Wednesday, August 7, 2013


Hugo Münsterberg (June 1, 1863 – December 19, 1916) was a German-American psychologist. He was one of the pioneers in applied psychology, extending his research and theories to Industrial/Organizational (I/O), legal, medical, clinical, educational and business settings. Münsterberg encountered immense turmoil with the outbreak of the First World War. (

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The Riverside Press Cambridge


This book corresponds to a German book, which I published a few months ago, under the title Psychologie und Wirlschaftsleben: Ein Beitrag zur angewandten Experimental-Psychologie (Leipzig: J.A. Barth). It is not a translation, as some parts of the German volume have been abbreviated or entirely omitted and other parts have been enlarged and supplemented. Yet the essential substance of the two books is identical.




































Our aim is to sketch the outlines of a new science which is to intermediate between the modern laboratory psychology and the problems of economics: the psychological experiment is systematically to be placed at the service of commerce and industry. So far we have only scattered beginnings of the new doctrine, only tentative efforts and disconnected attempts which have started, sometimes in economic, and sometimes in psychological, quarters. The time when an exact psychology of business life will be presented as a closed and perfected system lies very far distant. But the earlier the attention of wider circles is directed to its beginnings and to the importance and bearings of its tasks, the quicker and the more sound will be the development of this young science. What is most needed to-day at the beginning of the new movement are clear, concrete illustrations which demonstrate the possibilities of the new method. In the following pages, accordingly, it will be my aim to analyze the results of experiments which have actually been carried out, experiments belonging to many different spheres of economic life. But these detached experiments ought always at least to point to a connected whole; the single experiments will, therefore, always need a general discussion of the principles as a background. In the interest of such a wider perspective we may at first enter into some preparatory questions of theory. They may serve as an introduction which is to lead us to the actual economic life and the present achievements of experimental psychology.
It is well known that the modern psychologists only slowly and very reluctantly approached the apparently natural task of rendering useful service to practical life. As long as the study of the mind was entirely dependent upon philosophical or theological speculation, no help could be expected from such endeavors to assist in the daily walks of life. But half a century has passed since the study of consciousness was switched into the tracks of exact scientific investigation. Five decades ago the psychologists began to devote themselves to the most minute description of the mental experiences and to explain the mental life in a way which was modeled after the pattern of exact natural sciences. Their aim was no longer to speculate about the soul, but to find the psychical elements and the constant laws which control their connections. Psychology became experimental and physiological. For more than thirty years the psychologists have also had their workshops. Laboratories for experimental psychology have grown up in all civilized countries, and the new method has been applied to one group of mental traits after another. And yet we stand before the surprising fact that all the manifold results of the new science have remained book knowledge, detached from any practical interests. Only in the last ten years do we find systematic efforts to apply the experimental results of psychology to the needs of society.
It is clear that the reason for this late beginning is not an unwillingness of the last century to make theoretical knowledge serviceable to the demands of life. Every one knows, on the contrary, that the glorious advance of the natural sciences became at the same time a triumphal march of technique. Whatever was brought to light in the laboratories of the physicists and chemists, of the physiologists and pathologists, was quickly transformed into achievements of physical and chemical industry, of medicine and hygiene, of agriculture and mining and transportation. No realm of the external social life remained untouched. The scientists, on the other hand, felt that the far-reaching practical effect which came from their discoveries exerted a stimulating influence on the theoretical researches themselves. The pure search for truth and knowledge was not lowered when the electrical waves were harnessed for wireless telegraphy, or the Roentgen rays were forced into the service of surgery. The knowledge of nature and the mastery of nature have always belonged together.
The persistent hesitation of the psychologists to make similar practical use of their experimental results has therefore come from different causes. The students of mental life evidently had the feeling that quiet, undisturbed research was needed for the new science of psychology in order that a certain maturity might be reached before a contact with the turmoil of practical life would be advisable. The sciences themselves cannot escape injury if their results are forced into the rush of the day before the fundamental ideas have been cleared up, the methods of investigation really tried, and an ample supply of facts collected. But this very justified reluctance becomes a real danger if it grows into an instinctive fear of coming into contact at all with practical life. To be sure, in any single case there may be a difference of opinion as to when the right time has come and when the inner consolidation of a new science is sufficiently advanced for the technical service, but it ought to be clear that it is not wise to wait until the scientists have settled all the theoretical problems involved. True progress in every scientific field means that the problems become multiplied and that ever new questions keep coming to the surface. If the psychologists were to refrain from practical application until the theoretical results of their laboratories need no supplement, the time for applied psychology would never come. Whoever looks without prejudice on the development of modern psychology ought to acknowledge that the hesitancy which was justified in the beginning would to-day be inexcusable lack of initiative. For the sciences of the mind too, the time has come when theory and practice must support each other. An exceedingly large mass of facts has been gathered, the methods have become refined and differentiated, and however much may still be under discussion, the ground common to all is ample enough to build upon.
Another important reason for the slowness of practical progress was probably this. When the psychologists began to work with the new experimental methods, their most immediate concern was to get rid of mere speculation and to take hold of actual facts. Hence they regarded the natural sciences as their model, and, together with the experimental method which distinguishes scientific work, the characteristic goal of the sciences was accepted too. This scientific goal is always the attainment of general laws; and so it happened that in the first decades after the foundation of psychological laboratories the general laws of the mind absorbed the entire attention and interest of the investigators. The result of such an attitude was, that we learned to understand the working of the typical mind, but that all the individual variations were almost neglected. When the various individuals differed in their mental behavior, these differences appeared almost as disturbances which the psychologists had to eliminate in order to find the general laws which hold for every mind. The studies were accordingly confined to the general averages of mental experience, while the variations from such averages were hardly included in the scientific account. In earlier centuries, to be sure, the interest of the psychological observers had been given almost entirely to the rich manifoldness of human characters and intelligences and talents. In the new period of experimental work, this interest was taken as an indication of the unscientific fancies of the earlier age, in which the curious and the anecdotal attracted the view. The new science which was to seek the laws was to overcome such popular curiosity. In this sign experimental psychology has conquered. The fundamental laws of the ideas and of the attention, of the memory and of the will, of the feeling and of the emotions, have been elaborated. Yet it slowly became evident that such one-sidedness, however necessary it may have been at the beginning, would make any practical application impossible. In practical life we never have to do with what is common to all human beings, even when we are to influence large masses; we have to deal with personalities whose mental life is characterized by particular traits of nationality, or race, or vocation, or sex, or age, or special interests, or other features by which they differ from the average mind which the theoretical psychologist may construct as a type. Still more frequently we have to act with reference to smaller groups or to single individuals whose mental physiognomy demands careful consideration. As long as experimental psychology remained essentially a science of the mental laws, common to all human beings, an adjustment to the practical demands of daily life could hardly come in question. With such general laws we could never have mastered the concrete situations of society, because we should have had to leave out of view the fact that there are gifted and ungifted, intelligent and stupid, sensitive and obtuse, quick and slow, energetic and weak individuals.

