Harvard Psychological Studies Part 26

In short, it appears that though much has been said and done upon the general subject of psychical inhibition, experimental inquiry into the inhibitory effect of one idea upon another--abstraction made, as far as possible, of all volitional influence--virtually introduces us to a new phase of the subject.

The term 'idea,' it should be noted, is here used in its broadest sense, and includes the memory image. In fact, the memory image and its behavior in relation to another memory image formed the material of the first part of the research, which alone is reported here.

Apparatus and method were both very simple.

The ideas to be compared were suggested by geometrical figures cut out of pasteboard and hung, 25 cm. apart, upon a small black stand placed on a table in front of the observer, who sat at a distance of four feet from the stand. The diagrams and descriptions which follow will show the character of these figures.

Before the figures were placed in position, the subject was asked to close his eyes. The figures being placed, a few seconds' warning was given, and at the word 'look' the subject opened his eyes and looked at the objects, closing his eyes again at the word 'close.' The time of exposure was five seconds. This time was divided as equally as possible between the two figures, which were simultaneously exposed, the observer glancing freely from one to the other as in the common observation on which our ideas of objects are founded. At the end of the exposure the subject sat with closed eyes and reported the several appearances and disappearances of the ideas or mental images of the objects just presented. The conditions required of him were that he should await pa.s.sively the entry of the rival claimants on his attention, favoring neither and inhibiting neither; that is to say, he was to remit all volitional activity, save so far as was necessary to restrict his attention to the general field upon which the ideated objects might appear, and to note what occurred on the field. The period of introspection, which followed immediately the disappearance of such retinal images as remained, after the closing of the eyes to the external objects, lasted sixty seconds. The reports, like the signals, were given in a just audible tone. They were in such terms as 'right--left,' 'small--large,' 'circle--star,' terms the simplest that could be found, or such as seemed, in any given case, most naturally or automatically a.s.sociated with the object, and therefore least likely to disturb the course of the observation. And each report was noted down by the experimenter at the instant it was given, with the time of each phase, in seconds, as indicated by a stop-watch under the experimenter's eye.

It will be remarked that the att.i.tude required of the observer was one which is not commonly taken. And it may be objected that the results of an att.i.tude so unusual towards objects so ghostly and attenuated must be too delicate, or too complex, or influenced by too many alien suggestions, to be plumply set down in arabic numerals. The subjects, in fact, did at first find the att.i.tude not easy to a.s.sume. A visual object may hold the attention by controlling the reflexes of the eye.

But an ideational object has ordinarily no sure command of the conscious field save under the influence of a volitional idea or some strongly toned affectional state. But with a little practice the difficulty seemed to disappear. The subject became surer of his material, and the mental object gradually acquired the same sort of individuality as the visual object, though the impression it made might be less intense.

After a few preliminary experiments, figures were devised for the purpose of testing the effect of mere difference in the complexity of outline. That is to say, the members of every pair of objects were of the same uniform color-tone (Bradley's neutral gray No. 2), presented the same extent of surface (approximately 42 sq. cm.), were exposed simultaneously for the same length of time (5 seconds), and were in contour usually of like general character save that the bounding line in the one was more interrupted and complex than in the other.

In another series the variant was the extent of surface exposed, the color-tone (neutral gray), outline, and other conditions being the same for both members of each pair. The smaller figures were of the same area as those of the preceding series; in the larger figures this area was doubled. Only one member of each pair is represented in the diagrams of this and the next series.

In a third series brightness was the variant, one member of each pair being white and the other gray (Bradley's cool gray No. 2). All other conditions were for both figures the same.

In still another series strips of granite-gray cardboard half a centimeter wide were cut out and pasted on black cards, some in straight and some in broken lines, but all of the same total length (10 cm.). These were exposed under the same general conditions as those which have already been described, and were intended to show the relative effects of the two sorts of lines.

TABLE I.

1 2 3 4 5 Totals. Averages.

