524 



PSYCnOLOOT. 



In the latter case, a red and a green signal being added to 

 the former ones, it became, for the same observers, 



0.157 ; 



0.073 ; 



0.132.* 

 Later, in Wundt's Laboratory, Herr Tischer made many- 

 careful experiments after the same method, where the facts 

 to be discriminated were the different degrees of loudness 

 in the sound which served as a signal. I subjoin Herr 

 Tischer's table of results, explaining that each vertical col- 

 umn after the first gives the average results obtained from 

 a distinct individual, and that the figure in the first column 

 stands for the number of possible loudnesses that might be 

 expected in the particular series of reactions made. The 

 times are expressed in thousandths of a second. 



The interesting points here are the. great individual varia- 

 tions, and the rapid way in which the time for discrimina- 

 tion increases with the number of possible terms to dis- 

 criminate. The individual variations are largely due to 

 want of practice in the particular task set, but partly also 

 to discrepancies in the psychic process. One gentleman 

 said, for example, that in the experiments with three 

 sounds, he kept the image of the middle one ready in his 

 mind, and compared what he heard as either louder, lower, 

 or the same. His discrimination among three possibilities 

 became thus very similar to a discrimination between two.;}: 

 Mr. J. M. Cattell found he could get no results by this 

 method,§ and reverted to one used by observers previous 



* Physiol. Psych., ii. 248. 



t Wundt's Philos. Studien, i. 527. 



X Ibid. p. 530. 



§ Mind, XI. 377 ff. He says: " I apparently either distinguished the 

 impression and made the motion simultaneously, or if I tried to avoid this 

 by waiting until I had formed a distinct impression before I began to 

 make the motion, I added to the simple reaction, not only a perception, 

 but a volition." — Which remark may well confirm our doubts as to the 

 strir; psycliologic worth of any of these measurements. 



