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). [Illustration: 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.