this connection: "Situation depends on the attention involved and the inference is near that this phenomenon may be connected with feelings of convergence and accommodation which so often accompany concentrated visual attention."
[4] French, F.C.: PSYCH. REVIEW, 1902, IX., p. 40.
The movements were assisted by mentally saying, 'this image is here, that image is there,' in the case of D., G., H., I. and K.; or, at times, by articulating the names of the image, or of the color when the image was of a colored object. I. found it easy to hold outlines, but in order to retain colors in the movements of separation, he had to speak the names continually. H. also repeated the names continually, as, for example, 'violet here, orange there.'
A. represented the line of vision as going to each of the two images, which seemed connected by a line, thus making a triangle, and then pictured himself as standing off and seeing himself looking at the images. When the two objects were solid and the images were to be crossed, B. carried one image above or below the other, but when the objects were colored surfaces he conceived them as pure colors so that there was no sense of impenetrability to interfere with their crossing and they glided by each other. In the up-and-down movements he moved one at a time. C. and D. had to construct some support for the images. In most of the experiments H. first moved the images to a greater distance away, somewhat higher up and a little farther apart. In this new position the images appeared smaller and the suggested movements were made more easily. Sometimes in crossing two colored images he observed a partial mixture of the colors. J. found that a sharp movement of the head in the required direction aided materially in moving the images, and when the objects were colored surfaces fastened to the same card he found it necessary either to conceive the card as of rubber or to picture it as cut in two before he could make the movements of the images.
With A., B., C. and D. there were instances of unwilled movements of the images, in the experiments where the movements were not timed. These were much more frequent with D. than with the others, and to check them required prolonged effort. The more common movements of this sort were rotation of the image, change of its position, separation of its parts (if detachable in the object) and change of shape. E. had a return of the two images of a preceding experiment which persisted in staying a few seconds and which were as vivid as the two legitimate occupants of the mental field.
The images were duplicated five times on different days with A., and once each with C., F. and K.
A.'s cases were these. The 'wraith' of a small box whose image was out at the right, appeared above the other image off at the left and it was turned with a corner to the front. Again, at the central position each image was duplicated, the true pair being of full size, bright and distinct, the false pair small, dim and on a more distant plane, i.e., behind the others. One of the extra images persisted against all effort to banish it, for fifty-five seconds. Again, when twelve inches apart each image was similarly duplicated. In the fourth instance the images were at the center of the field. In the fifth, the right image, eight inches from the center, was duplicated, the extra image being still farther away and above. This second image was very dark, dim and vague in outline, and came and went slowly. The right image of C., when seven feet from the center, had a dim double above it. F. had moved the right-hand image (a violet disc) close to the left when a blue disc also appeared above it. Though repeating the word 'violet' he had imaged the violet disc as blue. K. was holding the two images a foot and a half apart when an extra pair appeared at the center. Both pairs persisted for sixty seconds and then the outer pair vanished, and the inner, the false pair, grew brighter.
As was said in the case of a single image, so with double images, the motion could be traced and often was traced when the movements were away from the original positions, but on the return to the original positions the images were not usually seen in transitu. For ten of the subjects, the image moved downward uniformly on an arc whose center was at the eye; and often the right and left movements were likewise on an arc. With E. the ends of the arc for motion right and left were higher also. H., I. and J. reported that all the movements were in the same plane. The upward movement was always to a less distance and the downward movement to a greater distance than the horizontal movements.
In most cases the images were the size of the percepts, in a number of cases smaller, and in a few cases larger. This was determined by comparison between the image and the percept immediately on opening the eyes and seeing the object at the end of the five minutes occupied by the experiment. A similar mode of comparison showed that, in about half of the experiments, the images were at the end of five minutes approximately equal to the percept in clearness and distinctness of outline. A comparison of these results with those obtained in a series of experiments involving passive observation of the image seems to indicate that active manipulation of the image tends to maintain the qualitative fidelity of the image when at its original position. During the progress of the experiments the reports were almost unanimous and constant that at its original position the image was vivid and distinct, but lost in both respects when away from that position, the loss being greater the greater the distance to which it was moved. Frequently there was fluctuation,—a loss of vividness and then a restoration,—which A. frequently found to be rhythmical, while in general it was evident that an increase of effort or of attention was successful in restoring lost vividness and distinctness.
D., after three minutes, read the time in the image of a watch. In superposing green on yellow, in two instances, the yellow shone through, making a mixed color, and again, in moving a green disc and a yellow disc, the green became suffused with yellow, so that the two discs were one yellow and the other greenish-yellow. For C., similarity in the two objects presented tended to make both images less vivid and distinct and to render more difficult their retention and manipulation. When one of the two objects partially overlapped the other it was difficult to separate the two images, and the area of contact was very vague in the image of the under one, and when the scrutiny reached that portion the other image returned to its original overlapping position.
IV. SUPPRESSION OF ONE OF TWO IMAGES.
The next tables (V. and VI.) give the results of experiments in suppressing one of two images, the objects presented being saturated color squares, discs, triangles, etc., placed side by side, one above the other, or a smaller one superposed on a larger. The time of perception was five seconds. After the disappearance of after-images, if there were any, the subject was directed to suppress one of the two memory images, the one to be suppressed being indicated by the director. The subject reported as soon as the indicated image disappeared, and reported any return of the suppressed image and its later disappearance in consequence of his efforts. Also he reported any disappearance and reappearance of the retained image. Five minutes was the limit of the time for the experiments with a few exceptions. The times were recorded, and those given for the first suppression include the time between the director's command and the subject's report 'now' or 'gone,' and include, therefore, two reaction times. The later suppressions include but one reaction time.
TABLE V.
SUMMARY OF ALL SUPPRESSIONS. AVERAGE TIME IN SECONDS.
[Label 1: Image Suppressed] [Label 2: No of Exper.] [Label 3: Time of First Supp.] [Label 4: Time of Ab. of Supp. Im.] [Label 5: No. of Later Supp.] [Label 6: Time of Later Supp.] [Label 7: No. of Ab. of Supp. Im.] [Label 8: Time of Ab. of Supp. Im.] [Label 9: Time of All Supp.] [Label 10: Time of All Absence of Supp. Im.]
