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 tha