The Story of the Mind

by James Mark Baldwin

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 class 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 embarrassment, and the direction of best progress in education.

This research may be taken to illustrate 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 Æsthetics, 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 Assimilation, which has already been remarked upon. In the latter case it illustrates 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 illustrated 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. Wishing 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 passed, 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.