But in recent years a complete change can be traced in our science. Experiments which refer to these individual differences themselves have been carried on by means of the psychological laboratory, at first reluctantly and in tentative forms, but within the last ten years the movement has made rapid progress. To-day we have a psychology of individual variations from the point of view of the psychological laboratory.[1] This development of schemes to compare the differences between the individuals by the methods of experimental science was after all the most important advance toward the practical application of psychology. The study of the individual differences itself is not applied psychology, but it is the presupposition without which applied psychology would have remained a phantom.

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Before we discuss some cases of such experimental investigations, we may glance at that other American movement, the well-known systematic effort toward scientific management which has often been interpreted in an expansive literature.[6] Enthusiastic followers have declared it to be the greatest advance in industry since the introduction of the mill system and of machinery. Opponents have hastily denounced it as a mistake, and have insisted that it proved a failure in the factories in which it has been introduced. A sober examination of the facts soon demonstrates that the truth lies in the middle. Those followers of Frederick W. Taylor who have made almost a religion out of his ideas have certainly often exaggerated the practical applicability of the new theories, and their actual reforms in the mills have not seldom shown that the system is still too topheavy; that is, there are too many higher employees necessary in order to keep the works running on principles of scientific management. On the other hand, the opposition which comes from certain quarters,—for instance, from some trade-unions,—may be disregarded, as it is not directed against the claim that the efficiency can be heightened, but only against some social features of the scheme, such as the resulting temporary reduction of the number of workmen. But nobody can deny that this revolutionary movement has introduced most valuable suggestions which the industrial world cannot afford to ignore, and that as soon as exaggerations are avoided and experience has created a broader foundation, the principles of the new theory will prove of lasting value. We shall have to discuss, at a later point, various special features of the system, especially the highly interesting motion study. Here we have to deal only with those tendencies of the movement and with those interests which point toward our present problem, the mental analysis of the individual employees in order to avoid misfits.
The approach to this problem, indeed, seems unavoidable for the students of scientific management, as its goal is an organization of economic work by which the waste of energy will be avoided and the greatest increase in the efficiency of the industrial enterprise will be reached. The recognition that this can never be effected by a mere excessive driving of the workingmen belongs to its very presuppositions. The illusory means of prolongation of the working-time and similar devices by which the situation of the individual deteriorates would be out of the question; on the contrary, the heightening of the individual's joy in the work and of the personal satisfaction in one's total life development belongs among the most important, indirect agencies of the new scheme. This end is reached by many characteristic changes in the division of labor; also by a new division between supervisors and workers, by transformations of the work itself and of the tools and vehicles. But as a by-product of these efforts the demand necessarily arose for means by which the fit individuals could be found for special kinds of labor. The more scientific management introduced changes, by which the individual achievement often had to become rather complicated and difficult, the more it became necessary to study the skill and the endurance and the intelligence of the individual laborers in order to entrust these new difficult tasks only to the most appropriate men in the factories and mills. The problem of individual selection accordingly forced itself on the new efficiency engineers, and they naturally recognized that the really essential traits and dispositions were the mental ones. In the most progressive books of the new movement, this need of emphasizing the selection of workers with reference to their mental equipment comes to clear expression.
