Bauhaus-Universität Weimar

82 
W. Smythe Johnson, 
4. The duration of maximum rapidity is dependent upon the power 
of the mind for sustained attention. As soon as the attention is diverted 
the movement comes into the control of the automatic centers. The 
speed is consequently decreased, for only by a special effort is speed, either 
muscular or mental, increased above the limit acquired by habit. The 
utmost speed can be maintained only for a few seconds at a time at first, 
but the period may be lengthened by practice. Hence the fluctuations 
in the practice curve are generally due to slight mental fatigue. Al¬ 
though the subject recovers very rapidly at first, yet as the exercise con¬ 
tinues the fluctuations recur more frequently and the periods of recovery 
are lengthened. 
5. Another very important element connected with the duration of one’s 
ability for continuing the exercise, is his knowledge of the time that the 
exercise is to last. If the exercise is to last only a short time, greater 
effort will be put forth in that period than when the exercise is to con¬ 
tinue an hour or more. In long periods of exercise the subject will un¬ 
consciously measure out the energy in proportion to the duration of the 
practice period. For instance, in the experiments made by Oehrn1 in 
memorizing syllables, in making successive additions, and in counting 
letters in groups of threes wherein the exercise was continued from one to 
two hours, the maximum was-reached only in the first instance after 24 
minutes, in the second after 28, and in the third after 59. Contrasted with 
our experiments, his results show that the maximum point depends upon 
the effort put forth in the beginning of the experiment. The results that 
I obtained point to the fact that if Oehrn had shortened the practice 
period, the maximum point would not only have been reached in about 
one tenth of the time, but the progress no doubt would have been greater. 
Nor does the maximum rate of voluntary movement depend upon an 
.innate sense of rhythm as Schaefer2 implies but is, as Camerer3 states, 
one of constant acceleration until the setting in of mental fatigue. In¬ 
stead of a rhythmical fluctuation in the voluntary effort, maintained by 
some investigators, I found no remarkable regularity and am led'to con¬ 
sider it as dependent upon several psycho-physiological processes too 
complicated to have a regular period of oscillation. 
6. Practice does not always mean an absolute gain in efficiency ; it may 
1 Oehrn, Experimentelle Studien zur Individualpsychologie, Psychologische Arbeiten 
(Kraepelin), 1896 I 92. 
2 Schaefer, Canney and Tunstall, On the rhythm of muscular response to voli¬ 
tional impulses in man, Jour. Physiol., 1886 VII 96. 
3 Camerer, Versuche über den zeitlichen Verlauf d. Willensbewegung, 41-45, Tübin¬ 
gen 1866.
        

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