ny other industrial tasks.

We have emphasized from the start that as a matter of course such a
tested function, while it is taken in its complex unity, is
nevertheless not the only psychophysical disposition of significance.
This is as true for the ship officer as it was for the motorman of the
electric car. If we were to study all the mental dispositions
necessary or desirable for the ship officer, we should find many other
qualities which are accessible to the psychological investigation. The
captain of the ship, for instance, is expected to recognize the
direction of a vessel passing in the fog by the signals of the
foghorn. But so far no one has given any attention to the
psychological conditions of localization of sound, which were for a
long while a much-studied problem of our psychological laboratories.
We know how this localization is dependent upon the comparison of the
two ears and what particular mistakes occur from the different
sensibility of the two ears. Yet there are to-day men on the bridges
of the ships who hear much better with one ear than with the other,
but who still naively believe that, as they hear everything very
distinctly with one ear, this normal ear is also sufficient for
recognizing the direction of the sound. It is the same mistake which
we frequently see among laborers whose vision has become defective in
one of their eyes, or one of whose eyes is temporarily bandaged. They
are convinced that the one good eye is sufficient for their industrial
task, because they are able to recognize everything clearly and
distinctly. They do not know that both the eyes together are necessary
in order to produce that psychological combination by which the visual
impression is projected into the right distance, and that in the
factory they are always in danger of underestimating the distance of a
wheel or some other part of the machine and of letting the hand slip
between the wheels or knives. The results of experimental psychology
will have to be introduced systematically into the study of the
fitness of the personality from the lowest to the highest technical
activity and from the simplest sensory function to the most complex
mental achievement.

X

EXPERIMENTS IN THE INTEREST OF TELEPHONE SERVICE

Our plan was to illustrate the possibility of applying psychological
experiments to the selection of fit applicants also in cases in which
not one characteristic mental function stands out, but