The Story of the Mind Part 7

The second part of the research had in view the question whether reaction times taken upon speech would show the same thing; that is, whether in Mr. C.'s case, for example, it would be found that his reaction made by speaking, as soon as he heard the signal or saw the light, would be shorter when he paid attention to the signal than when he gave attention to his mouth and lips. For this purpose a mouth key was used which made it possible for the subject simply by emitting a puff of breath from the lips, to break an electric current and thus stop the chronoscope as soon as possible after hearing the signal.

The mouth key is figured herewith (Fig. 6).

[Ill.u.s.tration: FIG. 6.--Mouth-key (Isometric drawing) The metallic tongue E swings over the mercury H, making or breaking the circuit A H E D B or C E H A. The tongue is moved by a puff of air through the funnel F. (Devised by Prof. W. Libbey.)]

This experiment was also carried out on all the subjects, none of them having any knowledge of the end in view, and the experimenters also not having, as yet, worked out the results of the earlier research. In all the cases, again, the results showed that, for speech, the same thing held as for the hand--namely, that the shortest reaction times were secured when the subject paid attention to the cla.s.s of images for which he had a general preference. In Mr. C.'s case, for example, it was found that the time it took him to speak was much shorter when he paid strict attention to the expected sound than when he attended to his vocal organs. So for the other cases. If the individual's general preference is for muscular images, we find that the quickest time is made when attention is given to the mouth and lips. Such is the case with Mr. B.

The general results go to show, therefore--and four cases showing no exception, added to the indications found by other writers, make a general conclusion very probable--that in the differences in reaction times, as secured by giving the attention this way or that, we have general indications of the individual's temperament, or at least of his mental preferences as set by his education. These indications agree with those found in the cases of aphasia known as "motor,"

"visual," "auditory," etc., already mentioned. The early examination of children by this method would probably be of great service in determining proper courses of treatment, subjects of study, modes of discipline, tendencies to fatigue and embarra.s.sment, and the direction of best progress in education.

This research may be taken to ill.u.s.trate the use of the reaction-time method in investigating such complex processes as attention, temperament, etc. The department which includes the various time measurements in psychology is now called Mental Chronometry, the older term, Psychometry, being less used on account of its ambiguity.

III. _An Optical Illusion._--In the sphere of vision many very interesting facts are constantly coming to light. Sight is the most complex of the senses, the most easily deranged, and, withal, the most necessary to our normal existence. The report of the following experimental study will have the greater utility, since, apart from any intrinsic novelty or importance the results may prove to have, it shows some of the general bearings of the facts of vision in relation to aesthetics, to the theory of Illusions, and to the function of Judgment.

Illusion of the senses is due either to purely physiological causes or to the operation of the principle of a.s.similation, which has already been remarked upon. In the latter case it ill.u.s.trates the fact that at any time there is a general disposition of the mind to look upon a thing under certain forms, patterns, etc., to which it has grown accustomed; and to do this it is led sometimes to distort what it sees or hears unconsciously to itself. So it falls into errors of judgment through the trap which is set by its own manner of working. Nowhere is the matter better ill.u.s.trated than in the sphere of vision. The number of illusions of vision is remarkable. We are constantly taking shapes and forms for something slightly different from what, by measurement, we actually find them to be. And psychologists are attempting--with rather poor success so far--to find some general principles of the mechanism of vision which will account for the great variety of its illusions.

Among these principles one is known as Contrast. It is hardly a principle as yet. It is rather a word used to cover all illusions which spring up when surfaces of different sizes and shapes, looked at together or successively, are misjudged with reference to one another.

Wis.h.i.+ng to investigate this in a simple way, the following experiment was planned and carried out by Mr. B.

