Bauhaus-Universität Weimar

Researches in cross-education. 
explanation of such fatigue is the loss of stored energy in the brain cells. 
In tests of endurance it might be possible to separate the two factors 
which seem to be parallel in the tests involved in our experiments. 
There are, moreover, certain considerations which seem to indicate 
the presence of another factor, one that is probably present under what¬ 
ever conditions the practice is carried on. I have called this factor the 
physiological factor, or cross-influence. 
In the tapping experiments1 it seemed to me highly improbable that a 
strong will was of any aid to the subject. In fact, the men seemed to 
tap more rapidly the less attention they paid to the movement. As sev¬ 
eral expressed the fact, they only needed to “set the machinery going 
and it went itself.” 
Observations were made, too, on F. who practiced with the right foot 
only.2 F. was a strong healthy man, a trained and skilled gymnast. 
During 2^ weeks of practice he was not able to make any marked gain. 
He himself said : “ If I try to hurry too much my foot stops almost alto¬ 
gether. ’ ’ His heavy gymnastic work, in which strong effort is necessary, 
had so developed his ability to send down to large muscles, immense 
stimuli for action, that for a test involving small muscles he could not 
become expert. 
To discover if these observations would be supported by actual experi¬ 
mental results, I arranged the apparatus so that the subjects might tap 
with both hands and both feet, though the tapping of but one member was 
recorded. A sufficient number of records were taken to merit the con¬ 
clusion that, after a few days of practice, enough to take away the awk¬ 
wardness due to thinking of so many members, the right hand could tap 
even more rapidly when tapping together with the other members than 
when tapping alone. It is probable that when the attention was paid 
entirely to one member’s tapping, the motor impulse was too concen- 
tfated for the small muscles ; or else the large impulses, overflowing into 
other muscles, caused contractions that hindered the free movement of 
the muscles concerned in the movement. This surcharging of the small 
muscles was relieved when the attention, and so the impulse, was directed 
to more than one place. 
These observations and results lead us to conclude that the tapping 
^ ls not one of will power as the term is commonly understood. 
ong effort and attention are hindrances to rapid tapping. 
the^eit^er taPP*n& a test in which rapidity is specially dependent on 
e learning of any knack. The test is a very simple one, involving 
Davis, Researches in cross-education, Stud. Yale Psych. Lab., 1898 VI 44. 
Uavis, as before, 12, 13.


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