which has been written instead of being
concentrated on that which is to be produced by the next writing
movements. The operator himself is not aware of this hindrance. On the
contrary, the public will always be inclined to prefer the typewriters
with visible writing, because by a natural confusion the feeling
arises that the production of the letter is somewhat facilitated, when
the eye is cooeperating, just as in writing with a pen we follow the
lines of the written letter. But the situation lies differently in the
two cases. When we are writing with a pen, the letter grows under our
eyes, while in the machine writing we do not see any part of the
letter until the whole movement which produces the single letter is
finished. By such a misleading analogy many a man is led to prefer the
typewriter with visible writing, while he would probably secure a
greater speed with a machine which does not tempt him to attend the
completed letters, while his entire attention ought to belong to the
following letters.

These last observations point to another psychological aspect of the
machine and of the whole technical work, namely, their relations to
the impressions of the senses. The so-called dynamogenic experiments
of the psychological laboratory have demonstrated what a manifold
influence flows from the sense-impressions to the will-impulses. If
the muscle contraction of a man's fist is measured, the experiment
shows that the strongest possible pressure may be very different when
the visual field appears in different colors, or tones of different
pitch or different noises are stimulating the ear, and so on. As yet
no systematic experiments exist by which such results can be brought
into relation to the sense-stimuli which reach the laborer during his
technical work. The psychophysical effect of colors and noises has not
been fructified at all for industrial purposes. The mere subjective
judgment of the workingman himself cannot be acknowledged as reliable
in such questions. The laborer, for instance, usually believes that a
noise to which he has become accustomed does not disturb him in his
work, while experimental results point strongly to the contrary. In a
similar way the effect of colored windows may appear indifferent to
the workmen, and yet may have considerable influence on his
efficiency. Numberless performances in the factory are reactions on
certain optical or acoustical or tactual signals. Both the engineer
and the