s
can be gained only by an intimate knowledge of the industry. Again I
may give an illustration. In the case of a well-known typesetting
machine, thousand of which are in daily use, I had the impression that
the rapidity of the performance was dependent upon the quickness of
the finger reaction. The managers, on the other hand, have found that
the most essential condition for speed in the whole work is the
ability to retain a large number of words in memory before they are
set. The man who presses the keys rather slowly advances more rapidly
than another who moves his fingers quickly, but must make many pauses
in order to find his place in the manuscript and to provide himself
with new words.

The factors which are to be brought into correlation are, accordingly,
first, the actual experiences of the managers, secondly, the
observations of skilled psychologists in the industrial concerns,
thirdly, psychological and experimental investigations with successful
and unsuccessful laborers, and, fourthly, experimental studies of the
normal variability. If such a programme is to be realized in detail,
it will be necessary to discriminate carefully, between those mental
traits of the personality which must be accredited to a lasting
inherited disposition and such as have been developed under the
influences of the surroundings, by education and training, by bad or
good stimuli from the community. While those acquired traits may have
become relatively lasting dispositions, their transformation is, after
all, possible, and the limits in which changes may be expected will
have to be found out by exact studies. Individual psychological
rhythm, attention and emotion, memory and will energy, disposition to
fatigue and to restoration, imagination, suggestibility and
initiative, and many other features will have to be examined in their
relation to the special economic aims.

Too much emphasis cannot be laid on another function as well, the
experimental testing of which has only recently been started. I refer
to the difference in the individual ability of men to profit from
training. If we test an individual at a certain point in his life with
regard to a variable ability, our result must be dependent upon three
factors, the original disposition for the performance, the original
disposition for the advance by training, and the training itself
actually passed through up to that moment. A small amount of
antecedent training for the parti