How We Experiment on the Mind : Part 4

The Story of the Mind
by James Mark Baldwin

(Page 9 of 15)

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 traveling 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 millimeters the exact point at which the needle stops, releases the needle by breaking the current, therefore 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.

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 (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 genders, 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, 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.

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 esthetics. 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 masses 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 principal laws of esthetic 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 masses 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 illustrate 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. 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.

The first experiments were made by Messrs. S. and B. in the University of Toronto on a class of students numbering nearly three hundred, of whom about one third were women. The instructors showed to the class 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 (illustrating 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).

Copyright 1902 by D. Appleton and Company.

About the Author

James Mark Baldwin (1861-1934) was an American philosopher and psychologist who was educated at Princeton under the supervision of Scottish philosopher James McCosh. He made important contributions to early psychology, psychiatry, and to the theory of evolution.