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.