of the problem, considering that there are electric railway companies
in this country which have up to fifty thousand accident indemnity
cases a year. It therefore seemed to me decidedly worth while to
undertake a laboratory investigation.

It would have been quite possible to treat the functions of the
motormen according to the method which resolves the complex
achievement into its various elements and tests every function
independently. For instance, the stopping of the car as soon as the
danger of an accident threatens is evidently effective only if the
movement controlling the lever is carried out with sufficient
rapidity. We should accordingly be justified in examining the
quickness with which the individual reacts on optical stimuli. If a
playing child suddenly runs across the track of the electric railway,
a difference of a tenth of a second in the reaction-time may decide
his fate. But I may say at once that I did not find characteristic
differences in the rapidity of reaction of those motormen whom the
company had found reliable and those who have frequent accidents. It
seems that the slow individuals do not remain in the service at all.
As a matter of course certain other indispensable single functions,
like sharpness of vision are examined before the entrance into the
service and so they cannot stand as characteristic conditions of good
or bad service among the actual employees.

For this reason, in the case of the motormen I abstracted from the
study of single elementary functions and turned my attention to that
mental process which after some careful observations seemed to me the
really central one for the problem of accidents. I found this to be a
particular complicated act of attention by which the manifoldness of
objects, the pedestrians, the carriages, and the automobiles, are