Bauhaus-Universität Weimar

102 
W■ Smythe Johnson, 
until it was completely fatigued. The make and break contacts of an 
electric key were connected with markers so that each movement of the 
key was recorded on the smoked surface of a revolving drum. - In this 
way each phase of the toe’s movement could be measured; the phases 
were four, namely, the downward movement, the downward rest, the 
upward movement and the upward rest. 
The average tap-time of the subject studied was on the first day 436er ; 
this very regularly decreased until at the close of the practice it was 212®'. 
Likewise, the probable error decreased from 103® to 35®. Moreover, 
the upward rest was longer in the first part of the practice than the other 
three phases combined ; but at the close of the series, it was the same as 
the downward rest, thus showing that the greatest gains in voluntary ac¬ 
tivity are those resulting from the practice of the weakest and less exer¬ 
cised muscles. 
IV. Estimation of time. 
After a number of preliminary tests, the intervals, 82s, 1002, and 
1642 were chosen. The practice lasted from 8 to 16 days on seven 
subjects. 
The results justify the following conclusions: (1) The estimate of a 
given interval varies for different individuals both with and without 
practice. (2) Practice on the same interval may cause the variations 
from the given interval to increase with one person and decrease with 
another. (3) Time estimate is a personal factor depending upon (a) the 
nature of the person, whether of an impulsive or quiet temperament, and 
(b) upon the point of the fixation of the attention, whether to the sen¬ 
sory or the motor side. (4) There is no “ indifference point ” from 
which the subject does not vary with long continued practice. The 
changes that practice produces in the estimation of time are probably 
düe to fixing the attention on the movement to be performed, in which 
case the estimate is shortened in accordance with the growth of auto¬ 
matic control, or to the sensory side in which case the time-estimate is 
made longer by practice. 
V. Regulated rhythmical action. 
In arranging apparatus for this experiment the probable error was 
found for the Edison phonograph to range from 0.2% to 0.7%; for 
the Ludwig kymograph by Baltzar, from 0.2% to 2 % ; for a drum 
run by an Edison motor driven by carefully tended Edison-Lalande 
batteries, for o. 1 % to 3%. The Pfeil marker was found at a break of the 
circuit to have a latent time ranging from 1.1® ± 0.09® with the magnet 
cores distant from the armature to 14.7® ± 0.03® with the cores close to
        

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