the black and the red figures, and the counting of the steps, and show
to him in a number of cases how some red figures do not reach the
track, how others go beyond the track, and how some just land in
danger on the track. As soon as he has completely understood the
principle, we turn to the apparatus and he moves the window slowly
over a test card, and tries to find the dangerous spots, and I turn
his attention to every case in which he has omitted one or has given
an incorrect letter. We repeat this slowly until he completely masters
the rules of the game. Only then is he allowed to start the
experiment. I have never found a man with whom this preparation takes
more than a few minutes.

After developing this method in the psychological laboratory, I
turned to the study of men actually in the service of a great electric
railway company which supported my endeavors in the most cordial
spirit. In accordance with my request, the company furnished me with a
number of the best motormen in its service, men who for twenty years
and more had performed their duties practically without accidents,
and, on the other hand, with a large number of motormen who had only
just escaped dismissal and whose record was characterized by many more
or less important collisions or other accidents. Finally, we had men
whose activity as motormen was neither especially good nor especially
bad.

The test of the method lies first in the fact that the tried motormen
agreed that they really pass through the experiment with the feeling
which they have on their car. The necessity of looking out in both
directions, right and left, for possible obstacles, of distinguishing
those which move toward the track from the many which move along the
track, the quick discrimination among the various rates of rapidity,