Chapter XI: Section II: showed that the shorter filled distances are (7)

For two of the subjects, _M_ and _Mo_, the time intervals between the tests remained as in the _A_ and the _B_ sets, namely, two days, nine days, and sixteen days. With the four other subjects, _S, Hu, B,_ and _Ho_, the number of tests was reduced to three and the intervals were as follows:

The I. test, which as before was a part of the learning process, was not counted. The II. test followed from 4½ to 6½ hours, or an average of 5-3/8 hours, after the I. test. The III. test was approximately 16 hours after the II. test for all four subjects.

The series were learned between 10 a.m. and 1:30 p.m., the II. test was the same day between 4:30 and 5:10 p.m., and the III. test was the following morning between 8:30 and 9:10 a.m. Each subject of course came at the same hour each week.

Each series was shown three times, as in the _B_ set.

A change had to be made in the length of exposure of each couplet in the movement series. For, as a rule, movements employing objects required a longer time to execute than mere movements of the body. Five seconds was found to be a suitable length of exposure. To keep the three other types of series comparable with the movement series, if possible, their exposure was also increased from 3 to 5 secs. The interval of 2 secs, at the end of a presentation was omitted, and the interval between learning and testing reduced from 4 secs, in the _B_ set to 2 secs.

In the movement series of the _A_ and _B_ sets, movements of parts of the body were chosen. But the number of such movements which a person can conveniently make while reading words shown through an aperture is limited, and as stated above no single word was ever used in two couplets. These were now exhausted. In the _C_ set, therefore, movements employing objects were substituted. The objects lay on the table in a row in front of the subject, occupying a space about 50 cm. from left to right, and were covered by a black cambric cloth. They were thus all exposed at the same moment by the subject who, at a signal, laid back the cloth immediately before the series began, and in the same manner covered them at the end of the third presentation. Thus the objects were or might be all in view at once, and as a result the subject usually formed a single mental image of the four objects.

With this kind of material it was no longer necessary for the operator to show the subject in advance of the series what the movements were in order to avoid hesitation and confusion, for the objects were of such a nature as obviously to suggest in connection with the words the proper movements.

TABLE IV.

SHOWING RECALL AFTER TWO, NINE AND SIXTEEN DAYS FOR TWO SUBJECTS, AND
AFTER FIVE HOURS AND TWENTY-ONE HOURS FOR FOUR OTHER SUBJECTS.

Days. Two. Nine. Sixteen Two. Nine. Sixteen
N. O. N. O. N. O. V. M. V. M. V. M.
Series _M._
C^{1-4} 4 4 4 4 3 2 3 2 2 2 1 1
C^{5-8} 2 2 2 2 2 1 1 1 1 2 1 0
C^{9-12} 3 2 3 1 3 0 2 4 3 2 2 1
C^{13-16} 4 3(1) 4 2(1) 4 2(1) 3 4 2 3 2 3
Total 13 1(1) 13 9(1) 12 5(1) 9 11 8 9 6 5
Per cent. 81 73 81 60 75 33 56 69 50 56 38 31

_Mo_
C^{1-4} 2 4 1 1 1 1 1 4 1 2 1 2
C^{5-8} 3 2 4 1 3 1 4 3(1) 4 3(1) 2 2(1)
C^{9-12} 0 1 0 1 0 1 0 3 0 1 0 2
C^{13-16} 0 0(1) 0 0(1) 0 0(1) 1(1) 4 1(1) 2 0(1) 0
Total 5 7(1) 5 3(1) 4 3(1) 6(1) 14(1) 6(1) 8(1) 3(1) 6(1)
Per cent. 31 46 31 20 25 20 40 93 40 53 20 40

Hours. Five. Twenty-one. Five. Twenty-one
N. O. N. O. V. M. V. M.
Series _S._
C^{1-4} 1 3 1 1 0 1 0 1
C^{5-8} 0(1) 3 0 2 0 1 0 1
C^{9-12} 0(1) 3 0(1) 4 3 4 3 4
C^{13-16} 1 3 1 3 2 3(1) 3 3(1)
Total 2(2) 12 2(1) 10 5 9(1) 6 9(1)
Per cent. 14 75 14 63 33 60 40 60

