Page:Mind (Old Series) Volume 11.djvu/236

 THE TIME TAKEN UP BY CEREBRAL OPERATIONS. 235 about y^-g-s. from those preceding and following it, and less than J-Q-^-S. from reactions made on different days and under changed circumstances. I do not however lay much weight on the third decimal ; if this investigation were to be repeated it is not likely that we should obtain the same results to Y^nj-<yS. When B's reaction-time for light is given as 1500-, I only mean that this was the result of these 520 reactions ; in comparing this with other determinations where we wish to know the absolute length of B's reaction-time, we can best limit ourselves to saying that it is '15s., or perhaps better still, between -14 and '16s. In these experiments the reaction was made with the right hand. The time is the same with the left hand. 1 I give in Table II. the average of five series (130 reactions) made with the left hand on light and also on sound. 2 TABLE II. I J C 1 R V R' V R V R' V Light... 3-7. IV 153 19 156 8 147 11 148 6 Sound... 3-7. IV 126 8 126 6 122 11 122 7 It is a matter which the later sections of this paper will show to be of special interest to us that the time is longer when the re- action is made with the speech-organs. To determine this time I used both the lip-key and the sound-key above described. In either case the observer said ' Jetzt ' as soon as possible after the appearance of the light, and the motion of the speech-organs stopped the hands of the chronoscope in the way I have explained. The results of these experiments are given in Table III. We thus find that it takes about 30<r longer to make the re- action with the speech- organs than with the hand. I used an additional method of determining the reaction-time with the speech- organs. The observer as quickly as possible after the appearance of the light simply said * Jetzt ' ; a second observer as soon as he heard the sound let go the telegraph-key, and this stopped the hands of the chronoscope. The hands recorded the time of a double reaction, that of the first observer on the light with his speech-organs, and that of the second observer on the sound with his hand. But we can determine 1 Tischer, Phil. Studien, i., 534 ; Merkel, Ib., ii., 88. Prof. G. S. Hall and Dr. Hartwell (MiND, ix. 93) do not seem to have known of the work published by Tischer and Merkel. 2 The sound (as in all cases where the reaction-time for sound was measured) was made by a stone ball 22 gr. in weight, falling from a height of 33 cm. on the wooden base of the Hipp gravity-apparatus.