in which a
large number of relatively independent mental activities are in play.
I choose as an illustration of such cases the work of the employees at
the telephone switchboard. A study of the psychological factors in
this work is strongly suggested by the practical interests of the
telephone companies, and may be looked on here exclusively from this
point of view. The user of the telephone is little inclined to
consider how many actions have to be carried out in the central office
before the connection is made and finally broken again. From the
moment when the speaker takes off the receiver to the cutting off of
the connection, fourteen separate psychophysical processes are
necessary in the typical case, and even then it is presupposed that
the telephone girl understood the exchange and number correctly. It is
a common experience of the companies that these demands cannot be
satisfactorily fulfilled when a telephone girl has to handle more than
225 calls in an hour. The official statistics show that this figure is
exceeded in not infrequent cases,[13] in extreme cases the number may
even rise beyond 300. Moreover, in short periods of reinforced demands
it may happen that for a few minutes even the rapidity of 10 calls in
a minute is reached. Normally the burden is divided among the
employees in such a way that about 150 calls fall to each one in an
hour, and that this figure is passed considerably only in one morning
and one evening hour. A skillful distribution of pauses and ample
arrangements for rest, usually together with very excellent hygienic
conditions, make it possible for the fit persons to be able to carry
on this work without over-fatigue from 8 to 9 hours a day. On the
other hand, it is only natural that such rapid and yet subtle activity
under such high tension, where especially the quick localization of
the correct hole is a difficult and yet indispensable part, can be
carried out only by a relatively small number of human nervous
systems. The inability to keep attention at such a high point for a
long while, or to perform such rapid movements, or to retain the
numbers correctly, does not lead to fatal accidents like those in the
case of the unfit motormen, but it does lead to fatigue and finally to
a nervous breakdown of the employees and to confusion in the service.
The result is that the company is continually obliged to dismiss a
considerable proportion of those who have entered the service and who