L R L R L R L R L R L R L R I. 45 45 25 29 27 27 31 24 36 20 164 145 32.8 29 II. 20 25 28 28 28 19 31 31 28 14 135 117 27 23.5 III. 11 12 17 28 0 7 0 15 27 23 55 85 11 17 IV. 7 6 47 22 17 21 17 45 31 30 119 124 23.8 24.8 V. 27 33 46 36 40 31 44 31 26 35 183 165 36.6 33.2 VI. 11 14 32 29 34 21 14 35 0 46 91 145 18.2 29 VII. 36 33 30 30 50 50 22 22 52 52 190 187 38 37.4 VIII. 41 44 33 33 45 45 34 44 37 28 190 194 38 38.8 IX. 45 45 39 46 42 47 47 47 44 44 217 229 43.4 45.8 X. 40 39 24 25 19 21 21 23 18 25 122 133 24.4 26.6 XI. 51 53 52 50 42 42 42 42 42 42 229 229 45.8 45.8

334 349 373 356 344 331 303 359 341 359 1695 1754 30.8 31.9

The Arabic numerals at the head of the columns refer, in every table, to the corresponding numerals designating the objects in the diagram accompanying the table.

_L_: left-hand object.

_R_: right-hand object.

The Roman numerals (_I_ to _XI_) indicate the different subjects. The same subjects appear in all the experiments, and under the same designation. Two of the subjects, _IV_ and _VIII_, are women.

The numbers under _L_ and _R_ denote the number of seconds during which the left-hand image and the right-hand image, respectively, were present in the period of introspection (60 seconds).

General average: _L_, 30.8 sec.; _R_, 31.9 sec.

[Ill.u.s.tration: FIG. 1.]

_Series No. 1._--For the purpose of obtaining something that might serve as a standard of comparison, a series of observations was made in which the members of every pair were exact duplicates of each other, and were presented under exactly the same conditions, spatial position of course excepted. The records of these observations are for convenience placed first as Table I.

In treating the facts recorded in the accompanying tables as phenomena of inhibition no a.s.sumption is implied, it may be well to repeat, that the ideational images are forces struggling with each other for mastery. Nor is it implied, on the other hand, that they are wholly unconditioned facts, unrelated to any phenomena in which we are accustomed to see the expression of energy. Inhibition is meaningless save as an implication of power lodged somewhere. The implication is that these changes are conditioned and systematic, and that among the conditions of our ideas, if not among the ideas themselves, power is exerted and an inferior yields to a superior force. Such force, in accordance with our general presupposition, must be neural or cerebral. Even mental inhibition, therefore, must ultimately refer to the physical conditions of the psychical fact. But the reference, to have any scientific value, must be made as definite as the case will allow. We must at least show what are the conditions under which a state of consciousness which might otherwise occur does not occur.

When such conditions are pointed out, and then only, we have a case of what has been called psychical inhibition; and we are justified in calling it inhibition because these are precisely the conditions under which physiological inhibition may properly be inferred. And, we may add, in order that the conditions may be intelligibly stated and compared they must be referable to some objective, cognizable fact.

Here the accessible facts, the experiential data, to which the psychical changes observed and the cerebral changes a.s.sumed may both be referred, are visual objects, namely, the figures already described.

What may occur when these objects are precisely alike, and are seen under conditions in all respects alike except as to spatial position, is indicated in Table I. The general average shows that the image referred to the left-hand object was seen some 30 seconds per minute; that referred to the right-hand image, some 31 seconds. Sometimes neither image was present, sometimes both were reported present together, and the time when both were reported present is included in the account. In this series it appears, on the whole, that each image has about the same chance in the ideational rivalry, with a slight preponderance in favor of the right. Individual variations, which may be seen at a glance by inspection of the averages, show an occasional preponderance in favor of the left. But the tendency is, in most cases, towards what we may call right-handed ideation.

_Series No. II._--In the second series (Table II.) we find that, other things being equal, _an increase in the relative complexity of the outline favors the return of the image to consciousness_. Including the time when both images were reported present at once, the simpler appears but 27 seconds per minute as against 34 seconds for the more complex. No attempt was made to arrange the figures on any regularly increasing scale of complexity so as to reach quant.i.tative results.