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] Right. 46 11.59 82.39 221 8.43 216 35.74 8.94 43.93 Left. 43 11.89 79.34 175 7.79 173 44.86 8.60 51.26 Upper. 22 11.67 49.77 150 6.26 147 29.75 6.95 32.35 Lower. 17 14.23 64 71 7.88 70 46.68 9.11 50.04 Central. 42 18.24 96.93 357 3.90 352 18.13 5.41 26.54 Marginal. 20 14.25 181.57 24 8.93 24 78.08 11.35 125.12 Sundry. 7 8.71 127.21 19 13.34 19 47.27 12.09 68.78 Averages. 13.48 91.25 6.46 32.14 7.60 41.86
TABLE VI
SUPPRESSIONS GROUPED BY SUBJECTS. AVERAGE TIME IN SECONDS.
[Label 1: Subject] [Label 2: No. of Exp.] [Label 3: Time of First Supp.] [Label 4: Time of Ab. of Supp. Im.] [Label 5: No. of Later Supp.] [Label 6: Time of Later Supp.] [Label 7: No. of Ab. of Supp. Im.] [Label 8: Time of Ab. of Supp. Im.] [Label 9: Time of All Supp.] [Label 10: Time of All Ab. of Supp. Im.]
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] A. 11 28.32 11.29 117 14.90 114 10.35 16.05 10.44 B. 29 5.79 270.44 5 0.25 5 138.80 4.98 251.08 C. 18 7.88 43.08 64 3.94 63 67.49 4.81 62.07 D. 14 23.28 190.07 6 31.66 5 204.60 25.80 193.89 F. 10 12.67 86.07 230 1.95 230 67.92 2.40 10.09 G. 21 21.88 20.39 190 9.97 184 19.37 11.15 19.47 H. 21 15.27 73.27 47 10.30 47 84.48 11.84 81.02 I. 26 9.77 53.83 96 5.06 94 61.34 6.06 59.72 J. 26 3.59 32.18 209 1.40 208 31.69 1.64 31.75 K. 21 21.63 71.90 53 14.75 51 70.04 16.70 31.83 Averages. 13.48 91.25 6.46 32.14 7.60 41.86
There were ten subjects in most of the experiments, and the marked differences in the individual records which were evident in the previous experiments did not exist here except in the case of A., for whom alone the time required to obtain the suppression exceeded the time of absence of the suppressed image.
In several experiments the subjects were unable to suppress the indicated image, which in five cases was the image at the center of a disc and in two cases the outer portion of the disc. Further, five failures were by one subject, D., and one each by A. and F. The statistical report here given includes only the results of the successful experiments. Forty-four of the one hundred and ninety-seven were completely successful, as the suppressed image did not return throughout the entire period. The following table shows the grouping of the experiments according to the recurrence of the suppressed image:
Returned 0 times, 44 " 1 " 26 " 2 " 18 " 3 " 25 " 4 " 16 " 5 " 16 " 6 to 10 " 28 " more than 10 times, 24 Total, 197
Seventy-three and three fifths per cent. of all the experiments have five or fewer returns of the suppressed images.
The subjects suppressed the image as soon as possible after each return, the average time taken to accomplish these later suppressions being 6.46 sec., while the average time of absence of the suppressed image was 32.14 sec.
Including the first efforts and the first absences of the suppressed image, the average time required to suppress the image was 7.60 sec., and the average time of absence of the suppressed image was 41.86 sec.
Arranging the subjects according to the average time they required to accomplish a suppression, we have the following order. J. and F. had more recurrences of the suppressed image than any of the other subjects.
J. 1.64 sec. F. 2.40 " C. 4.80 " B. 4.98 " I. 6.06 " G. 11.15 " H. 11.84 " A. 16.05 " K. 16.70 " D. 25.80 "
Arranging them by the average absence of the suppressed image we have this order:
B. 251.08 sec D. 193.89 " H. 81.02 " C. 62.07 " I. 59.72 " K. 31.83 " J. 31.75 " G. 19.47 " A. 10.44 " F. 10.09 "
It is to be remarked, however, that the ability to keep the suppressed image out of the field increased with practice and that A. and F. had less than half the number of experiments that the rest had. D., who had but two thirds as many as most of the other subjects and therefore had less practice in suppressing the image, stands yet second in respect to this ability.
If we compare the subjects with regard to first efforts and first absences only, we obtain the following orders:
According to Ave. Time req. According to Ave. Absence for first Suppression. of Image after first Suppression. J. 3.59 sec. B. 270.44 sec. B. 5.79 " D. 190.07 " C. 7.88 " F. 86.07 " I. 9.77 " H. 73.27 " F. 12.67 " K. 71.90 " H. 15.27 " I. 53.83 " K. 21.63 " C. 43.08 " G. 21.88 " J. 32.18 " D. 23.28 " G. 20.39 " A. 28.32 " A. 11.29 "
Arranging the groups of images suppressed according to the average times of all suppressions and absences we have these orders:
Suppression. Absences. Central Images, 5.41 Marginal Images, 125.12 Upper " 6.95 Sundry " 68.78 Left " 8.60 Left " 51.26 Right " 8.94 Lower " 50.04 Lower " 9.11 Right " 43.93 Marginal " 11.35 Upper " 32.35 Sundry " 12.09 Central " 26.54
SUBJECTIVE.