_Hn._
C^{1-4} 1 4 1 4 0 4 1 4
C^{5-8} 0(2) 1 0(2) 1 0(1) 2 1(1) 2(2)
C^{9-12} 3 4 3 4 2 4 2 4
C^{13-16} 1 3 3 3 0 3(1) 0 2(1)
Total 5(2) 12 7(2) 12 2(1) 13(3) 4(1) 12(3)
Per cent. 36 75 50 75 14 100 29 92

_B._
C^{1-4} 3 4 3 4 3 4 3 4
C^{5-8} 3 2 3 3 2 2 2 4
C^{9-12} 2 4 2 3 2 1 2 2
C^{13-16} 3 4 3 4 2 4 2 4
Total 11 14 11 14 9 11 9 14
Per cent. 69 88 69 88 56 69 56 88

_Ho._
C^{1-4} 3(1) 2(2) 3(1) 2(2) 0 3(1) 0 1(1)
C^{5-8} 3(1) 4 3(1) 4 3 3(1) 3 3(1)
C^{9-12} 1(2) 4 1(2) 4 2(1) 3(1) 2(1) 3(1)
C^{13-16} 0 2 0 2 2 4 2 4
Total 7(4) 12(2) 7(4) 12(2) 7(1) 13(3) 7(1) 11(3)
Per cent. 58 92 58 92 50 100 50 85

The object series were also changed to conform to the movement series. Formerly the objects had been shown successively through the aperture and synchronously with their corresponding words; now they were on the table in front of the subject and all uncovered and covered at once as in the movement series. The subjects therefore had a single mental image of these four objects also.

In both the object and the movement series the objects as before were small and fairly uniform in size and so selected as not to betray to the subject their presence beneath the cloth in the I. test. In the II., III. and IV. tests there were no objects on the table.

The previous table shows the results of the _C_ set. The figures give the number of couplets correct out of four; the figures in brackets give the number of indirect associations; the total number recalled in any series is their sum.

In the following summary the recall of _M_ and _Mo_ after two days and of _S, Hu, B_ and _Ho_ after twenty-one hours are combined.

SUMMARY FROM TABLE IV.

N. O. V. M.
_M._ 81 per cent. 73 per cent. 56 per cent. 69 per cent.
_Mo._ 31 " 46 " 40 " 93 "
_S._ 14 " 63 " 40 " 60 "
_Hu._ 50 " 75 " 29 " 92 "
_B._ 69 " 88 " 56 " 88 "
_Ho._ 58 " 92 " 50 " 85 "
----------- ----------- ----------- -----------
Av. 51 per cent. 73 per cent. 45 per cent. 81 per cent.

Av. gain in object couplets, 22 per cent.
" " " movement couplets, 36 per cent.

Before asking whether the results of the _C_ set confirm the conclusions already reached, we must compare the conditions of the three sets to see whether the changes in the conditions in the _C_ set have rendered it incomparable with the other two. The first change was the substitution of dissyllabic words in the verb and the movement series in the place of monosyllabic words. Since the change was made in both the verb and the movement series their comparability with each other is not interfered with, and this is the point at issue. Preliminary tests, however, made it highly probable that simple concrete dissyllabic words are not more difficult than monosyllabic in 5 secs. exposure. This change is therefore disregarded.

The first important change introduced in the _C_ set was the reduction of the intervals between the tests for four subjects. The second was the lengthening of the exposure from 3 to 5 secs. These changes also do not lessen the comparability of the noun, object, verb and movement series with one another, since they affected all series of the _C_ set.

The third change in the conditions was the substitution in the movement series of movements employing objects for movements of the body alone, and the consequent placing of objects on the table in the movement and in the object series of which the subject obtained a single mental image. All of the subjects were of the opinion that this single mental image was an aid in recall. Each of the objects contributing to form it was individualized by its spatial order among the objects on the table. The objects shown through the aperture were connected merely by temporal contiguity. On this account the object and the movement series of the _C_ set are not altogether comparable with those of the _A_ and the _B_ sets. We should expect _a priori_ that the object and the movement series in the _C_ set would be much better recalled than those of the _A_ and the _B_ sets.

The fourth change was from imaged or made movements of the body alone to imaged or made movements employing objects. If, as the _A_ and the _B_ sets have already demonstrated, the presence of objects at all is an aid to recall, the movement series of the _C_ set should show a greater gain over their corresponding verb series than the simple movements of the body in the _A_ and the _B_ sets showed over their corresponding verb series. For, employing objects in movements is adding the aid of objects to whatever aid there is in making the movements.