The experiment was tentative merely.

TABLE II.

1 2 3 4 S C S C S C S C I. 21.5 23.5 14.5 35 22.5 21.5 15 27 II. 35.5 21.5 32.5 48 32 33.5 32.5 21.5 III. 27.5 39 20.5 47.5 24.5 46.5 8 22.5 IV. 31.5 26.5 38 23.5 34.5 22 24 29.5 V. 48 50 48 39.5 41.5 51.5 51 47.5 VI. 11.5 35 26.5 28.5 21 33 29 17 VII. 29.5 35 47 47 10.5 52 29.5 33.5 VIII. 12.5 41 32 28.5 13 26.5 17 41.5 IX. 10.5 25.5 27.5 34.5 14.5 44 33 44.5 X. 24 25.5 20 23 16.5 28 23 21 XI. 46 46.5 31.5 53.5 18 53.5 27 50.5

298 369 338 408.5 248.5 412 289 356

5 6 7 Averages.

S C S C S C S C I. 20.5 21 14.5 27 7.5 37.5 16.57 27.50 II. 31.5 32 50 45.5 49.5 39.5 37.64 34.50 III. 19.5 32.5 13 31 29 18 20.28 33.85 IV. 40.5 46.5 27 30.5 26 32 31.64 30.07 V. 47.5 47.5 50.5 48.5 38 38 46.35 46.07 VI. 14.5 29 14 33 21 28.5 19.64 29.14 VII. 25.5 43 42.5 30 28 41.5 30.35 40.28 VIII. 8 34 24 27 33 14.5 19.92 30.42 IX. 41.5 27 29.5 27.5 29.5 28 26.57 33.00 X. 10.5 36.5 17 27 18 25 18.42 26.57 XI. 21.5 53.5 40.5 43.5 30 45 30.64 49.42

281 402.5 322.5 370.5 309.5 347.5 27.10 34.62

_S:_ Outline simple.

_C:_ Outline complex.

In this and the following tables the numbers in the body of the columns represent, in each case, the combined result of two observations, in one of which the simpler figure was to the left, in the other the more complex. The figures were transposed in order to eliminate any possible s.p.a.ce error.

General average: _S_, 27.10 sec.; _C_, 34.62 sec.

Can anything be said, based on the reports, by way of explanation of the advantage which complexity gives? In the first place, the att.i.tude of the subject towards his image seems to have been much the same as his att.i.tude towards an external object: to his observation the image became, in fact, an object. "When the image was gone," says one, "my eyes seemed to be in search of something." And occasionally the one ideated object was felt to exert an influence over the other. "The complex seemed to affect the form of the simpler figure." "It seemed that the complex actually had the effect of diminishing the size of the simpler figure." From time to time the images varied, too, in distinctness, just as the objects of perception vary, and the superior distinctness of the more complex was frequently noted by the subjects.

Now the importance of the boundary line in perception is well understood. It seems to have a corresponding importance here. "What I notice more in the simple figure," says one observer, "is the ma.s.s; in the complex, the outline." "The simple seemed to lose its form," says another, "the complex did not; the jagged edge was very distinct." And it is not improbable, in view of the reports, that irregularities involving change of direction and increase in extent of outline contributed mainly to the greater persistence of the more complicated image, the 'ma.s.s' being in both figures approximately the same. Nor did the advantage of the broken line escape the notice of the subject.

"I found myself," is the comment of one, "following the contour of the star--exploring. The circle I could go around in a twinkle." Again, "the points entered the field before the rest of the figure." And again, "the angle is the last to fade away."

[Ill.u.s.tration: FIG. 2.]

Now this mental exploration involves, of course, changes in the direction of the attention corresponding in some way to changes in the direction of the lines. Does this shifting of the attention involve ideated movements? There can be little doubt that it does. "I felt an impulse," says one, "to turn in the direction of the image seen." And the unconscious actual movements, particularly those of the eyes, which are a.s.sociated with ideated movements, took place so often that it is hard to believe they were ever wholly excluded. Such movements, being slight and automatically executed, were not at first noticed.

