workman are satisfied if such a signal is clearly perceivable.
The psychological laboratory experiment, however, shows that the whole
psychophysical effect depends upon the character of the signal; a more
intense light, a quicker change, a higher tone, a larger field of
light, a louder noise, or a harder touch may produce a very different
kind of reaction.

With a careful time-measurement of the motions, it can often be
directly traced how purely technical processes in the machine itself
influence and control the whole psychical system of impulses in the
man. I observed, in a factory, for instance, the work at a machine
which performed most of its functions automatically. It had to hammer
fine grooves into small metal plates. A young laborer stood before
every such machine, took from a pile, alternately from the right and
from the left, the little plates to be serrated, placed them in the
machine, turned a lever to bring the hammer into motion, and then
removed the serrated plates. The speed of the work was dependent upon
the operative, as he determined by his lever movement the instant at
which the automatic serrating hammer should be released. The man's
activity demanded 9 independent movements. I found that those who
worked the most quickly were able to carry out this labor for hours at
a uniform rapidity of 4 to 4-1/2 second for those 9 movements. But the
time-measurement showed that even these fastest workers were
relatively slow in the first 5 movements which they made while the
machine stood quiet, and that they reached an astonishing quickness of
movement in the 4 last actions during which at the same time the
serrating hammer in bewildering rapidity was beating on the plate with
sharp loud cracks. The hammer reinforced the energy of the young
laborers to an effectiveness which could never have been attained by
mere voluntary effort.

Often the simplicity or complication of the stimulus may be decisive
in importance, and this also holds true where the most elementary
reactions are involved, for instance, the mere act of counting which
enters into many industrial functions. Experiments carried on in my
laboratory[31] have shown that the time needed to count a certain
number of units becomes longer as soon as the units themselves become
more complicated. Their inner manifoldness exerts a retarding
influence on the eye as it moves from one figure to another. A certain
psychical inhibition arises; the mind is hel