Turning to the results, we consider the _C_ set by itself with reference to the effect of the use of objects vs. images in general. The summary from Table IV. shows that under the conditions given, after intervals of from slightly less than one day to two days, five of the six subjects recall object couplets better than noun couplets. One subject, _M_ recalls noun couplets better. It also shows that under the conditions and after the intervals mentioned all six subjects recall movement couplets better than verb couplets. In view of the small difference here and of his whole record, however, _M_ is probably to be classed as indifferent in both substantive and action series.

RECALL AFTER NINE AND SIXTEEN DAYS.

Thus far recall after these longer intervals has not been discussed. The experiment was originally devised to test recall after two days only, but it was found that with two of the subjects, _M_ and _Mo_, recall for greater intervals could be obtained with slight additional trouble. This was accordingly done in the _B_ and _C_ sets. The results of the four other subjects in the _B_ set are not so satisfactory on this point, because not enough was recalled.

The most interesting fact which developed was an apparently slower rate of forgetting, in many cases, of the nouns and verbs than of the objects and movements. In the noun-object group of the _B_ set it is noticeable in three out of the four possible subjects, viz., _B, Ho_, and _Mo_. _M_ alone does not show it. The two other subjects, _S_ and _B_, did not recall enough for a comparison. In the verb-movement group of the _B_ set it is also marked in three out of the four possible subjects, viz., _M_, _Ho_, and _Mo. B_ alone does not show it. It is also seen in the _C_ set in the results of _M_ and _Mo_, in both the noun-object and the verb-movement groups. With the four other subjects in the _C_ set it could not be noticed, since the series ran their course in a day. In _M_ (verb-movement group, _C_ set) and _Mo_ (noun-object group, _C_ set) the originally higher object or movement curves actually fall below their corresponding noun or verb curves.

The results of the tests for recall after nine and sixteen days are summarized in the following tables. They should be compared with the recall of these same series after two days given in Tables II. and IV., nor should it be forgotten that all four types started with perfect immediate recall. The figures give per cents, correct after eliminating indirect-association couplets.

TABLE V.

SHOWING RECALL AFTER NINE AND SIXTEEN DAYS.--SUMMARY FROM _B_ SET.

Days. Nine. Sixteen Nine. Sixteen.
N. O. N. O. V. M. V. M.
_M._ 36 38 29 31 56 19 50 31
_S._ 0 6 0 6 0 7 0 0
_Hu._ 0 7 0 20 0 25 0 6
_B._ 13 21 13 13 7 20 7 13
_Ho._ 25 23 17 0 25 33 0 8
_Mo._ 57 63 57 56 20 79 20 69
Av. 22 26 19 21 18 31 13 21

TABLE VI.

SAME FOR _M_ AND _Mo_.--SUMMARY FROM _C_ SET.

Days. Nine. Sixteen. Nine. Sixteen.
N. O. N. O. V. M. V. M.
_M_. 81 60 75 33 50 56 38 31
_Mo_. 31 20 25 20 40 53 20 40

THE _D_ SET.

A few series of nouns, objects, verbs, and movements dissociated from foreign symbols were obtained. The material was of the same kind as the words used in the couplet series, being mostly monosyllabic and seldom dissyllabic words. They had not been previously used with these subjects. Each series contained ten words or ten objects. The same kind of precautions were taken as in the couplet sets to avoid phonetic aids and the juxtaposition of words which suggest each other. The apparatus employed in the couplet sets was used. The objects in the object series were shown through the aperture. Visual images were required in the noun and in the verb series. The noun and the object series were exposed at the rate of one word every 2 secs. (or 20 secs. for the series) for _M_, _S_, and _Hu_, and one every 3 secs. (or 30 secs. for the series) for _B_, _Ho_, and _Mo_. Only one exposure of the series was given. At its completion the subject at once wrote as many of the words or objects as he could recall. Two days later at the same hour he was asked to write without further stimulus as many words of each series as he could recall, classifying them according to their type of series.

