EMPLOYMENT PSYCHOLOGY
118
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 increasing
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 required
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 remained
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 throughout.
The results were then compared with the piece-work