Most of the subjects imaginatively placed the image to be suppressed behind the screen, in a drawer, in their closed hands, pushed it forward into the remote distance, sliced up, burned up, or pulverized and so destroyed it. B. and D. 'thought it away' directly, without mechanism or device, or got rid of it 'by a pure act of will.' Superposition was tried, frequently with success, but at times the under image shone through. When the objects were colored discs one superposed on the other, the subject spread over the whole surface the color of the image to be retained, but at times this resulted in there being two shades of the upper color, and a yellow above a red changed to an orange. When red was above yellow, the red appeared more highly illuminated. Associations with objects of the color of the retained image were found helpful but tended to modify the original color. Such associations also, at times, by secondary associations brought back the suppressed image. For example, when thinking of buttercups to enforce a yellow image, the picture of grass surrounding the flowers brought back the suppressed green image. Concentration of the attention on the image to be retained and an ignoring of the other was, on the whole, the method usually and successfully followed. This concentration was helped by imagining the image marked off into minute squares which were carefully counted. Numerous other devices of a similar character were used. Objects having many details and those lending themselves readily to suggestions of action (as a china animal) were the most helpful in enabling the subject to concentrate his attention on their image to the exclusion of another. Some subjects conceived themselves as tracing with a pencil the outline and details of the retained image. Frequently, when the two images were originally near each other and one alone was being held by close scrutiny of its parts, when this scrutiny reached the part of the image which was nearest the position of the suppressed image, the suppressed image returned. The original association between the two images was often broken up by change of the position or shape of the one to be suppressed. But devices soon became 'worn out' and new ones had to be resorted to.
Motor impulses played a large part in the process of suppression, such as head and eye movement away from the image to be suppressed, contraction of the muscles of the forehead and scalp, occasional 'setting' of the teeth, pressure together of the hands when they were supposed to be holding the image and of the knees under like circumstances. The eye traced outline and details and the more actively it could be so employed the more successful was the suppression. The sensations of accommodation and of focusing previously referred to were repeated in this series. Enunciation also was very common.
Frequent comparison of the image with the percept was made at the close of experiments and showed the utmost diversity in size, vividness and distinctness. During an experiment when the suppressed image came back, it was rarely more than a mere blur of color; in two or three instances the form came without color. Green was found to be a difficult color to hold. C. had an orange after-image from a retained yellow image, a red image having been suppressed. Between the images of a gray disc and an orange disc, three inches apart, he had a blue disc. J., while suppressing an orange disc and retaining a green disc, noticed that 'when off the fovea the whole green disc became bright orange.' There was always a sense of readiness on the part of the suppressed image to slip back. As C. expressed this, "The thing suppressed exists in the fringe of consciousness." The recurring image usually came back at its original position even when the retained image was being held in a different part of the field. In such cases the retained image at once resumed its original place.
G. and J. were successful in proportion as they freed themselves from the nervous strain of anxiety as to the result.
V. MOVEMENTS OF A SINGLE IMAGE, THE OBJECT HAVING BEEN MOVED DURING THE EXPOSURE.
In an additional series of experiments with five of the same subjects (B., G., H., I. and K.), the object was moved during the five seconds of exposure either right, left, up or down, a distance of about six to eight inches, and back again. In this way the subject was supplied with further material of a pure memory type and it was believed that some addition to our knowledge of the nature of the control of the image might thus be made by securing data contrasting the construction and the more purely reminiscent work of the imagination.
The question proposed is as follows: Does the fact that a certain movement of an object was presented to the optical perception give an advantage in time, or ease, to the mental recall of that object as so moving, over its recall as moving in other directions? The subjective experiences during such recalls may be expected to throw light upon the matter.
The subject, with closed eyes, was requested to move the mental image of the object in the four directions indicated above, returning it after each movement to its original position, and the time of each movement was recorded and, as well, the report of the subject with regard to his subjective experiences. There were sixteen hundred movements in all, eight hundred away from the original position of the image (two hundred in each of the four directions mentioned above) and eight hundred in returning to the original position.
Besides these experiments, other movements of the object during exposure were made, such as inversion, rotation, change from the vertical to the horizontal position and vice versa, rolling, oblique movements and the subjective phenomena were recorded when the subject had repeated with the image the designated movements. In all the experiments the objects were moved by the hand of the conductor of the experiment.
Table VII. gives the time record in seconds of these experiments for each subject under each of the four variations: Movement of the object to right, left, up, down.
TABLE VII.
MOVEMENTS OF A SINGLE IMAGE, THE OBJECT HAVING BEEN MOVED DURING THE TIME OF OPTICAL STIMULATION. AVERAGE TIME IN SECONDS. TEN MOVEMENTS IN EACH DIRECTION FOR EACH SUBJECT.
a. Object moved to right.
Subject R. Return L. Return Up Return Down Return Aver. B. 0.57 0.75 0.62 0.60 0.64 0.35 0.42 0.37 0.62 0.44 G. 0.55 0.60 0.55 0.57 0.57 0.27 0.25 0.27 0.25 0.26 H. 6.95 6.90 6.47 6.40 6.65 5.40 5.55 4.50 5.00 5.11 I. 2.05 2.10 2.05 2.22 2.10 1.15 1.35 1.32 1.57 1.35 K. 2.35 2.97 2.42 2.62 2.59 1.17 1.20 1.17 1.55 1.28 Ave. 2.49 2.66 2.02 2.48 2.52 1.67 1.75 1.53 1.80 1.69
Ave. to right, 2.49 Ave. of other movements, 2.52 Grand average, 2.10
b. Object moved to left. B. 0.72 0.60 0.62 0.60 0.64 0.52 0.40 0.52 0.42 0.47 G. 0.67 0.45 0.55 0.67 0.59 0.42 0.35 0.35 0.37 0.37 H. 8.22 5.95 6.52 6.42 6.78 5.82 4.10 4.37 5.55 4.96 I. 2.40 1.30 2.25 2.72 2.17 1.97 1.22 0.95 1.47 1.40 K. 2.45 2.57 2.25 2.00 2.30 1.70 1.60 1.32 1.35 1.49 Ave. 2.89 2.17 2.44 2.48 2.50 2.09 1.53 1.50 1.83 1.74
Ave. to left, 2.17 Ave. of other movements, 2.60 Grand average, 2.12
c. Object moved up. B. 0.75 0.62 0.42 0.57 0.59 0.32 0.50 0.42 0.37 0.40 G. 0.65 0.57 0.45 0.47 0.54 0.35 0.27 0.25 0.27 0.29 H. 6.77 6.25 6.85 6.15 6.57 5.27 5.55 5.30 5.30 5.35 I. 2.47 2.27 1.85 2.65 2.31 1.25 1.00 0.87 1.10 1.05 K. 3.40 2.72 1.42 2.20 2.44 1.50 1.37 1.27 1.17 1.33 Ave. 2.81 2.49 2.20 2.41 2.48 1.74 1.74 1.62 1.70 1.69
Ave. up, 2.20 Ave. of other movements, 2.57 Grand average, 2.08
d. Object moved down. B. 0.80 0.72 0.70 0.57 0.70 0.42 0.42 0.50 0.42 0.44 G. 0.60 0.60 0.55 0.47 0.55 0.25 0.25 0.27 0.27 0.26 H. 6.77 6.80 6.80 8.77 7.29 5.90 6.35 4.55 5.55 5.59 I. 2.30 2.20 2.22 1.80 2.13 1.30 1.20 1.15 1.42 1.27 K. 3.15 2.75 2.95 2.30 2.79 1.62 1.57 1.12 1.25 1.39 Ave. 2.72 2.61 2.64 2.78 2.69 1.90 1.92 1.52 1.78 1.79
Ave. down, 2.78 Ave. of other movements, 2.66 Grand average, 2.24
NUMERICAL.
