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.