He wished to find out whether, if two detached surfaces of different sizes be gazed at together, the linear distances of the field of vision (the whole scene visible at once) would be at all misjudged. To test this, he put in the window (W)[5] of the dark room a filling of white cardboard in which two square holes had been cut (S S'). The sides of the squares were of certain very unequal lengths. Then a slit was made between the middle points of the sides of the squares next to each other, so that there was a narrow path or trough joining the squares between their adjacent sides. Inside the dark room he arranged a bright light so that it would illuminate this trough, but not be seen by a person seated some distance in front of the window in the next room. A needle (D) was hung on a pivot behind the cardboard, so that its point could move along the bright trough in either direction; and on the needle was put the armature (A) of an electro-magnet which, when a current pa.s.sed, would be drawn instantly to the magnet (E), and so stop the needle exactly at the point which it had then reached. A clock motor (Cm) was arranged in such a way as to carry the needle back and forth regularly over the slit; and the electro-magnet was connected by wires with a punch key (K) on a table beside the subject in the next room. All being now ready, the subject, Mr. S., is told to watch the needle which appears as a bead of light travelling along the slit, and stop it when it comes to the middle point of the line, by pressing the electric key. The experimenter, who stands behind the window in the dark room, reads on a scale (mm.) marked in millimetres the exact point at which the needle stops, releases the needle by breaking the current, thus allowing it to return slowly over the line again. This gives the subject another opportunity to stop it at what he judges to be the exact middle of the line, and so on. The accompanying figure (Fig. 7) shows the entire arrangement.

[Footnote 5: This and the following letters in parentheses refer to Fig. 7]

[Ill.u.s.tration: FIG. 7]

A great many experiments performed in this way, with the squares set both vertically and horizontally, and with several persons, brought a striking and very uniform result. The point selected by the subject as the middle is regularly too far toward the smaller square. Not a little, indeed, but a very appreciable amount. The amount of the displacement, or, roughly speaking, of the illusion, increases as the larger square is made larger and the smaller one smaller; or, put in a sentence, the amount varies directly with the ratio of the smaller to the larger square side.

Finding such an unmistakable illusion by this method, Mr. B. thought that if it could be tested by an appeal to people generally, it would be of great gain. It occurred to him that the way to do this would be to reverse the conditions of the experiment in the following way: He prepared the figures given in Plate I, in which the two squares are made of suitable relative size, a line is drawn between them, and a point on the line is plainly marked. This he had printed in a weekly journal, and asked the readers of the journal to get their friends, after merely looking at the figure (i. e., without knowing the result to be expected), to say--as the reader may now do before reading further--whether the point on the line (Plate I) is in the middle or not; and if not, in which direction from the true middle it lies. The results from hundreds of persons of all manner of occupations, ages, and of both s.e.xes, agree in saying that the point lies too far toward the larger square. In reality it is in the exact middle. This is just the opposite of the result of the experiments in the laboratory, where the conditions were the reverse, i. e., to find the middle as it appears to the eye. Here, therefore, we have a complete confirmation of the illusion; and it is now fully established that in all cases in which the conditions of this experiment are realized we make a constant mistake in estimating distances by the eye.[6]

[Footnote 6: In redrawing the figure on a larger sheet (which is recommended), the connecting line may be omitted, only the mid-point being marked. Some get a better effect with two circles, the intervening distance being divided midway by a dot, as in Plate II.]

For instance, if a town committee wish to erect a statue to their local hero in the public square, and if on two opposite sides of the square there are buildings of very different heights, the statue should not be put in the exact middle of the square, if it is to give the best effect from a distance. It should be placed a little toward the smaller building. A colleague of the writer found, when this was first made public, that the pictures in his house had actually been hung in such a way as to allow for this illusion. Whenever a picture was to be put up between two others of considerable difference of size, or between a door (large) and a window (small), it had actually been hung a little nearer to the smaller--toward the small picture or toward the window--and not in the true middle.

It is probable that interesting applications of this illusion may be discovered in aesthetics. For wherever in drawing or painting it is wished to indicate to the observer that a point is midway between two lines of different lengths, we should find that the artist, in order to produce this effect most adequately, deviates a little from the true middle. So in architecture, the effect of a contrast of ma.s.ses often depends upon the sense of bilateral balance, symmetry, or equality, in which this visual error would naturally come into play.

Indeed, it is only necessary to recall to mind that one of the princ.i.p.al laws of aesthetic effect in the matter of right line proportion is the relation of "one to one," as it is called, or equal division, to see the wide sphere of application of this illusion. In all such cases the mistake of judgment would have to be allowed for if ma.s.ses of unequal size lie at the ends of the line which is to be divided.

