572 THE POPULAR SCIENCE MONTHLY. 



the signal was to be given with the right hand, for a white light with 

 the left hand. In this case the mental action of deciding these alter- 

 natives and coordinating the corresponding act of volition required 

 no less than .154, or nearly one-seventh of a second. 



Other experiments have been made with the sense of sight, where 

 the patient was instructed to give the signal by pronouncing the name 

 of a vowel which was shown to him. If he had to distinguish between 

 two vowels, the psychical time was prolonged .166 of a second beyond 

 what it would have been for one vowel. If he was required to name 

 one out of five, the prolongation was increased to .ITO of a second. 



Similar experiments with the sense of hearing, where the vowel 

 was spoken to the patient and repeated by him, gave similar results. 

 Where two vowels were selected from the mind occupied .056, and 

 where five were used .086 of a second longer than if only one expected 

 vowel were spoken. 



Where two colors were shown, and the signal was given by a 

 movement of the hand, or by the voice, the physiological time for the 

 movement of the hand was found to be always greater than for the 

 voice. 



When the signal was the pronouncing of a vowel, as " i," the time 

 required was less than when the patient was obliged to speak the 

 vowel with a consonant before it, as " pi," or " ki," or " ti." The let- 

 ter " p " was found to retard the patient .011 of a second, " t " twice as 

 lonsr, or .022 of a second, and " k " .021 of a second. A further result of 

 these curious investigations was that the patient required three times 

 as long to distinguish between two letters which were shown upon a 

 screen as to distinguish between the two corresponding vowels when 

 spoken. 



In all these investigations the psychical time is made up of two 

 periods : the first required by the mind to perceive the sensation or 

 to distinguish the alternative, the second required for the mental act 

 of willing the signal. An attempt has been made to measure each of 

 these. The experiment for this purpose was so arranged that the pa- 

 tient was to hear several vowels,,but was directed to give the signal 

 only upon hearing a certain one of them. Under this arrangement 

 the patient concentrated his attention upon the perception of the 

 vowel at hearing which he was to act. He prepared himself, as 

 far as could be, to pronounce it the moment he heard it. Before he 

 heard it he willed to speak it on the instant that he should perceive 

 it. There remained only the act of recognizing the vowel when it 

 should be spoken, of distinguishing it among the other vowels. The 

 act of volition was in this way eliminated from the physiological time, 

 and the simplest mental act of distinguishing was calculated from the 

 result. This result, based upon this and similar experiments, was that 

 the mental act of distinguishing reqviired about one twenty-third of a 

 second of time. The whole psychical time being about one-twelfth 



