Page:Mind (Old Series) Volume 11.djvu/239

238 J. M. CATTELL : If these results are compared with those given in Table I. it will be seen that B's reaction-time for light was lengthened 2, C's 10<r. These increments are very small, falling in the case of B within the limits of the natural variation. The reaction time for sound was the same as when no distracting noise was present. Wundt a found the reaction-time to be considerably lengthened by a distracting noise. This was probably because the subjects had not learned to make the reaction as automatically as B and C. The experiments by Obersteiner 2 are scarcely such as to give accurate results. The attention can be more thoroughly distracted if the brain is busied with some other operation while the reactions are being made. A good w r ay to accomplish this is to let the subject be- ginning with any number add as rapidly as possible 17 after 17 to it. The attention can on the other hand be concentrated to a maximum degree by a voluntary effort of the subject. Many experimenters seem to have attempted this in all their reactions ; Exner, for example, says 3 that although sitting quietly on his seat he would sweat with the exertion. In my experiments the atten- tion was held in a state which I shall describe as normal ; the subject expected the stimulus and reacted at once, but did not strain his attention or make special haste. We have thus three grades of attention : concentrated, normal and distracted. TABLE VI. CONCENTRATED. NORMAL. DISTRACTED. R V R' V R V R' V R V R' V 12. 25. II. 1884. B LIGHT. 189 15 187 8 201 17 197 9 245 28 242 13 C 158 17 156 10 132 16 133 9 153 19 151 10 27. II. 6. III. 1884 B ELECTRIC SHOCK. 160 13 161 7 165 12 164 7 190 16 189 9 C 147 14 147 8 150 15 150 9 184 21 184 11 1 Physiol. Psych., ii., 243. 2 Brain, 1879. 8 Herman's Handb. d. Physiol., II., ii., 287.