DOCKERAY : PHYSICAL FATIGUE AND MENTAL EFFICIENCY. 241 



graph when he was given a standard or incentive than he 

 could do when he was merely told to do his best all the time. 

 In the addition and multiplication tests there was no standard, 

 or at best only a vague one, but in the sounder and in the as- 

 sociation tests the subjects had to keep up to the standard of 

 speed set by the experimenter, and he must keep mentally alert 

 all the time in order to avoid complete confusion of the sound- 

 ers. The result was less possibility of variation, and conse- 

 quently less chance to obscure the effects of physical fatigue. 



Though the addition and the multiplication tests are valu- 

 able tests, the sounder and association tests furnish the more 

 reliable data in this series. The association test was thought 

 to involve more complex processes, and it was expected origi- 

 nally that it would yield more readily to the effects of physical 

 fatigue. However, the results do not differ materially. Fur- 

 ther studies on the effect of physical and mental fatigue upon 

 the attention and association processes are now in progress, 

 and will be reported later. 



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