As each movement may be compared with three other movements, and as there were five subjects and four variations in the conditions, there are sixty opportunities of comparing the time required to move the image in the direction in which the object was moved with the time taken to move it in the other directions. In 45 instances the time was less, in 3 the same, and in 12 greater.
These twelve instances occurred with two subjects, three (to left) occurring with K. and nine (three each right, up, down) occurring with H. The cause was the same in all twelve instances, both H. and K. reporting that (in these cases) they had great difficulty in obtaining a reasonably vivid and distinct image when directed to move the image in the direction in which the object had been moved. The attempt to move the image resulted in a vague image spread continuously over the entire area that had been covered by the moving object, and the effort to obtain the image at the desired position only was serious and took an appreciably longer time than usual. It is to be noted, also, that the time usually taken by H. is uniformly very much greater than the time taken by the other subjects. Yet, even with these instances included, the average time of all movements of the image in the direction in which the object had been moved is less than the average time of the other movements, the former being 2.41 seconds, the latter, 2.59 seconds.
TABLE VIII.
MOVEMENTS OF A SINGLE IMAGE.
I., OBJECT PREVIOUSLY MOVED; II., OBJECT NOT MOVED.
Average Time Given in Seconds.
Subjects: B. G. H. I II I II I II To right, 0.57 1.30 0.55 1.46 6.95 7.15 Return, 0.35 0.58 0.27 0.92 5.40 4.51 To left, 0.60 1.06 0.45 1.15 5.95 6.42 Return, 0.40 0.73 0.35 0.89 4.10 4.41 Up, 0.42 1.05 0.45 0.99 6.85 5.96 Return, 0.42 0.46 0.25 0.76 5.30 4.36 Down, 0.57 1.10 0.47 0.82 8.77 5.85 Return, 0.42 0.45 0.27 0.06 5.55 4.40 General 0.54 1.13 0.48 1.10 7.13 6.34 Averages, 0.40 0.55 0.28 0.66 5.09 4.42
Subjects: I. K. I II I II To right, 2.05 1.28 2.35 4.80 Return, 1.15 0.67 1.17 2.40 To left, 1.30 1.34 2.57 4.63 Retur, 1.22 0.62 1.60 2.73 Up, 1.85 1.62 1.42 3.29 Return, 0.87 0.86 1.27 1.90 Down, 1.80 1.36 2.30 3.27 Return, 1.42 0.72 1.25 1.56 General 1.75 1.40 2.16 4.00 Averages, 1.16 0.72 1.32 2.15
If the record of H. is omitted from Table VII., a, c, and d, and that of K. from VII., b (as these are the records of the twelve exceptions), the former average becomes 1.44 seconds, the latter 1.86 seconds.
The following table affords the means of comparing the time taken in moving the image in the direction in which the object had been moved with the time taken in moving the image in the same direction when there had been no movement of the object. The averages are obtained from the records of Tables VII. and I.
We have here twenty comparisons each of movements away from the original positions and movements back to the original positions:
In the first case, 15 took less time under I., 5 took more time under I.
The 5 cases of more time occurred with two subjects (H., 3 and I., 2).
In the second case, 12 took less time under I., 8 took more time under I.
The 8 cases of more time occurred with three subjects (G., 1; H., 3; I., 4).
If we omit H.'s record and take the general averages for each subject, we find the following advantages in time in form of movements where the object had been moved;
B., 0.59 seconds. G., 0.52 " K., 1.84 "
But I., 0.35 seconds in favor of movements when the object had not been moved.
Combining these results, we have 0.74 sec. as the average gain in time for these four subjects.
SUBJECTIVE.
With one exception (G.), the subjects found Movements I., movements in the direction in which the object had been moved, easier than Movements II. In Movements II. the eye seemed to construct and compel the motion, which was not the case with Movements I., in which the eye followed the motion. The distance to which the image went in Movements I. seemed predetermined, and these movements seemed exact copies of the original movement of the object, being purely reminiscent and reproducing its irregularities when there were any. Also, the image was usually seen in transitu both out and back, which was never the case with Movements II. Eye movement and enunciation were much less frequent and the image was more vivid and distinct in Movements I.
* * * * *
STUDIES IN AESTHETIC PROCESSES.
* * * * *
Transcriber's Note:
Rhythmic measures in the first 2 articles of this section are transcribed as follows:
delineates measure q quarter note q. dotted quarter note e eighth note % quarter rest
Major accent of the measure is indicated by a >, either above or in front of the beat. Minor accent of the measure is indicated by ., used in the same way.
> . q q q q or >q q .q q represent the same rhythmic pattern.
* * * * *
THE STRUCTURE OF SIMPLE RHYTHM FORMS.
BY ROBERT MACDOUGALL.
