THE BEST POSSIBLE WORK - CHAPTER III
THE ECONOMY OF MOVEMENT
The study of the technical aspect
of labor can nowhere be separated by a sharp demarcation
line from the study of the labor itself as a function
of the individual organism. Many problems, indeed,
extend in both directions. The student of industrial
efficiency is, for instance, constantly led to the
question of fatigue. He may consider this fatigue
as a function of brain and muscle activity and discuss
it with reference to the psychophysical effort, but
he is equally interested in the question of how far
the apparatus or the machine or the accessory conditions
of the work might be changed in order to avoid fatigue.
The accidents of the electric street railways were
regarded as partly related to fatigue. The problem
was accordingly how to shorten the working time of
the motormen in the interest of the public, but it
was soon recognized that the difficulty might also
be approached from the mere technical side. Some
companies introduced seats which the motormen can
use whenever they feel fatigue coming and excellent
results have followed this innovation. In our
last discussions the technical apparatus stood in
the foreground. We may now consider as our real
topic the psychophysical activity.
Here, too, the leaders of scientific
management have secured some signal successes.
Their chief effort in this field was directed toward
the greatest possible achievement by eliminating all
superfluous movements and by training in those movement
combinations which were recognized as the most serviceable
ones. We may return to the case of the masons
in order to clear up the principle. When Gilbreth
began to reform the labor of the mason after scientific
principles, he gave his chief interest to the men’s
motions. Every muscle contraction which was needed
to move the brick from the pile in the yard to the
final position in the wall was measured with reference
to space-and time-relations and the necessary effort.
From here he turned to the application of well-known
psychophysical principles. A movement is less
fatiguing and therefore economically most profitable
if it occurs in a direction in which the greatest
possible use of gravitation can be made If both hands
have to act at the same time, the labor can be carried
out most quickly and with the smallest effort if corresponding
muscle groups are at work and this means if symmetrical
movements are performed. If unequal movements
have to be made simultaneously, the effort will become
smaller if they are psychically bound together by a
common unified impulse. The distance which has
to be overcome by hands, arms, or feet must be brought
to a minimum for each partial movement. Most
important, however, is this rule. If a definite
combination of movements has been determined as economically
most suitable, this method must be applied without
any exception from the beginning of the learning.
The point is to train from the start those impulse
combinations which can slowly lead to the quickest
and best work. The usual method is the opposite.
Generally the beginner learns to produce from the
beginning work which is as good and correct as possible.
In order to produce such qualitatively good results
at an early stage, it is left to him to choose any
groups of movements which happen to be convenient
to him. Then these become habitual, and as soon
as he tries to go on to quicker work, these chance
habits hinder him in his progress. The movements
which may be best suited for fair production by a
beginner may be entirely unsuited for really quick
work, such as would be expected from an experienced
man. The laborer must replace the first habits
which he has learned by a new set, instead of starting
in the first place with motions which can be continued
until the highest point of efficiency has been reached,
even if this involves rather a poor showing at the
beginning. A final maximum rapidity must be secured
from the start by the choice of those motions which
have been standardized by careful experiments.
It is also psychophysically important
to demand that the movements shall not be suddenly
stopped, if that can be avoided. Any interruption
of a movement presupposes a special effort of the will
which absorbs energy, and after the interruption a
new start must be made of which the same is true.
On the other hand, if chains of movements become habitual,
the psychophysical effort will be reduced to the minimum,
inasmuch as each movement finds its natural end and
is not artificially interrupted by will, and at the
same time each movement itself becomes a stimulus
for the next movement by its accompanying sensations.
The traditional method, for instance, demands that
a brick be lifted with one hand and a trowel with mortar
by the other hand. After that the lifting movement
is interrupted, the brick comes to rest in the hand
of the mason until the mortar has been spread on and
the place prepared for the new brick. Then only
begins a new action with the brick. This method
was fundamentally changed. The laborers learned
to swing the brick with one hand from the pack to
the wall and at the same time to distribute the mortar
over the next brick with the other hand. This
whole complex movement is of course more difficult
and demands a somewhat longer period of learning, but
as soon as it is learned an extreme saving of psychophysical
energy and a correspondingly great economic gain is
secured. The newly trained masons are not even
allowed to gather up with the trowel any mortar which
falls to the floor, because it was found that the loss
of mortar is economically less important than the
waste of psychophysical energy in bending down.
Whoever has once schooled his eye
to observe the limitless waste of human motions and
psychophysical efforts in social life has really no
difficulty in perceiving all this at every step.
This ability to recognize possible savings of impulse
may be brought to a certain virtuosity. Gilbreth,
one of the leaders of the new movement, seems to be
such a virtuoso. When he was in London, there
was pointed out to him in the Japanese British Exhibition
a young girl who worked so quickly that there at least
he would find a rhythm of finger movement which could
not any further be improved. In an exhibition
booth the woman attached advertisement labels to boxes
with phenomenal rapidity. Gilbreth watched her
for a little while and found that she was able to
manage 24 boxes in 40 seconds. Then he told the
young girl that she was doing it wrongly, and that
she ought to try a new way which he showed her.
