Harvard Psychological Studies Part 30

RECAPITULATION.

Seconds Seconds.

1 Figures alike: Left 30.8 Right 31.9 2 " unlike: Simple 27.10 Complex 34.62 3 " " Small 24.54 Large 33.30 4 " " Gray 25.61 White 29.53 5 " " Line 31.91 Angle 38.54 6 " " Plain 23.92 Marked 37.48 7 " " (colored) 5 seconds 27.75 10 seconds 29.15 8 " " (gray) 5 seconds 25.42 10 " 32.12 9 " " 1st exposure 12.64 2d exposure 36.45 10 " " Vertical line 34.94 Hor. line 34.49 11 " " Full-faced 28.10 Outline 41.08 12 " " Figure 29.26 Int. lines 39.32 13 " " Figure 34.03 Vert. lines 36.40 14 " " Stationary 28.88 Moved 37.39 15 " " Gray 30.90 Colored 37.81 16 (See Table XVI.)

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 h.o.m.ogeneous 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 h.o.m.ogeneous 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 cla.s.sic 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 cla.s.sifying 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 att.i.tudinize 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 cla.s.sify 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 gla.s.s ball, a book, a silk purse, an eye-gla.s.s 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.