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.