Yet this is very far from a real application of scientific psychology to the problem at hand. Wherever the question of the selection of the fit men after psychological principles is mentioned in the literature of this movement, the language becomes vague, and the same men, who use the newest scientific knowledge whenever physics or mathematics or physiology or chemistry are involved, make hardly any attempts to introduce the results of science when psychology is in question. The clearest insight into the general situation may be found in the most recent books by Emerson. He says frankly: "It is psychology, not soil or climate, that enables man to raise five times as many potatoes per acre as the average in his own state";[7] or: "In selecting human assistants such superficialities as education, as physical strength, even antecedent morality, are not as important as the inner attitudes, proclivities, character, which after all determine the man or woman."[8] He also fully recognizes the necessity of securing as early as possible the psychological essentials. He says: "The type for the great newspaper is set up by linotype operators. Apprenticeship is rigorously limited. Some operators can never get beyond the 2500-em class, others with no more personal effort can set 5000 ems. Do the employers test out applicants for apprenticeship so as to be sure to secure boys who will develop into the 5000-em class? They do not: they select applicants for any near reason except the fundamental important one of innate fitness."[9] But all this points only to the existence of the problem, and in reality gives not even a hint for its solution. The theorists of scientific management seem to think that the most subtle methods are indispensable for physical measurements, but for psychological inquiry nothing but a kind of intuition is necessary. Emerson tells how, for instance, "The competent specialist who has supplemented natural gifts and good judgment by analysis and synthesis can perceive attitudes and proclivities even in the very young, much more readily in those semi-matured, and can with almost infallible certainty point out, not only what work can be undertaken with fair hope of success, but also what slight modification or addition and diminution will more than double the personal power."[10] The true psychological specialists surely ought to decline this flattering confidence. Far from the "almost infallible certainty," they can hardly expect even a moderate amount of success in such directions so long as specific methods have not been elaborated, and so long as no way has been shown to make experimental measurements by which such mere guesswork can be replaced by scientific investigation.
The only modest effort to try a step in this direction toward the psychological laboratory is recorded by Taylor,[11] who tells of Mr. S.E. Thompson's work in a bicycle ball factory, where a hundred and twenty girls were inspecting the balls. They had to place a row of small polished steel balls on the back of the left hand and while they were rolled over and over in the crease between two of the fingers placed together, they were minutely examined in a strong light and the defective balls were picked out with the aid of a magnet held in the right hand. The work required the closest attention and concentration. The girls were working ten and a half hours a day. Mr. Thompson soon recognized that the quality most needed, beside endurance and industry, was a quick power of perception accompanied by quick responsive action. He knew that the psychological laboratory has developed methods for a very exact measurement of the time needed to react on an impression with the quickest possible movement; it is called the reaction time, and is usually measured in thousandths of a second. He therefore considered it advisable to measure the reaction-time of the girls, and to eliminate from service all those who showed a relatively long time between the stimulus and reaction. This involved laying off many of the most intelligent, hardest-working, and most trustworthy girls. Yet the effect was the possibility of shortening the hours and of reducing more and more the number of workers, with the final outcome that thirty-five girls did the work formerly done by a hundred and twenty, and that the accuracy of the work at the higher speed was two thirds greater than at the former slow speed. This allowed almost a doubling of the wages of the girls in spite of their shorter working-day, and at the same time a considerable reduction in the cost of the work for the factory. This excursion of an efficiency engineer into the psychological laboratory remained, however; an entirely exceptional case. Moreover, such a reaction-time measurement did not demand any special development of new methods or any particular mental analysis, and this exception thus confirms the rule that the followers of scientific management principles have recognized the need of psychological inquiries, but have not done anything worth mentioning to apply the results of really scientific psychology. Hence the situation is the same as in the field of vocational guidance. In both cases a vague longing for psychological analysis and psychological measurement, but in both cases so far everything has remained on the level of helpless psychological dilettantism. It stands in striking contrast with the scientific seriousness with which the economic questions are taken up in the field of vocational guidance and the physical questions in the field of scientific management. It is, therefore, evidently the duty of the experimental psychologists themselves to examine the ground from the point of view of the psychological laboratory.



