The Story of the Mind

by James Mark Baldwin

The general results will show, therefore, if they should be confirmed by other investigators, that our temperature sense is located in what might be called somewhat large blotches on the skin, and not in minute spots; while the evidence still remains good, however, to show that we have two senses for temperature, one for cold and the other for hot.

II. Reaction-Time Experiments.—Work in so-called "reaction times" constitutes one of the most important and well-developed chapters in experimental psychology. In brief, the experiment involved is this: To find how long it takes a person to receive a sense impression of any kind—for example, to hear a sound-signal—and to move his hand or other member in response to the impression. A simple arrangement is as follows: Sit the subject comfortably, tap a bell in such a way that the tapping also makes an electric current and starts a clock, and instruct the subject to press a button with his finger as soon as possible after he hears the bell. The pressing of the button by him breaks the current and stops the clock. The dial of the clock indicates the actual time which has elapsed between the bell (signal) and his response with his finger (reaction). The clock used for exact work is likely to be the Hipp chronoscope, which gives on its dials indications of time intervals in thousandths of a second. For the sake of keeping the conditions constant and preventing disturbance, the wires are made long, so that the clock and the experimenter may be in one room, while the bell, the punch key, and the subject are in another, with the door closed. This method of getting reaction times has been in use for a number of years, especially by the astronomers who need to know, in making their observations, how much time is taken by the observer in recording a transit or other observation. It is part of the astronomer's "personal equation."

Proceeding with this "simple-reaction" experiment as a basis, the psychologists have varied the instructions to the subject so as to secure from him the different times which he takes for more complicated mental processes, such as distinguishing between two or more impressions, counting, multiplying, dividing, etc., before reacting; or they have him wait for an associated idea to come up before giving his response, with many other variations. By comparing these different times among themselves, interesting results are reached concerning the mental processes involved and also about the differences of different individuals in the simpler operations of their daily lives. The following research carried out by Mr. B.[4] serves to illustrate both of these assertions.

[4] The writer.

Mr. B. wished to inquire further into a fact found out by several persons by this method: the fact that there is an important difference in the length of a person's reaction time according to the direction of his attention during the experiment. If, for example, Mr. X. be tested, it is possible that he may prefer to attend strictly to the signal, letting his finger push the key without direct care and supervision. If this be true, and we then interfere with his way of proceeding, by telling him that he must attend to his finger, and allow the signal to take care of itself, we find that he has great difficulty in doing so, grows embarrassed, and his reaction time becomes very irregular and much longer. Yet another person, say Y, may show just the opposite state of things; he finds it easier to pay attention to his hand, and when he does so he gets shorter and also more regular times than when he attends to the signal-sound.

It occurred to Mr. B. that the striking differences given by different persons in this matter of the most favourable direction of the attention might be connected with the facts brought out by the physiological psychologists in connection with speech; namely, that one person is a "visual," in speaking, using mainly sight images of words, while another is a "motor," using mainly muscular images, and yet another an "auditive," using mainly sound images. If the differences are so marked in the matter of speech, it seemed likely that they might also extend to other functions, and the so-called "type" of a person in his speech might show itself in the relative lengths of his reaction times according as he attended to one class of images or another.

Calling this the "type theory" of reaction times, and setting about testing four different persons in the laboratory, the problem was divided into two parts; first, to direct all the individuals selected to find out, by examining their mental preferences in speaking, reading, writing, dreaming, etc., the class of images which they ordinarily depended most upon; and then to see by a series of experiments whether their reaction times to these particular classes of images were shorter than to others, and especially whether the times were shorter when attention was given to these images than when it was given to the muscles used in the reactions. The meaning of this would be that if the reaction should be shorter to these images than to the corresponding muscle images, or to the other classes of images, then the reaction time of an individual would show his mental type and be of use in testing it. This would be a very important matter if it should hold, seeing that many questions both in medicine and in education, which involve the ascertaining of the mental character of the individual person, would profit by such an exact method.

The results on all the subjects confirmed the supposition. For example, one of them, Mr. C., found from an independent examination of himself, most carefully made, that he depended very largely upon his hearing in all the functions mentioned. When he thought of words, he remembered how they sounded; when he dreamed, his dreams were full of conversation and other sounds. When he wrote, he thought continually of the way the words and sentences would sound if spoken. Without knowing of this, many series of reaction experiments were made on him; the result showed a remarkable difference between the lengths of his reactions, according as he directed his attention to the sound or to his hand; a difference showing his time to be one half shorter when he paid attention to the sound. The same was seen when he reacted to lights; the attention went preferably to the light, not to the hand; but the difference was less than in the case of sounds. So it was an unmistakable fact in his case that the results of the reaction experiments agreed with his independent decision as to his mental type.

In none of the cases did this correspondence fail, although all were not so pronounced in their type preferences as was Mr. C.

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).