IV. _The Accuracy of Memory._--Another investigation may be cited to ill.u.s.trate quite a different department. It aimed to find out something about the rate at which memory fades with the lapse of time.

Messrs. W., S., and B.[7] began by formulating the different ways in which tests may be made on individuals to see how accurate their memories are after different periods of time. They found that three different tests might be employed, and called them "methods" of investigating memory. These are, first, the method of Reproduction.

The individual is asked to reproduce, as in an oral or written examination, what he remembers of something told him a certain time before. This is the ordinary method of the schools and colleges, of civil-service examinations, etc. Second, the method of Identification, which calls upon the person to identify a thing, sentence, report, etc., a second or third time, as being the same in all respects as that which he experienced the first time it appeared. Third, the method of Selection, in which we show to the person a number of things, sentences, reports, descriptions of objects, etc., and require him to select from them the ones which are exactly the same as those he has had before. These methods will be better understood from the account now to be given of the way they were carried out on a large number of students.

[Footnote 7: Prof. H. C. Warren, Mr. W. J. Shaw, and the writer.]

The first experiments were made by Messrs. S. and B. in the University of Toronto on a cla.s.s of students numbering nearly three hundred, of whom about one third were women. The instructors showed to the cla.s.s certain squares of cardboard of suitable size, and asked them to do the following three things on different days: First, to reproduce from memory, with pencil on paper, squares of the same size as those shown, after intervals of one, ten, twenty, and forty minutes (this gives results by the method of Reproduction); second, to say whether a new set of squares, which were shown to them after the same intervals, were the same in size as those which they had originally seen, smaller, or larger (ill.u.s.trating the method of Identification); third, they were shown a number of squares of slightly different sizes, again at the same intervals, and asked to select from them the ones which they found to be the same size as those originally seen (method of Selection).

The results from all these experiments were combined with those of another series, secured from a large cla.s.s of Princeton students; and the figure (Fig. 8) shows by curves something of the result. The figure is given in order that the reader may understand by its explanation the "graphic method" of plotting statistical results, which, with various complications, is now employed in psychology as well as in the other positive sciences.

[Ill.u.s.tration: FIG. 8.--Memory curves: I. Method of Selection. II.

Method of Identification.]

Briefly described in words, it was found that the three methods agreed (the curves are parallel)[8] in showing that during the first ten minutes there was a great falling off in the accuracy of memory (slant in the curves from 0 to 10); that then, between ten and twenty minutes, memory remained relatively faithful (the curves are nearly level from 10 to 20), and that a rapid falling off in accuracy occurred after twenty minutes (shown by the slant in the lines from 20 to 40).

[Footnote 8: This figure shows curves for two of the methods only, Selection and Identification.]

Further, the different positions of the curves show certain things when properly understood. The curve secured by the method of Reproduction (not given in the figure) shows results which are least accurate, because most variable. The reason of this is that in drawing the squares to reproduce the one remembered, the student is influenced by the size of the paper he uses, by the varying accuracy of his control over his hand and arm (the results vary, for example, according as he uses his right or left hand), and by all sorts of a.s.sociations with square objects which may at the time be in his mind.

In short, this method gives his memory of the square a chance to be fully a.s.similated to his current mental state during the interval, and there is no corrective outside of him to keep him true.

That this difficulty is a real one no one who has examined students will be disposed to deny. When we ask them to reproduce what the text-book or the professor's lectures have taught, we also ask them to express themselves accurately. Now the science of correct expression is a thing in which the average student has had no training. With his difficulty in remembering is connected his difficulty of expression; and with it all goes a certain embarra.s.sment, due to responsibility, personal fear, and dread of disgrace. So the results finally obtained by this method are really very complex.

One of the curves, that given by the method of Selection (I), also shows memory to be interfered with by a certain influence. We saw in connection with the experiments reported above that, even in the most elementary arrangements of squares in the visual fields, an element of contrast comes in to interfere with our judgment of size. This we find confirmed in these experiments when the method of Selection is used.

