EMPLOYMENT PSYCHOLOGY 
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ally dropped off; but eighteen minutes was more than 
enough time for testing one subject. In addition to this, 
the difficulty of the test could be varied not only by in 
creasing the revolutions per minute but by decreasing the 
size of the slot. By means of the slides, these slots could be 
so shortened as to obtain practically the same effect as that 
obtained by increasing the speed of the machine, though 
with far less effort. 
The preliminary study of typical dial machines had 
revealed that the fundamental requirement was the ability 
to acquire a certain bodily rhythm in feeding material 
into the dial and in timing the movements of the hand and 
arm with those of the machine. Some operators acquired 
this rhythm very readily, others only after a long time, 
and still others never. The problem, therefore, was to 
detect these differences so that the most likely candidates 
could be placed at the most difficult machines, the less 
likely at the slower machines, and those who failed entirely 
at work of another kind. When the apparatus described 
was put into use, it soon became evident that it re 
quired a knack similar to that required by dial-machine 
operators, and also that it divided the people who tried 
it into radically different classes. The point which re 
mained to be proved, however, was that those who were 
slow in this test were also slow as dial-machine operators 
and vice versa. In order to determine this, ninety-six 
dial-machine operators in three different shops were tested. 
One of these shops contained slow dial machines, the other 
two contained fast machines. Each operator was given 
three trials of two minutes each, the first two being given 
with the slot wide open, the third with the slot half closed. 
The revolutions per minute were kept constant through 
out. The results were then compared with the piece-work