The verbs were similar to the verbs of the couplet series. There was a tendency in the verb series among most of the subjects to make a more or less connected story of the verbs and thus some subjects could retain all ten words for two days. This was an element not present in the couplet verb series, according to the subjects, nor in any other series, and the subjects were, therefore, directed to eliminate it by imaging each action in a different place and connected with different persons. The effort was nearly successful, some of the subjects connecting two or three verbs, and others none. The movements employed ten objects which were uncovered and covered by the subject as in the _C_ set. The exposure for the verbs and movements was 5 secs. for each word, or 50 secs. for the series. The tests were the same as in the series of ten nouns and ten objects, but in a number of cases (to be specified in the table) it seemed best to shorten the interval for deferred recall to one day.

The series were always given in pairs--a noun and an object series, or a verb and a movement series forming a pair. Only one pair was given per day and no other series of any kind were given on that day. Usually several days intervened between the II. test of one pair and the learning of the next, but in a little less than half of the cases a new pair was learned on the same day shortly after the II. test of the preceding pair.

The noun-object pairs and the verb-movement pairs were not given in any definite order with reference to each other.

The figures in the following table indicate the number of words out of ten which the subject correctly recalled and placed in their proper columns. Immediate recall is also given.

TABLE VII.

Series. Im. Rec. Two Days. Im. Rec. Two Days.
N. O. N. O. V. M. V. M.

_M._
D^{1-4} 8 9 7 7 7 10 4 5
D^{5-8} 9 7 6 6 8 8 6 6
D^{9-12} 7 7 5 6 8 10 7 7
Av. 24 23 18 19 23 28 17 17

_Mo_.
D^{1-4} 6 6 2 1 8 10 0¹ 7¹
D^{5-8} 6 5 0¹ 3¹ 8 9 2 4
D^{9-12} 5 7 1¹ 6¹ 10 10 2 7
Av. 17 18 3 10 26 29 4 18

_S_.
D^{1-4} 8 9 2 3 9 10 6¹ 9¹
D^{5-8} 8 10 2 4 9 10 4¹ 9¹
D^{9-12} 8 10 2 5 8 10 3¹ 7¹
Av. 24 29 6 12 26 30 13 25

_Hu._
D^{1-4} 6 8 3 7 9 10 4 9
D^{5-8} 7 9 0 2 9 10 2 7
D^{9-12} 7 9 4 6 8 10 1 8
Av. 20 26 7 15 26 30 7 24

_Ho._
D^{1-4} 9 9 3 3 10 9 5 7
D^{5-8} 9 8 1 6 9 9 6¹ 8¹
D^{9-12} 8 8 5 5 10 10 6¹ 7¹
Av. 26 25 9 14 29 28 17 22

¹ One day.

The results of the _D_ set strongly confirm the results of the _A_, _B_, and _C_ sets. Table VII. shows that after from one to two days' interval four subjects recall objects better than nouns and movements better than verbs. One subject, _M._, shows no preference.

CONCLUSIONS.

We are now in a position to answer specifically the problem of this investigation. The results show: (1) that those five subjects who recall objects better than nouns (involving images) _when each occurs alone_, also recall objects better than nouns when each is recalled by means of an unfamiliar verbal symbol with which it has been coupled; (2) that the same is true of verbs and movements; (3) that these facts also receive confirmation on the negative side, viz.: the one subject who does not recall objects and movements better than nouns and verbs (involving images) _when they are used alone_, also does not recall them better _when they are recalled by means of foreign symbols_ with which they have been coupled.

MINOR QUESTIONS.

The problem proposed at the outset of the investigation having been answered, two minor questions remain: (1) as to images, (2) indirect associations.

1. All the subjects were good visualizers. The images became clear usually during the first of the three presentations, _i.e._, in 1-3 secs., and persisted until the next couplet appeared. In the second and third presentations the same images recurred, rarely a new one appeared.

An interesting side light is thrown on M.'s memory by his work in another experiment in which he was a subject. This experiment required that the subject look at an object for 10 secs. and then after the disappearance of its after-image manipulate the memory image. M. showed unusually persistent after-images. The memory images which followed were unusually clear in details and also persistent. They were moreover retained for weeks, as was shown by his surprising ability to recall the details of an image long past, and separated from the present one by many subsequent images. His memory was capacious rather than selective. His eyesight was tested and found to be normal for the range of the apparatus. Possibly his age (55 yrs.) is significant, although one of the two subjects who showed the greatest preference for objects and movements, Mo., was only six yrs. younger. The ages of the other subjects were S. 36 yrs., Hu. 23 yrs., B. 25 yrs., Ho. 27 yrs.