At the first attempt, she disposed of 24 boxes in 26
seconds and at the second trial in 20 seconds.
She did not have to make more effort for it, but simply
had fewer movements to make. If such economic
gain can be secured with little exertion in the simplest
processes, it cannot be surprising that in the case
of more complex and more advanced technical work which
involves highly skilled labor, a careful psychophysical
study of motions must bring far-reaching economic
improvements.
Yet the more important steps will
have to be guided by special experimental investigations,
and here the psychological laboratory must undertake
the elaboration of the details. Only the systematic
experiment can determine what impulses can be released
at the least expense of energy and with the greatest
exactitude of the motor effect. Investigations
on the psychophysics of movement and the influences
which lead toward making the movement too large or
too small have played an important rôle in the psychological
laboratories for several decades. It was recognized
early that the mistakes which are made in reproducing
a movement may spring from two different sources.
They result partly from an erroneous perception or
memory of the movement carried out, and partly from
the inability to realize the movement intention.
One series of investigations was accordingly devoted
to the studies of those sensations and perceptions
by which we become aware of the actual movement.
Everything which accentuates these sensations must
lead to an overestimation of the motion, and the outcome
is that the movement is made too small. The concentration
of attention, therefore, has the effect of reducing
the actual motion, and the same influence must result
from any resistance which is not recognized as such
and hence is not subtracted in the judgment of the
perceiver. Another series of researches was concerned
with the inner attitude which causes a certain external
movement effect and which may lead to an unintended
amount of movement as soon as the weight to be lifted
is erroneously judged upon. Closely related studies,
finally, deal with a mistake which enters when the
movement is reproduced from memory after a certain
time. The exactitude of a simple arm movement
seems to increase in the first ten seconds, then rapidly
to decrease. The emotional attitude, too, is
of importance for the reproduction of a movement.
I trained myself in making definite extensor and flexor
movements of the arm until I was able to reproduce
them under normal conditions with great exactitude.
In experiments extending over many months, which were
carried on through the changing emotional attitudes
of daily life, the exact measurement showed that both
groups of movements became too large in states of
excitement and too small in states of fatigue.
But in a state of satisfaction and joy the extensor
movement became too large, the flexor movement too
small, and vice versa, in unpleasant emotional
states the flexor movement was too strong and the
extensor movement too weak.
We have a very careful investigation
into the relations between rapidity of movement and
exactitude. The subjects had to perform a hand
movement simultaneously with the beat of a metronome,
the beats of which varied between 20 and 200 in the
minute. In general the accuracy of the movement
decreases as the rapidity increases, but the descent
is not uniform. Motions in the rhythm of 40 to
the minute were on the whole just as exact as those
in the rhythm of 20, and, on the other hand movements
in the rhythm of 200 almost as accurate as those of
140 to the minute. Thus we have a lower limit
below which decrease of rapidity does not increase
the accuracy any further, and an upper limit beyond
which a further increase of rapidity brings no additional
deterioration. The mistakes of the unskilled left
hand increase still more rapidly than the number of
movements. If the eyes are closed, the rapid
movements are usually too long and the slow ones too
short.
An investigation in the Harvard laboratory
varied this problem in a direction which brings it
still nearer to technical conditions of industry.
Our central question was whether the greatest exactitude
of rhythmical movement is secured at the same rapidity
for different muscle groups. We studied especially
rhythmical movements of hand, foot, arm, and head,
and studied them, moreover, under various conditions
of resistance. The result from 340,000 measured
movements was the demonstration that every muscle
group has its own optimum of rapidity for the greatest
possible accuracy and that the complexity of the movement
and the resistance which it finds has most significant
influence on the exactitude of the rhythmical achievement.
If we abstract at first from the fluctuations around
the average value of a particular group of movements
and consider only this average itself in its relation
to the starting movement which it is meant to imitate,
we find characteristic tendencies toward enlargement
or reduction dependent upon the rapidity. The
right foot, for instance, remained nearest to the
original movement at a rapidity of 80 motions in the
minute, while the head did the same at about 20.
For a hand movement of 14 centimeters, the most favorable
rapidity was 120 repetitions in the minute, while
for a hand movement of 1 centimeter the average remained
nearest to the standard at about 40 repetitions.
The mean variation from time average is the smallest
for the left foot at 20 to 30 movements, for the right
at 160 to 180, for the head at 40, for the larger
hand movement at 180, and so on. Investigations
of this kind have so far not affected industrial life
in the least, but it seems hardly doubtful that a
systematic study of the movements necessary for economic
work will have to pass through such strictly experimental
phases. The essential point, however, will be
for the managers of the industrial concerns and the
psychological laboratory workers really to come nearer
to each other from the start and undertake the work
in common, not in the sense that the laboratory is
to emigrate to the factory, but in the better sense
that definite questions which grow out of the industrial
life be submitted to the scientific investigation
of the psychologists.