A MEASURE OF MENTAL CAPACITY. 759 



posed four series of problems in addition and multiplication, the 

 written solution of each of which would require at least ten min- 

 utes. He gave them, mostly during the earlier school hours, to 

 pupils of different classes, between eleven and thirteen years of 

 age, so that the pupils would have to make four calculations ten 

 minutes long. Five minutes' pause was given between each prob- 

 lem and the next. The whole experiment thus lasted fifty-five 

 minutes, or about the usual length of a school hour. One hun- 

 dred and sixty-two pupils took part in the exercises, and the re- 

 sults were so nearly uniform that their trustworthiness can not 

 be doubted. The first result was a notable increase of facility in 

 the several sections of the experiment. The number of numbers 

 counted up was about forty per cent larger in the last section 

 than in the first. It was found, however, that not all the pupils 

 shared equally in this advance, but that about forty-three per 

 cent of them showed an evident sinking of efficiency at the end 

 of the hour. The differences in personal susceptibility to fatigue 

 previously observed among adults was also expressed here. This, 

 however, is only a small part of the real results of the experiment. 

 Prof. Burgerstein took pains to determine the number of mistakes 

 committed by the pupils and the corrections they made, in order to 

 estimate the value of the work accomplished in the several sec- 

 tions. Both appeared to increase from the very first, and much 

 more rapidly than the speed of the work. It follows hence in- 

 contestably that the evidences of fatigue in the children under 

 examination make themselves evident with increasing force from 

 the second section of the experiment, and that in the majority of 

 the children it is only outwardly concealed by the likewise in- 

 creasing skill. The quantity of work rose, but its value under- 

 went a constant depreciation. Similar results were obtained by 

 the Russian Sikorski from dictation exercises, and by Hopfner in 

 Berlin from dictations to boys nine years old. 



The general result of these still too limited investigations of 

 the susceptibility of school children to fatigue is the incontestable 

 fact that the demands which the schools make upon the mental 

 capacity of their pupils are far in excess of what they should be. 



Yet this work is never continuous, but is interrupted by numer- 

 ous pauses for rest, which doubtless have considerable influence 

 on the progress of fatigue. The results of Burgerstein and Hopf- 

 ner's experiments would have been much more unsatisfactory if 

 brief pauses had not been interpolated between the different work- 

 ing spells. The remarkable fact was brought out in my experi- 

 ments with adults in addition, in which pauses of ten minutes 

 were interposed between the half -hour tasks, that the efficiency 

 immediately after each pause was much higher than at any time 

 before. This result is explained simply by the different velocities- 