I. PROBLEMS AND METHODS OF EXPERIMENTATION.
The investigation of the problems presented by the psychological phenomena of rhythm has of late years occupied much attention and been pushed in a variety of different directions. Some researches have been concerned with an analysis of rhythm as an immediate subjective experience, involving factors of perception, reaction, memory, feeling, and the like; others have had to do with the specific objective conditions under which this experience arises, and the effect of changes in the relations of these factors; still others have sought to cooerdinate the rhythm experience with more general laws of activity in the organism, as the condition of most effective action, and to affiliate its complex phenomena upon simpler laws of physiological activity and repose; while a fourth group has undertaken a description of that historical process which has resulted in the establishment of artistic rhythm-types, and has sought to formulate the laws of their construction.[1]
[1] Description: (1) Of the psychological factors of the rhythm experience: Angell and Pierce, Ettlinger, Hauptmann, Mentz, Meumann, Stumpf, Wundt, et al. (2) Of its objective conditions and products: Binet et Courtier, Bolton, Ebhardt, Hurst and McKay, Meumann, Schumann, Sievers, et al. (3) Of its physiological accompaniments: Bolton, Bruecke, Dogiel, Hausegger, Mach, Mentz, Ribot, Sherrington, Scripture, Smith, et al. (4) Of its historical evolution: Buecher, Moritz, Scherer, et al.
This differentiation has already made such progress as to constitute the general topic a field within which specialization is called for, instead of an attempt to treat the phenomenon as a whole. It is the purpose of this paper to describe a set of experiments having to do with the second of these problems, the constitution of objective rhythm forms. In the determination of such forms it is, of course, impossible to avoid the employment of terms descriptive of the immediate experience of rhythm as a psychological process, or to overlook the constant connection which exists between the two groups of facts. The rhythm form is not objectively definable as a stable type of stimulation existing in and for itself; the discrimination of true and false relations among its elements depends on the immediate report of the consciousness in which it appears. The artistic form is such only in virtue of its arousing in the observer that peculiar quality of feeling expressed in calling the series of sensory stimuli rhythmically pleasing, or equivalent, or perfect. In no other way than as thus dependent on the appeal which their impression makes to the aesthetic consciousness can we conceive of the development and establishment of fixed forms of combination and sequence among those types of sensory stimulation which arouse in us the pleasurable experience of rhythm. The artistic rhythm form cannot be defined as constituted of periods which are 'chronometrically proportionate,' or mathematically simple. It is not such in virtue of any physical relations which may obtain among its constituents, though it may be dependent on such conditions in consequence of the subordination to physical laws of the organic activities of the human individual. The view must be subjectively objective throughout.
The need for simplicity and exactness has led to the very general employment of material as barely sensorial as could be devised for the carrying on of experiments upon rhythm. Rich tones and complex combinations of them are to be avoided, for these qualities are themselves immediate sources of pleasure, and the introduction of them into the material of experimentation inevitably confuses the analysis which the observer is called upon to make of his experience and of the sources of his pleasure in it. Still more objectionable than the presence of such complex musical tones in an investigation of rhythm is the introduction of the symbols of rational speech in concrete poetical forms. This element can be only a hindrance to the perception of pure rhythmical relations, in virtue of the immediate interest which the images called up by the verbal signs possess, and further, in view of the fact that the connections of significant thought impose upon the purely rhythmical formulation of the series of stimulations an unrelated and antagonistic principle of grouping, namely, the logical relations which the various members of the series bear to one another.
The demand for a simplification of the material which supports the rhythm experience, for the purpose of obtaining a more exact control over the conditions of experimentation, has been met by the invention of a variety of devices whereby the sequences of music, song and poetical speech have been replaced by elementary conventional symbols as the vehicle of the rhythmical impression or expression. On the one side there has commonly been substituted for musical tones and rhythmical speech the most simple, sharply limited and controllable sounds possible, namely, those due to the action of a telephone receiver, to the vibrations of a tuning-fork placed before the aperture of a resonator, or to the strokes of metallic hammers falling on their anvils. On the other side, the form of the reproduced rhythm has been clarified by the substitution of the finger for the voice in a series of simple motor reactions beaten out on a more or less resonant medium; by the use—when the voice is employed—of conventional verbal symbols instead of the elements of significant speech; and—where actual verse has been spoken—by a treatment of the words in formal staccato scansion, or by the beating of time throughout the utterance. The last of these methods is a halting between two courses which casts doubt on the results as characteristic of either type of activity. There is no question that the rhythmic forms of recitative poetry differ vastly from those of instrumental music and chanted speech. The measures of spoken verse are elastic and full of changefulness, while those of music and the chant maintain a very decided constancy of relations. The latter present determinable types of grouping and succession, while it is questionable whether the forms of relationship in spoken verse can ever be considered apart from the emotion of the moment. In so far as the rhythmic form which these differing modes of expression embody are to be made the subject of experimental investigation their characteristic structures should be kept intact as objects of analysis in independent experiments, instead of being combined (and modified) in a single process.
The apparatus employed in the course of the present investigation consisted of four different pieces of mechanism, one affording the vehicle of expression throughout the series of reproduced rhythms, the others providing the auditory material of the various rhythms apperceived but not designedly reproduced. The first of these consisted of a shallow Marey tambour, placed horizontally upon a table with its rubber film upwards, and connected by means of rubber-tubing with a pneumographic pen in contact with the revolving drum of a kymograph. A Deprez electric marker, aligned with the pneumographic stylus, afforded a time record in quarter seconds. Upon this tambour, placed within comfortable reach of the reactor's hand, the various rhythm types were beaten out. The impact of the finger-tip on the tense surface of the drum gave forth a faint and pleasing but at the same time clearly discernible and distinctly limited sound, which responded with audible variations of intensity to the differing stresses involved in the process of tapping, and which I have considered preferable to the short, sharp stroke of the Kraepelin mouth-key employed by Ebhardt. The rate of revolution in the drum was so adjusted to the normal range of excursion in the pneumographic pen as to give sharp definition to every change of direction in the curve, which hence allowed of exact measurements of temporal and intensive phases in the successive rhythm groups. These measurements were made to limits of 1.0 mm. in the latter direction and of 0.5 mm. in the former.[2]
[2] Professor Binet's doubt (L'Annee Psychologique 1895, p. 204) that the propulsion of air from the elastic chamber and the rebound of the pen might interfere with the significance of the graphic record is more serious in connection with the application of this method to piano playing than here; since its imperfection, as that writer says, was due to the force and extreme rapidity of the reactions in the former case. The present series involved only light tapping and was carried on at a much slower average rate.