By this method we show a number of squares side by side, asking the individual to select the one he saw before. All the squares, being shown at once, come into contrast with one another on the background; and so his judgment of the size of the one he remembers is distorted.

This, again, is a real influence in our mental lives, leading to actual illusion. An unscrupulous lawyer may gradually modify the story which his client or a witness tells by constantly adding to what is really remembered, other details so expertly contrasted with the facts, or so neatly interposed among them, that the witness gradually incorporates them in his memory and so testifies more nearly as the lawyer desires. In our daily lives another element of contrast is also very strong--that due to social opinion. We constantly modify our memories to agree more closely with the truths of social belief, paring down unconsciously the difference between our own and others'

reports of things. If several witnesses of an event be allowed to compare notes from time to time, they will gradually come to tell more nearly the same story.

The other curve (II) in the figure, that secured by the method of Identification, seemed to the investigators to be the most accurate.

It is not subject to the errors due to expression and to contrast, and it has the advantage of allowing the subject the right to recognise the square. It is shown to him again, with no information that it is the same, and he decides whether from his remembrance of the earlier one, it is the same or not. The only objection to this method is that it requires a great many experiments in order to get an average result. To be reliable, an average must be secured, seeing that, for one or two or a few trials, the student may guess right without remembering the original square at all. By taking a large number of persons, such as the three hundred students, this objection may be overcome. Comparing the averages, for example, of the results given by the men and women respectively, we found practically no difference between them.

This last point may serve to introduce a distinction which is important in all work in experimental psychology, and one which is recognised also in many other sciences--the distinction between results obtained respectively from one individual and from many. Very often the only way to learn truth about a single individual is to investigate a number together. In all large cla.s.ses of things, especially living things, there are great individual differences, and in any particular case this personal variation may be so large that it obscures the real nature of the normal. For example, three large sons may be born to two small parents; and from this case alone it might be inferred that all small parents have large sons. Or three girls might have better memories than three boys in the same family or school, and from this it might be argued that girls are better endowed in this direction than boys. In all such cases the proper thing to do is to get a large number of cases and combine them; then the preponderance which the first cases examined may have shown, in one direction or the other, is corrected. This gives rise to what is called the statistical method; it is used in many practical matters, such as life insurance, but its application to the facts of life, mind, variation, evolution, etc., is only begun. Its neglect in psychology is one of the crying defects of much recent work. Its use in complicated problems involves a mathematical training which people generally do not possess; and its misuse through lack of exactness of observation or ignorance of the requirements is worse than its neglect.

Another result came out in connection with these experiments on memory, which, apart from its practical interest, may serve to show an additional resource of experimental psychology. In making up the results of a series of experiments it is very important to observe the way in which the different cases differ from one another. Some cases may be so nearly alike that the most extreme of them are not far from the average of them all; as we find, for example, if we measure a thousand No. 10 shot. But now suppose we mix in with the No. 10 some No. 6 and some No. 14, and then take the average size; we may now get just the same average, and we can tell that this pile is different from the other only by observing the individual measurements of the single shot and setting down the relative frequency of each particular size. Or, again, we may get a different average size in one of two ways: either by taking another lot of uniform No. 14 shot, let us say, or by mixing with the No. 10 a few very large bullets. Which is actually the case would be shown only by the examination of the individual cases. This is usually done by comparing each case with the average of the whole lot, and taking the average of the differences thus secured--a quant.i.ty called the "mean variation."

In the case of the experiments with the squares, the errors in the judgments of the students were found to lie always in one direction.

The answers all tended to show that they took, for the one originally shown, a square which was really too large. Casting about for the reason of this, it was considered necessary to explain it by the supposition that the square remembered had in the interval become enlarged in memory. The image was larger when called up after ten or twenty minutes than it was before. This might be due to a purely mental process; or possibly to a sort of spreading-out of the brain process in the visual centre, giving the result that whenever, by the revival of the brain process, the mental image is brought back again to mind, this spreading out shows itself by an enlargement of the memory image. However it may be explained, the indications of it were unmistakable--unless, of course, some other reason can be given for the uniform direction of the errors; and it is further seen in other experiments carried out by Messrs. W. and B. and by Dr. K.[9] at a later date.