The subjects were directed, in fact, to attend in all cases primarily to the appearance and disappearance of the images, and it was only after repeated observations and questions were put, that they became aware of a.s.sociated movements, and were able, at the close of an observation, to describe them. After that, it became a common report that the eyes followed the attention. And as we must a.s.sume some central influence as the cause of this movement, which while the eyes were closed could have no reflex relation to the stimulus of light, we must impute it to the character of the ideas, or to their physical substrates.

The idea, or, as we may call it, in view of the att.i.tude of the subject, the internal sensory impression, thus seems to bear a double aspect. It is, in the cases noted, at once sensory and motor, or at any rate involves motor elements. And the effect of the activity of such motor elements is both to increase the distinctness of the image and to prolong the duration of the process by which it is apprehended.

The sensory process thus stands in intimate dependence on the motor.

Nor would failure to move the eyes or any other organ with the movement of attention, if established, be conclusive as against the presence of motor elements. A motor impulse or idea does not always result in apparent peripheral movement. In the suppressed speech, which is the common language of thought, the possibility of incipient or incomplete motor innervations is well recognized. But where the peripheral movement actually occurs it must be accounted for. And as the cause here must be central, it seems reasonable to impute it to certain motor innervations which condition the shifting of the mental att.i.tude and may be incipient merely, but which, if completed, result in the shifting of the eyes and the changes of bodily att.i.tude which accompany the scrutiny of an external object. And the sensory process is, to some extent at least, conditioned by the motor, if, indeed, the two are anything more than different aspects of one and the same process.[7]

[7] Cf. Munsterberg, H.: 'Grundzuge d. Psychologie,' Bd. I., Leipzig, 1900, S. 532.

But where, now, the subject is occupied in mentally tracing the boundaries of one of his two images he must inhibit all motor innervations incompatible with the innervations which condition such tracing: the rival process must cease, and the rival image will fade.

He may, it is true, include both images in the same mental sweep. The boundary line is not the only possible line of movement. In fact, we may regard this more comprehensive glance as equivalent to an enlargement of the boundaries so as to include different mental objects, instead of different parts of but one. Or, since the delimitation of our 'objects' varies with our att.i.tude or aim, we may call it an enlargement of the object. But in any case the mental tracing of a particular boundary or particular spatial dimensions seems to condition the sense of the corresponding content, and through inhibition of inconsistent movements to inhibit the sense of a different content. No measure of the span of consciousness can, of course, be found in these reports. The movements of the attention are subtle and swift, and there was nothing in the form of the experiments to determine at any precise instant its actual scope. All we need a.s.sume, therefore, when the images are said to be seen together, is that neither has, for the time being, any advantage over the other in drawing attention to itself. If in the complete observation, however, any such advantage appears, we may treat it as a case of inhibition.

By definition, an idea which a.s.sumes a place in consciousness which but for itself, as experiment indicates, another might occupy, inhibits the other.

[Ill.u.s.tration: FIG. 3.]

TABLE III.

1 2 3 4 5 6 S L S L S L S L S L S L I. 22 24 19.5 23 20 26 21.5 21 21 26 18 31 II. 31 39 31.5 36 15 32.5 11 22.5 13.5 24.5 7.5 23 III. 10.5 43.5 12 21.5 13 14.5 19 10.5 18.5 30.5 7 18.5 IV. 34.5 29.5 29.5 24 40.5 33 30.5 32.5 15 30 26 30 V. 31.5 30 42 45 39 51 47 49.5 41 37 46 45 VI. 22 20 20.5 22 23.5 22 25 16 24 20 22 25.5 VII. 53.5 53.5 23.5 23.5 47.5 47.5 51 52 52.5 53 51 52 VIII. 34 40.5 23 29 21 22 22 37.5 34.5 35 27.5 28 IX. 19.5 45 19.5 46 22 23.5 23.5 48 26 45.5 19 44.5 X. 16 30.5 12 35 21 24.5 8.5 41 15.5 33 19 28 XI. 38.5 36.5 21 48.5 30 54.5 31 55.5 32 54 12 50