The second piece of apparatus consisted of an ordinary metronome adjusted to beat at rates of 60, 90, and 120 strokes per minute. This instrument was used in a set of preliminary experiments designed to test the capacity of the various subjects for keeping time by finger reaction with a regular series of auditory stimulations.
The third piece of apparatus consisted of an arrangement for producing a series of sounds and silences, variable at will in absolute rate, in duration, and, within restricted limits, in intensity, by the interruptions of an electrical current, into the circuit of which had been introduced a telephone receiver and a rheostat. Portions of the periphery of a thin metallic disc were cut away so as to leave at accurately spaced intervals, larger or smaller extents of the original boundary. This toothed wheel was then mounted on the driving-shaft of an Elbs gravity motor and set in motion. Electrical connections and interruptions were made by contact with the edge of a platinum slip placed at an inclination to the disc's tangent, and so as to bear lightly on the passing teeth or surfaces. The changes in form of a mercury globule, consequent on the adhesion of the liquid to the passing teeth, made it impossible to use the latter medium. The absolute rate of succession in the series of sounds was controlled by varying the magnitudes of the driving weights and the resistance of the governing fans of the motor. As the relation of sounds and intervals for any disc was unalterable, a number of such wheels were prepared corresponding to the various numerical groups and temporal sequences examined one, for example, having the relations expressed in the musical symbol 3/4 >q e *; another having that represented in the symbol 4/4 >q e e ;* and so on. Variations in intensity were obtained by mounting a second series of contacts on the same shaft and in alignment with those already described. The number of these secondary contacts was less than that of the primary connections, their teeth corresponding to every second or third of those. The connections made by these contacts were with a second loop, which also contained within its circuit the telephone receiver by which the sounds were produced. The rheostatic resistances introduced into this second circuit were made to depart more or less from that of the first, according as it was desired to introduce a greater or slighter periodic accent into the series. This mechanism was designed for the purpose of determining the characteristic sequences of long and short elements in the rhythm group.
*Transcriber's Note:
The original article showed "3/4 q q q " and "4/4 q q q q ". Applying the erratum after the article (below) resulted in fewer beats per measure than indicated by the time signature. Other possibilities are "3/4 >q e q. " and "4/4 >q e e q q ".
"ERRATUM:
On page 313, line 23, the musical symbols should be a quarter note, accented, followed by an eighth note; in the following line the symbols should be a quarter note, accented, followed by two eighth notes."
The fourth piece of apparatus consisted essentially of a horizontal steel shaft having rigidly attached to it a series of metallic anvils, fifteen in number, on which, as the shaft revolved, the members of a group of steel hammers could be made to fall in succession from the same or different heights. The various parts of the mechanism and their connections may be readily understood by reference to the illustration in Plate VIII. On the right, supported upon two metal standards and resting in doubly pivoted bearings, appears the anvil-bearing shaft. On a series of shallow grooves cut into this shaft are mounted loose brass collars, two of which are visible on the hither end of the shaft. The anvils, the parts and attachments of which are shown in the smaller objects lying on the table at the base of the apparatus, consist of a cylinder of steel partly immersed in a shallow brass cup and made fast to it by means of a thumb-screw. This cup carries a threaded bolt, by which it may be attached to the main shaft at any position on its circumference by screwing through a hole drilled in the collar. The adjustment of the anvils about the shaft may be changed in a moment by the simple movement of loosening and tightening the thumb-screw constituted by the anvil and its bolt. The device by which the extent of the hammer-fall is controlled consists of cam-shaped sheets of thin wood mounted within parallel grooves on opposite sides of the loose collars and clamped to the anvils by the resistance of two wedge-shaped flanges of metal carried on the anvil bolt and acting against the sides of slots cut into the sheets of wood at opposite sides. The periphery of these sheets of wood—as exhibited by that one lying beside the loose anvils on the table—is in the form of a spiral which unfolds in every case from a point on the uniform level of the anvils, and which, by variations in the grade of ascent, rises in the course of a revolution about its center to the different altitudes required for the fall of the hammers. These heights were scaled in inches and fractions, and the series employed in these experiments was as follows: 1/8, 2/8, 3/8, 5/8, 7/8, 15/8, 24/8 inch. Upon a corresponding pair of standards, seen at the left of the illustration, is mounted a slender steel shaft bearing a series of sections of brass tubing, on which, in rigid sockets, are carried the shafts of a set of hammers corresponding in number and position to the anvils of the main axis. By means of a second shaft borne upon two connected arms and pivoted at the summit of the standards the whole group of hammers may at any moment be raised from contact with the cams of the main shaft and the series of sounds be brought to a close without interrupting the action of the motor or of the remainder of the apparatus. By this means phases of acceleration and retardation in the series, due to initial increase in velocity and its final decrease as the movement ceases, are avoided. The pairs of vertical guides which appear on this gearing-shaft and enclose the handles of the several hammers are designed to prevent injury to the insertions of the hammer shafts in their sockets in case of accidental dislocations of the heads in arranging the apparatus. This mechanism was driven by an electrical motor with an interposed reducing gear.
