414 PSYCHOLOGY. 



Wundt's pupil von Tschisch has carried out these ex- 

 periments on a still more elaborate scale,* using, not only 

 the single bell-stroke, but 2, 3, 4, or 5 simultaneous impres- 

 sions, so that the attention had to note the place of the 

 index at the moment when a whole group of things was 

 happening. The single bell-stroke was always heard too 

 early by von Tschisch — the displacement was invariably 

 'negative.' As the other simultaneous impressions were 

 added, the displacement first became zero and finally posi- 

 tive, i.e. the impressions were connected with a position of 

 the index that was too late. This retardation was greater 

 when the simultaneous impressions were disparate (electric 

 tactile stimuli on different places, simple touch-stimuli, 

 different sounds) than when they were all of the same sort. 

 The increment of retardation became relatively less with 

 each additional impression, so that it is probable that six 

 impressions would have given almost the same result as 

 five, which was the maximum number used by Herr von T. 



Wundt explains all these results by his previous obser- 

 vation that a reaction sometimes antedates the signal (see 

 above, p. 411). The mind, he supposes, is so intent upon 

 the bell-strokes that its ' apperception ' keeps ripening 

 periodically after each stroke in anticipation of the next. 

 Its most natural rate of ripening may be faster or slower 

 than the rate at which the strokes come. If faster, then it 

 hears the stroke too early ; if slower, it hears it too late. 

 The position of the index on the scale, meanwhile, is noted 

 at the moment, early or late, at which the bell-stroke is 

 subjectively heard. Substituting several impressions for 



counted 20 seconds, and at the 21st the star seemed removed by ac from 

 the meridian-thread c, whilst at the 22d it was at the distance be ; theu. if 

 ac : be '.: \ : 2, the star would have passed at 21i seconds. The conditions 

 resemble those in our experiment : the star is the index-liand, the threads 

 are the scale ; and a time-displacement is to be expected, which with high 

 rapidities may be positive, and negative with low. The astronomic ob- 

 servations do not permit us to measure its absolute amount ; but that it ex- 

 ists is made certain by the fact than after all other possible errors are elimi- 

 nated, there still remains between different observers a personal difference 

 which is often much larger than that between mere reaction-times, amount- 

 ing . . . sometimes to more than a second." (Op. cit. p. 270.) 

 * Philosophische Studien, ii. 601. 