That some if not all of the subjects did not have objective images in many of the noun and verb couplets if they were left to their own initiative to obtain them is evident from the image records in the _A_ set, in which the presence of the objective images was optional but the record obligatory. The same subject might have in one noun or verb series no visual images and in another he might have one for every couplet of the series. After the completion of the _A_ set, the effect of the presence of the objective images in series of 10 nouns alone, or 10 objects alone after two days' interval, was tested. This was merely a repetition of similar work by Kirkpatrick after three days' interval, and yielded similar results. As a matter of fact some of the subjects were unable wholly to exclude the objective images, but were compelled to admit and then suppress them as far as possible, so that it is really a question of degree of prominence and duration of the images.

The presence of the objective images having been shown to be an aid in the case of series of nouns, the subjects were henceforth requested to obtain them in the noun and verb series of the _B_ and _C_ sets, and the image records show that they were entirely successful in doing so.

2. The total number of couplets in any one or in several sets may be divided into two classes: (1) Those in which indirect associations did not occur in the learning, and (2) those in which they did occur. For reasons already named we may call the first pure material and the second mixed. We can then ascertain in each the proportion of correctly recalled couplets after one, two, nine and sixteen days' interval, and thus see the importance of indirect associations as a factor in recall. This is what has been done in the following table.

The figures give the number of couplets correctly or incorrectly recalled out of 64. In the case of the interval of one day the figures are a tabulation of the III. test (twenty-one hours) of the _C_ set, which contained 16 series of 4 couplets each. The figures for the intervals of two, nine and sixteen days are a tabulation of the _B_ set, which also contained 16 series of 4 couplets each. _C_ denotes correct, _I_ incorrect.

TABLE VIII.

SHOWING GREATER PERMANENCE OF COUPLETS IN WHICH INDIRECT ASSOCIATIONS OCCURRED.

Pure Material. Mixed Material.
Days. One. Two. Nine. Sixteen. One. Two. Nine. Sixteen.
C I C I C I C I C I C I C I C I
_M._ 40 22 23 39 22 40 2 0 2 0 3 0
_Mo._ 36 22 31 27 29 29 6 0 6 0 5 1
_S._ 27 34 6 55 2 59 1 60 2 1 3 0 3 0 3 0
_Hu._ 35 22 16 45 5 56 4 57 6 1 3 0 3 0 3 0
_B._ 48 16 17 43 9 51 7 53 0 0 4 0 1 3 1 3
_Ho._ 37 15 17 30 13 36 3 46 10 2 9 6 8 7 7 8

Total: 147 87 132 217 83 268 66 285 18 4 27 6 23 10 21 12
P'c't.: 63 37 38 62 24 76 19 81 82 18 82 18 70 30 64 36

We see from the table that the likelihood of recalling couplets in which indirect associations did not occur in learning is 63 per cent. after one day, and that there is a diminution of 44 per cent. in the next fifteen days. The fall is greatest during the second day. On the other hand, the likelihood of recalling couplets in which indirect associations did occur is 82 per cent. after one day, and there is a diminution of only 18 per cent. during the next fifteen days. The fading is also much more gradual.

It is evident, then, that in all investigations dealing with language material the factor of indirect associations--a largely accidental factor affecting varying amounts of the total material (in these six subjects from 3 per cent. to 23 per cent.) is by far the most influential of all the factors, and any investigations which have heretofore failed to isolate it are not conclusive as to other factors.

The practical value of the foregoing investigation will be found in its bearing upon the acquisition of language. While it is by no means confined to the acquisition of the vocabulary of a _foreign_ language, but is also applicable to the acquisition of the vocabulary of the native language, it is the former bearing which is perhaps more obvious. If it is important that one become able as speedily as possible to grasp the meaning of foreign words, the results of the foregoing investigation indicate the method one should adopt.

* * * * *

MUTUAL INHIBITION OF MEMORY IMAGES.

BY FREDERICK MEAKIN.

The results here presented are the record of a preliminary inquiry rather than a definitive statement of principles.

The effort to construct a satisfactory theory of inhibition has given rise, in recent years, to a good deal of discussion. Ever since it was discovered that the reflexes of the spinal cord are normally modified or restrained by the activity of the brain and Setschenow (1863) attempted to prove the existence of localized inhibition centers, the need of such a theory has been felt. The discussion, however, has been mainly physiological, and we cannot undertake to follow it here. The psychologist may not be indifferent, of course, to any comprehensive theory of nervous action. He works, indeed, under a general presumption which takes for granted a constant and definite relation between psychical and cerebral processes. But pending the settlement of the physiological question he may still continue with the study of facts to which general expression may be given under some theory of psychical inhibition not inconsistent with the findings of the physiologist.