[Footnote 9: Dr. F. Kennedy, demonstrator, now professor in the University of Colorado (results not yet published).]

If this tendency to the enlargement of our memories with the lapse of time should be found to be a general law of memory, it would have interesting bearings. It would suggest, for instance, an explanation of the familiar fact that the scenes of the past seem to us, when we return to them, altogether too small. Our childhood home, the old flower garden, the height of house and trees, and even that of our hero uncle, all seem to the returning traveller of adult life ridiculously small. That we expect them to be larger may result from the fact that the memory images have undergone change in the direction of enlargement.

V. _Suggestion._--s.p.a.ce permits only the mention of another research, which, however, should not be altogether omitted, since it ill.u.s.trates yet other problems and the principles of their solution. This is an investigation by Messrs. T. and H.,[10] which shows the remarkable influence of mental suggestions upon certain bodily processes which have always been considered purely physiological. These investigators set out to repeat certain experiments of others which showed that if two points, say those of a pair of compa.s.ses, be somewhat separated and put upon the skin, two sensations of contact come from the points.

But if while the experiment is being performed the points be brought constantly nearer to each other, a time arrives when the two are felt as only one, although they may be still some distance apart. The physiologists argued from this that there were minute nerve endings in the skin at least so far apart as the least distance at which the points were felt as two; and that when the points were so close together that they only touched one of these nerve endings, only one sensation was produced. Mr. T. had already found, working in Germany, that, with practice, the skin gradually became more and more able to discriminate the two points--that is, to feel the two at smaller distances; and, further, that the exercise of the skin in this way on one side of the body not only made that locality more sensitive to minute differences, but had the same effect, singularly, on the corresponding place on the other side of the body. This, our experimenters inferred, could only be due to the continued suggestion in the mind of the subject that he should feel two points, the result being an actual heightening of the sensibility of the skin. When he thought that he was becoming more sensitive on one side--and really was--this sense or belief of his took effect in some way in both hemispheres of his brain, and so both sides of the body were alike affected.

[Footnote 10: G. A. Tawney, now professor in Beloit College, and C. W.

Hodge, now professor in Lafayette College.]

This led to other experiments in Princeton in which suggestions were actually made to the subjects that they were to become more or less sensitive to distance and direction between the points on the skin, with the striking result that these suggestions actually took effect all over the body. This was so accurately determined that from the results of the experiments with the compa.s.ses on the skin in this case or that, pretty accurate inferences could be made as to what mental suggestions the subject was getting at the time. There was no chance for deception in the results, for the experiments were so controlled that the subject did not know until afterward of the correspondences actually reached between his states of mind and the variations in sensibility of the skin.

This slight report of the work done in one laboratory in about two sessions, involving a considerable variety of topics, may give an idea, so far as it goes, of the sort of work which experimental psychology is setting itself to do. It will be seen that there is as yet no well-knit body of results on which new experiments may proceed, and no developed set of experimental arrangements, such as other positive sciences show. The procedure is, in many important matters, still a matter of the individual worker's judgment and ability. Even for the demonstrations attempted for undergraduate students, good and cheap apparatus is still lacking. For these reasons it is premature as yet to expect that this branch of the science will cut much of a figure in education. There can be no doubt, however, that it is making many interesting contributions to our knowledge of the mind, and that when it is more adequately organized and developed in its methods and apparatus, It will become the basis of discipline of a certain kind lying between that of physical science and that of the humanities, since it will have features in common with the biological and natural sciences. Its results may be expected also to lead to better results than we now have in the theory and practice of education.

CHAPTER VII.

SUGGESTION IN CHILDREN AND ADULTS--HYPNOTISM.

In an earlier place certain ill.u.s.trations of Suggestion have been given. By Suggestion we mean the fact that all sorts of hints from without disturb and modify the beliefs and actions of the individual.

Certain cases from my own observation may be given which will make the matter clear.

_Physiological Suggestion._--Observation of an infant for the first month or six weeks after birth leads to the conviction that his life is mainly physiological. When the actions which are purely reflex, together with certain random impulsive movements, are noted, we seem to exhaust the case.