The intervals between the successive hammer-strokes are controlled in the following way: on the inner face of the group of pulleys mounted on the main shaft of the mechanism (this gang of pulleys appears at the extreme right in the illustration) is made fast a protractor scaled in half degrees. Upon the frame of the standard supporting these pulleys is rigidly screwed an index of metal which passes continuously over the face of the scale as the shaft revolves. The points of attachment (about the shaft) of the cams are determined by bringing the point of fall of each cam in succession into alignment with this fixed index, after the shaft has been turned through the desired arc of its revolution and made fast by means of the thumb-screw seen in the illustration at the near end of the shaft. Thus, if three strokes of uniform intensity are to be given at equal intervals apart and in continuous succession, the points of fall of the hammers will be adjusted at equal angular distances from one another, for example, at 360 deg., 240 deg., and 120 deg.; if the temporal relations desired be in the ratios 2:1:1, the arrangement will be 360 deg., 180 deg., 90 deg.; if in the ratios 5:4:3, it will be 360 deg., 210 deg., 90 deg.; and so on. If double this number of hammers be used in a continuous series the angular distances between the points of fall of the successive hammers will of course be one half of those given above, and if nine, twelve, or fifteen hammers be used they will be proportionately less.
An interruption of any desired relative length may be introduced between repetitions of the series by restricting the distribution of angular distances among the cams to the requisite fraction of the whole revolution. Thus, if an interruption equal to the duration included between the first and last hammer-falls of the series be desired, the indices of position in the three cases described above will become: 360 deg., 270 deg., 180 deg.; 360 deg., 240 deg., 180 deg., and 360 deg., 260 deg., 180 deg.. In the case of series in which the heights of fall of the various hammers are not uniform, a special adjustment must be superimposed upon the method of distribution just described. The fall of the hammer occupies an appreciable time, the duration of which varies with the distance through which the hammer passes. The result, therefore, of an adjustment of the cams on the basis adopted when the height of fall is uniform for all would appear in a reduction of the interval following the sound produced by a hammer falling from a greater height than the rest, and the amount of this shortening would increase with every addition to the distance through which the hammer must pass in its fall. In these experiments such lags were corrected by determining empirically the angular magnitude of the variation from its calculated position necessary, in the case of each higher member of the series of distances, to make the stroke of the hammer on its anvil simultaneous with that of the shortest fall. These fixed amounts were then added to the indices of position of the several cams in each arrangement of intervals employed in the experiments.
This apparatus answers a variety of needs in practical manipulation very satisfactorily. Changes in adjustment are easily and quickly made, in regard to intensity, interval and absolute rate. If desired, the gradation of intensities here employed may be refined to the threshold of perceptibility, or beyond it.
The possible variations of absolute rate and of relative intervals within the series were vastly more numerous than the practical conditions of experimentation called for. In two directions the adaptability of the mechanism was found to be restricted. The durations of the sounds could not be varied as were the intervals between them, and all questions concerning the results of such changes were therefore put aside; and, secondly, the hammers and anvils, though fashioned from the same stuff and turned to identical shapes and weights, could not be made to ring qualitatively alike; and these differences, though slight, were sufficiently great to become the basis of discrimination between successive sounds and of the recognition upon their recurrence of particular hammer-strokes, thereby constituting new points of unification for the series of sounds. When the objective differences of intensity were marked, these minor qualitative variations were unregarded; but when the stresses introduced were weak, as in a series composed of 3/8-, 2/8-, 2/8-inch hammer-falls, they became sufficiently great to confuse or transform the apparent grouping of the rhythmical series; for a qualitative difference between two sounds, though imperceptible when comparison is made after a single occurrence of each, may readily become the subconscious basis for a unification of the pair into a rhythmical group when several repetitions of them take place.
In such an investigation as this the qualification of the subject-observer should be an important consideration. The susceptibility to pleasurable and painful affection by rhythmical and arrhythmical relations among successive sensory stimuli varies within wide limits from individual to individual. It is of equal importance to know how far consonance exists between the experiences of a variety of individuals. If the objective conditions of the rhythm experience differ significantly from person to person it is useless to seek for rhythm forms, or to speak of the laws of rhythmical sequence. Consensus of opinion among a variety of participators is the only foundation upon which one can base the determination of objective forms of any practical value. It is as necessary to have many subjects as to have good ones. In the investigation here reported on, work extended over the two academic years of 1898-1900. Fourteen persons in all took part, whose ages ranged from twenty-three to thirty-nine years. Of these, five were musically trained, four of whom were also possessed of good rhythmic perception; of the remaining nine, seven were good or fair subjects, two rather poor. All of these had had previous training in experimental science and nine were experienced subjects in psychological work.
II. THE ELEMENTARY CONDITIONS OF THE APPEARANCE OF THE RHYTHM IMPRESSION.
The objective conditions necessary to the arousal of an impression of rhythm are three in number: (a) Recurrence; (b) Accentuation; (c) Rate.
(a) Recurrence.—The element of repetition is essential; the impression of rhythm never arises from the presentation of a single rhythmical unit, however proportioned or perfect. It does appear adequately and at once with the first recurrence of that unit. If the rhythm be a complex one, involving the cooerdination of primary groups in larger unities, the full apprehension of its form will, of course, arise only when the largest synthetic group which it contains has been completed; but an impression of rhythm, though not of the form finally involved, will have appeared with the first repetition of the simplest rhythmical unit which enters into the composition. It is conceivable that the presentation of a single, unrepeated rhythmical unit, especially if well-defined and familiar, should originate a rhythmical impression; but in such a case the sensory material which supports the impression of rhythm is not contained in the objective series but only suggested by it. The familiar group of sounds initiates a rhythmic process which depends for its existence on the continued repetition, in the form of some subjective accentuation, of the unit originally presented.
The rhythmical form, in all such cases, is adequately and perfectly apprehended through a single expression of the sequence.[3] It lacks nothing for its completion; repetition can add no more to it, and is, indeed, in strict terms, inconceivable; for by its very recurrence it is differentiated from the initial presentation, and combines organically with the latter to produce a more highly synthetic form. And however often this process be repeated, each repetition of the original sequence will have become an element functionally unique and locally unalterable in the last and highest synthesis which the whole series presents.
[3] When the formal key-note is distinctly given, the rhythmical movement arises at once; when it is obscure, the emergence of the movement is gradual. This is a salient difference, as Bolton, Ettlinger and others have pointed out, between subjective rhythms and those objectively supported.