A question of definition, however, confronts us here. Can we, it may be asked, speak of psychical inhibition at all? Does one conscious state exercise pressure on another, either to induce it, or to expel it from the field? 'Force' and 'pressure,' however pertinent to physical inquiries, are surely out of place in an investigation of the relations between the phenomena of mind. Plainly a distinction has to be made if we are to carry over the concept of inhibition from the domain of nervous activity to the conscious domain. Inhibition cannot, it should seem, have the same sense in both. We find, accordingly, that Baldwin, who defines nervous inhibition as 'interference with the normal result of a nervous excitement by an opposing force,' says of mental inhibition that it 'exists in so far as the occurrence of a mental process prevents the simultaneous occurrence of other mental processes which might otherwise take place.'[1]

[1] Baldwin, J.M.: 'Dictionary of Philosophy and Psychology,'
New York and London, 1901, Vol. I., article on 'Inhibition.'

Even here, it may be said, there is in the term 'prevents' an implication of the direct exercise of force. But if we abstract from any such implication, and conceive of such force as the term inhibition seems to connote, as restricted to the associated neural or physiological processes, no unwarranted assumptions need be imported by the term into the facts, and the definition may, perhaps, suffice.

Some careful work has been done in the general field of psychical inhibition. In fact, the question of inhibition could hardly be avoided in any inquiry concerning attention or volition. A. Binet[2] reports certain experiments in regard to the rivalry of conscious states. But the states considered were more properly those of attention and volition than of mere ideation. And the same author reports later[3] examples of antagonism between images and sensations, showing how the latter may be affected, and in some respects inhibited, by the former. But this is inhibition of sensations rather than of ideas. Again, Binet, in collaboration with Victor Henri,[4] reports certain inhibitory effects produced in the phenomena of speech. But here again the material studied was volitional. More recently, G. Heymans[5] has made elaborate investigation of a certain phase of 'psychische Hemmung,' and showed how the threshold of perception may be raised, for the various special senses, by the interaction of rival sensations, justly contending that this shifting of the threshold measures the degree in which the original sensation is inhibited by its rival. But the field of inquiry was in that case strictly sensational. We find also a discussion by Robert Saxinger,[6] 'Ueber den Einfluss der Gefühle auf die Vorstellungsbewegung.' But the treatment there, aside from the fact that it deals with the emotions, is theoretical rather than experimental.

[2] Binet, A.: _Revue Philosophique_, 1890, XXIX., p. 138.

[3] Binet, A.: _Revue Philosophique_, 1890, XXX., p. 136.

[4] Binet, A., et Henri, V.: _Revue Philosophique_, 1894,
XXXVII., p. 608.

[5] Heymans, G.: _Zeitschrift f. Psych. u. Physiol. d.
Sinnesorgane_, 1899, Bd. XXI., S. 321; _Ibid._, 1901, Bd.
XXVI., S. 305.

[6] Saxinger, R.: _Zeitschrift f. Psych. u. Physiol. d.
Sinnesorgane_, 1901, Bd. XXVI., S. 18.

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 passively 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 associated 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 attitude required of the observer was one which is not commonly taken. And it may be objected that the results of an attitude 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 attitude not easy to assume. 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.

_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 assumption 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 assumed 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 quantitative 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 space 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 attitude of the subject towards his image seems to have been much the same as his attitude 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 mass; 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 'mass' 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."

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 associated 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 associated 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 assume 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 attitude 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 attitude and may be incipient merely, but which, if completed, result in the shifting of the eyes and the changes of bodily attitude 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. Münsterberg, H.: 'Grundzüge 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 attitude 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 assume, 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 assumes a place in consciousness which but for itself, as experiment indicates, another might occupy, inhibits the other.

