230 KANSAS UNIVERSITY SCIENCE BULLETIN. 



As the kymograph was run, the horizontal distances between 

 the marks that indicated the sounders and the subject's reac- 

 tion were only about one-fourth of an inch. Consequently 

 little could be determined as to the subject's reaction time. 

 A very long paper would be necessary in order to measure 

 accurately the effect of fatigue upon the time of reaction to 

 sounders. 



It will be noticed that there is nearly always a de- 

 cided increase in ability to discrinimate the sounds in 

 the test following the rest periods for all subjects ex- 

 cept for Do. in the case of the two-hour rests. The 

 sounds were frequently slightly different on one day from 

 what they were the previous day, but the principal factor 

 seemed to be that the subjects seemed to forget the sounds 

 from one day to the next, and the first test served as a means of 

 relearning the relation of the four sounds. The results of Do. 

 would bear out this assumption. As he operated the apparatus 

 for all the other subjects, he was kept more familiar with the 

 sounds the year he was subject with the two-hour rest periods, 

 and consequently did not show improvement in the second test. 

 During the year that Do. acted as subject with the twenty- 

 minute rest periods the sounders were placed in one room with 

 the subject and the rest of the apparatus was in an adjoining 

 room. This prevented the experimenter from hearing more 

 than a very slight click when he operated the sounders, which 

 was in no way similar to the click of the sounders when heard 

 in the same room with them. It will be observed that Do.'s 

 results in this series conform to those of the other subjects. 



Though improvement was manifested after work by three 

 subjects, it was not nearly so great as after the rest interval. 

 It may be that we have here, with the exception of the work of 

 Do., the influence of physical fatigue not only upon the ability 

 to discriminate the sounds, but also upon the memory process. 

 This might mean that the learning process in the first test 

 has been interfered with in some way by the physical work 

 that follows, or that the recall in the second test has been 

 affected by the physical fatigue. Mr. De Camp has conducted 

 a series of experiments (as yet unpublished) * to determine the 

 influence upon learning nonsense syllables of different kinds of 

 work following at various intervals after the learning. The 



* Since the above was written Mr. De Camp's work lias appeared in Psychological 

 Monographs, vol. 19, No. 4. 