Rhythmical forms are not in themselves rhythms; they must initiate the factor of movement in order that the impression of rhythm shall arise. Rhythmical forms are constantly occurring in our perceptional experience. Wherever a group of homogeneous elements, so related as to exhibit intensive subordination, is presented under certain temporal conditions, potential rhythm forms appear. It is a mere accident whether they are or are not apprehended as actual rhythm forms. If the sequence be repeated—though but once—during the continuance of a single attention attitude, its rhythmical quality will ordinarily be perceived, the rhythmic movement will be started. If the sequence be not thus repeated, the presentation is unlikely to arouse the process and initiate the experience of rhythm, but it is quite capable of so doing. The form of the rhythm is thus wholly independent of the movement, on which the actual impression of rhythm in every case depends; and it may be presented apart from any experience of rhythm.
There is properly no repetition of identical sequences in rhythm. Practically no rhythm to which the aesthetic subject gives expression, or which he apprehends in a series of stimulations, is constituted of the unvaried repetition of a single elementary form, the measures, >q. q , or >q. q q , for example. Variation, subordination, synthesis, are present in every rhythmical sequence. The regular succession is interrupted by variant groups; points of initiation in the form of redundant syllables, points of finality in the form of syncopated measures, are introduced periodically, making the rhythm form a complex one, the full set of relations involved being represented only by the complete succession of elements contained between any one such point of initiation and its return.
(b) Accentuation.—The second condition for the appearance of the rhythm impression is the periodic accentuation of certain elements in the series of sensory impressions or motor reactions of which that rhythm is composed. The mechanism of such accentuation is indifferent; any type of variation in the accented elements from the rest of the series which induces the characteristic process of rhythmic accentuation—by subjective emphasis, recurrent waves of attention, or what not—suffices to produce an impression of rhythm. It is commonly said that only intensive variations are necessary; but such types of differentiation are not invariably depended on for the production of the rhythmic impression. Indeed, though most frequently the basis of such effects, for sufficient reasons, this type of variation is neither more nor less constant and essential than other forms of departure from the line of indifference, which forms are ordinarily said to be variable and inessential. For the existence of rhythm depends, not on any particular type of periodical variation in the sensory series, but on the recurrent accentuation, under special temporal conditions, of periodic elements within such a series; and any recurrent change in quality—using this term to describe the total group of attributes which constitutes the sensorial character of the elements involved—which suffices to make the element in which it occurs the recipient of such accentuation, will serve as a basis for the production of a rhythmical impression. It is the fact of periodical differentiation, not its particular direction, which is important. Further, as we know, when such types of variation are wholly absent from the series, certain elements may receive periodical accentuation in dependence on phases of the attention process itself, and a subjective but perfectly real and adequate rhythm arise.
In this sense those who interpret rhythm as fundamentally dependent on the maintenance of certain temporal relations are correct. The accentuation must be rhythmically renewed, but the sensory incentives to such renewals are absolutely indifferent, and any given one of the several varieties of change ordinarily incorporated into rhythm may be absent from the series without affecting its perfection as a rhythmical sequence. In piano playing the accentual points of a passage may be given by notes struck in the bass register while unaccented elements are supplied from the upper octaves; in orchestral compositions a like opposition of heavy to light brasses, of cello to violin, of cymbals to triangle, is employed to produce rhythmical effects, the change being one in timbre, combined or uncombined with pitch variations; and in all percussive instruments, such as the drum and cymbals, the rhythmic impression depends solely on intensive variations. The peculiar rhythmic function does not lie in these elements, but in a process to which any one of them indifferently may give rise. When that process is aroused, or that effect produced, the rhythmic impression has been made, no matter what the mechanism may have been.
The single objective condition, then, which is necessary to the appearance of an impression of rhythm is the maintenance of specific temporal relations among the elements of the series of sensations which supports it. It is true that the subjective experience of rhythm involves always two factors, periodicity and accentuation; the latter, however, is very readily, and under certain conditions inevitably, supplied by the apperceptive subject if the former be given, while if the temporal conditions be not fulfilled (and the subject cannot create them) no impression of rhythm is possible. The contributed accent is always a temporally rhythmical one, and if the recurrence of the elements of the objective series opposes the phases of subjective accentuation the rhythm absolutely falls to the ground. Of the two points of view, then, that is the more faithful to the facts which asserts that rhythm is dependent upon the maintenance of fixed temporal intervals. These two elements cannot be discriminated as forming the objective and subjective conditions of rhythm respectively. Both are involved in the subjective experience and both find their realization in objective expressions, definable and measurable.
(c) Rate.—The appearance of the impression of rhythm is intimately dependent on special conditions of duration in the intervals separating the successive elements of the series. There appears in this connection a definite superior limit to the absolute rate at which the elements may succeed one another, beyond which the rapidity cannot be increased without either (a) destroying altogether the perception of rhythm in the series or (b) transforming the structure of the rhythmical sequence by the substitution of composite groups for the single elements of the original series as units of rhythmic construction; and a less clearly marked inferior limit, below which the series of stimulations fails wholly to arouse the impression of rhythm. But the limits imposed by these conditions, again, are cooerdinated with certain other variables. The values of the thresholds are dependent, in the first place, on the presence or absence of objective accentuation. If such accents be present in the series, the position of the limits is still a function of the intensive preponderance of the accented over the unaccented elements of the group. Further, it is related to the active or passive attitude of the aesthetic subject on whom the rhythmical impression is made, and there appear also important individual variations in the values of the limits.
When the succession falls below a certain rate no impression of rhythm arises. The successive elements appear isolated; each is apprehended as a single impression, and the perception of intensive and temporal relations is gotten by the ordinary process of discrimination involved when any past experience is compared with a present one. In the apprehension of rhythm the case is altogether different. There is no such comparison of a present with a past experience; the whole group of elements constituting the rhythmic unit is present to consciousness as a single experience; the first of its elements has never fallen out of consciousness before the final member appears, and the awareness of intensive differences and temporal segregation is as immediate a fact of sensory apprehension as is the perception of the musical qualities of the sounds themselves. |
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