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

313 392 254 353.5 292.5 381.5 290 386 293.5 388.5 255 375.5

7 8 9 10 Averages
S L S L S L S L S L
I. 20.5 31.5 21.5 28.5 22.5 28 22.5 26 20.90 26.50
II. 14.5 17.5 19 20 11 4.5 7 30.5 16.10 25.00
III. 10 22 8.5 26 17 16 8 16 12.35 21.90
IV. 27.5 28.5 35 30.5 23.5 46 27.5 49.5 28.95 33.35
V. 40.5 35 24.5 22.5 21 31 21.5 21.5 35.40 36.75
VI. 22.5 18.5 11.5 21 20 27 22.5 24 21.35 21.60
VII. 44.5 46.5 52 51 33.5 49 39.5 50.5 44.85 47.85
VIII. 19.5 20 21 27 19.5 27.5 18.5 22.5 24.05 29.60
IX. 18.5 46 13 42 20 42 18.5 43 19.95 44.90
X. 18.5 24 20.5 21 20.5 22 18.5 28.5 17.00 28.75
XI. 21 49 32 53.5 38 53.5 34.5 46.5 29.00 50.15

257.5 338.5 258.5 343 246.5 346.5 238.5 358.5 24.54 33.30

_L_: large. _S_: small.

General average, _S_, 24.54 sec.; _L_, 33.30 sec.

_Series No. III._--In the third series, where the variant is the extent of (gray) surface exposed, the preponderance is in favor of the image corresponding to the larger object. This shows an appearance of some 33 seconds per minute as against 24 for the smaller (Table III.). Here the most obvious thing in the reports, aside from the relative durations, is the greater vividness of the favored image. Something, no doubt, is due to the greater length of boundary line and other spatial dimensions involved in the greater size. And it is this superiority, and the ampler movements which it implies, which were probably felt by the subject who reports 'a feeling of expansion in the eye which corresponds to the larger image and of contraction in the other.' But the more general comment is as to the greater vividness of the larger image. "The larger images seem brighter whichever side they are on." "The larger is a little more distinct, as if it were nearer to me." "Large much more vivid than small." Such are the reports which run through the series. And they point, undoubtedly, to a cumulative effect, corresponding to a well-known effect in sensation, in virtue of which greater extension may become the equivalent of greater intensity. In other words, the larger image made the stronger impression. Now in external perception the stronger impression tends to hold the attention more securely; that is, it is more effective in producing those adjustments of the sensory organs which perceptive attention implies. So here what was noticed as the superior brightness and distinctness of the larger image may be supposed to imply some advantage in the latter in securing those adjustments of the mental attitude which were favorable to the apprehension of that image. Advantage means here, again, in part at least, if the considerations we have urged are sound, inhibition of those motor processes which would tend to turn attention to a rival. And here, again, the adjustment may reach no external organ. An incipient innervation, which is all that we need assume as the condition of a change of mental attitude, would suffice to block, or at least to hamper, inconsistent innervations no more complete than itself.

TABLE IV.

1 2 3 4
G W G W G W G W
I. 15.5 28.5 21.5 32.5 20 33 21 28.5
II. 39.5 23 22.5 22.5 19 20.5 35.5 17.5
III. 13.5 12.5 32 4.5 8.5 10 11.5 11.5
IV. 30 33.5 38 36.5 36 39.5 37.5 13.5
V. 33.5 32.5 34.5 32 33 35 45 36.5
VI. 15 22 21 21 18.5 22 12 22
VII. 53.5 50 43 46 54.5 55 56 56
VIII. 15.5 24.5 24 25 20 13 16.5 21
IX. 17.5 44 9.5 46 18.5 43.5 16 42
X. 25.5 19 29.5 19 21 20.5 23.5 18
XI. 35 42.5 13 29.5 18.5 46 16 38
294 332 288.5 314.5 267.5 338 290.5 304.5

5 6 7 8
G W G W G W G W
I. 24 26.5 23.5 25 19.5 30.5 21 29
II. 21 29.5 20 18.5 29 16.5 28.5 14
III. 20.5 8.5 11 11.5 10 14 23 16.5
IV. 39.5 28.5 34.5 22.5 23 30.5 33.5 18
V. 45 53 48 51 45 29 32.5 34.5
VI. 21.5 28 18 32 20.5 19 21.5 18
VII. 54.5 56 54.5 54.5 45 46 49 49
VIII. 24 26.5 23.5 22.5 24 17.5 31 31.5
IX. 16 44 14 43.5 9 43.5 13 44.5
X. 24.5 18 24 21.5 25.5 24 22 22.5
XI. 20.5 8.5 15 36.5 33 23 34 29
311 327 286 339 283.5 293.5 309 306.5