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 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 held back by the complexity of the impression and cannot proceed quickly enough to the next. Psychologically no less important is the demand that the external technical conditions so far as they influence consciousness, should remain as far as possible the same, if the same psychical effect is desired, because then only can a perfectly firm connection between stimulus and movement be formed. In technical life this demand is much sinned against. A typical case is that of the signals for which the engineer on the locomotive has to watch. In the daytime the movable arms of the semaphore indicate by their horizontal, oblique, or vertical position whether the tracks are clear. At night-time, on the other hand, the same information reaches him by the different colors of the signal lanterns. From a psychical point of view it is probable that the safety of the service would be increased if an unchangeable connection between signal and movement were formed. It would be sufficient for that purpose if the color signals at night were given up and were replaced by horizontal, oblique, or vertical lines of white light or rows of points. Successful experiments of this kind have been carried on by psychologists in the service of this railroad problem.[32]

The interest in all these problems of large concerns, in transportation and factory work and complex industries, ought not to make us overlook the fact that on principle the same problems can be found in the simplest industrial establishment. Even the housewife or the cook destroys economic values if daily she has to spend useless minutes or hours on account of arrangements in the household which are badly adjusted to the psychological conditions. She sacrifices her energy in vain and she wastes her means where she herself is under the illusion of especial economy. Scientific management would perhaps be nowhere so wholesome as in kitchen and pantry, in laundry and cellar, just because here the saving would be multiplied millionfold and the final sum of energy saved and of feeling values gained would be enormous, even if it could not be calculated with the exactitude with which the savings of a factory budget can be proven. The profusion of small attractive devices which automatically perform the economic household labor and disburden the human workers must not hide the fact that the chief activities are still little adjusted to the psychophysical conditions. The situation is similar to that of the masons, whose function has also been performed for thousands of years, and yet which did not find a real adaptation to the psychical factors until a systematic time-measuring study was introduced. A manufacturer who sells an improved pan or mixing-spoon or broom expects success if he brings to the market something the merits of which are evident and make the housewife anticipate a decrease of work or a simplification of work, but the development of scientific management has shown clearly that the most important improvements are just those which are deduced from scientific researches, without at first giving satisfaction to the laborers themselves, until a new habit has been formed.

Perhaps the most frequent technical activity of this simple kind is sewing by hand, which is still entirely left to the traditions of common sense, and yet which is evidently dependent upon the interplay of many psychical factors which demand a subtle adaptation to the psychical conditions. To approach, at least, this field of human labor a careful investigation of the psychophysics of sewing has been started in my laboratory.[33] The sewing work is done, with the left hand supported, and the right hand connected with a system of levers which make a graphic record of every movement on the smoked surface of a revolving drum. For instance, we begin with simple over and over stitches, measuring the time and the character of the right hand movements for 50 stitches under a variety of technical conditions. The first variation refers to the length of the thread. The thread itself, fixed at the needle's eye, varied between 3 feet and 6 inches in length. Other changes refer to the voluntary speed, to the number of stitches, to fatigue, to external stimuli, to attention, to methods of training, and so on, but the chief interest remains centred on the psychical factors. We are still too much at the beginning already to foresee whether it will be possible to draw from these psychophysical experiments helpful conclusions. The four young women engaged in this laboratory research will later extend it to the psychological conditions of work with the various types of sewing-machines.

XV

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.