Page:Mind (Old Series) Volume 11.djvu/537

536 J. M. CATTELL : As I have already mentioned, the time of naming the colours and pictures became shorter through practice. In some cases where the attention was distracted the brain accommodated itself to the changed conditions. It can be stated as a law that the times of cerebral operations become shorter as they become more automatic, hut that a limit is reached beyond which further practice has little or no effect. The investigation was concluded in April ; in July, after an interval of three months during which no reactions were made, the times of the more important processes were again measured. The Table gives the results of five series of simple reactions on light and sound, of five series in which the observer showed by a motion of the hand that he had perceived a white surface, a letter and a colour, and of three series in which he perceived and named .a letter, a word and a colour. The increase or decrease of the time is given in the column headed Df. TABLE XLII. B C R V Df E' V R V Df R' V Lij^lit... Sound.. 13d 122 12 7 -10 - 3 140 121 8 5 1G7 141 13 9 + 17 + 16 167 139 9 6 White.. Lett rr.. Colour.. 212 305 258 12 22 22 + 1 + 19 - 1 211 304 256 6 14 17 254 309 289 13 26 24 + 13 - 3 - 4 254 307 284 8 18 15 Letter . . Word... Colour.. 354 331 402 25 17 33 -41 -58 -92 353 330 400 17 12 23 425 410 609 22 20 71 + 1 + 5 + 8 428 410 600 14 14 50 We now come to the effects of Fatigue. These, like the effects of attention, have been greatly overestimated, experimenters hav- ing made but few reactions in a series or at a sitting, fearing lest the observer should become fatigued and the times unduly long. In order to determine the influence of fatigiio in successive reactions, I took thirty series of simple reactions on light and averaged all the first reactions (as also the mean variation of these reactions) together, all the second reactions, and so on through the twenty-six reactions of which the series was m;ule up. In the sui no way I took two hundred series where the subject had to react (with the hand) after distinguishing an impression, and averaged all the first, second, &c. reactions together. The impres- sions were different in the different series, but of course the same throughout each series. In these series only thirteen determina- tions were made, but twenty-six mental processes took place, it being as fatiguing to see that the object was not there and keep from reacting, as to distinguish the object and react.