, that no
part of the industrial process is indifferent, even the apparently
most trivial activity, the slightest movement of arm or hand or leg,
became the object of their exact measurement. The stopwatch which
measures every movement in fractions of a second has become the symbol
of this new economic period. As long as special psychological
experiments in the service of industrial psychology are still so
exceptional, it may, indeed, be acknowledged that the practical
experiments in the service of scientific management have come nearest
to the solution of these special psychotechnical problems.

To proceed from without toward the centre, we may begin our review
with the physical technique of the working conditions and its
relations to the mind. Tue history of technique shows on every page
this practical adjustment of external labor conditions to the
psychophysical necessities and psychophysical demands. No machine
with which a human being is to work can survive in the struggle for
technical existence, unless it is to a certain degree adapted to the
human nerve and muscle system and to man's possibilities of
perception, of attention, of memory, of feeling, and of will.
Industrial technique with its restless improvements has always been
subordinated to this postulate. Every change which made it possible
for the workingman to secure equal effects with smaller effort or to
secure greater or better effects with equal effort counted as an
economic gain, which was welcome to the market. For instance,
throughout the history of industry we find the fundamental tendency to
transpose all activities from the great muscles to the small muscles.
Any activity which is performed with the robust muscles of the
shoulder when it can be done with the lower arm, or labor which is
demanded from the muscles of the lower arm when it can just as well be
carried out by the fingers, certainly involves a waste of
psychophysical energy. A stronger psychophysical excitement is
necessary in order to secure the innervation of the big muscles in the
central nervous system. This difference in the stimulation of the
various muscle groups has been of significant consequence for the
differentiation of work throughout the development of mankind.[25]
Labor with the large muscles has, for these psychophysical reasons,
never been easily combined with the subtler training of the finer
muscles. Hence a social organization which obliged the men to give
their e