We now see clearly the psychotechnical problem. We have to analyze definite economic tasks with reference to the mental qualities which are necessary or desirable for them, and we have to find methods by which these mental qualities can be tested. We must, indeed, insist on it that the interests of commerce and industry can be helped only when both sides, the vocational demands and the personal function, are examined with equal scientific thoroughness. One aspect alone is unsatisfactory. It would of course be possible to confine the examination to the individual mental traits, and then theoretically to determine for which economic tasks the presence of these qualities would be useful and for which tasks their absence or their deficiency would be fatal. Common sense may be sufficient to lead us a few steps in that direction. For instance, if we find by psychological examination that an individual is color-blind for red and green sensations, we may at once conclude, without any real psychological analysis of the vocations, that he would be unfit for the railroad service or the naval service, in which red and green signals are of importance. We may also decide at once that such a boy would be useless for all artistic work in which the nuances of colors are of consequence, or as a laborer in certain departments of a dyeing establishment, and that such a color-blind girl would not do at a dressmaker's or in a millinery store. But if we come to the question whether such a color-blind individual may enter into the business of gardening, in spite of the inability to distinguish the strawberries in the bed or the red flowers among the green leaves, the first necessity, after all, would be to find out how far the particular demands of this vocation make the ability to discriminate color a prerequisite, and how far psychical substitutions such as a recognition of the forms and of differences in the light intensity, may be sufficient for the practical task. Moreover, where not merely such mental defects, but more subtly shaded variations within normal limits are involved, it would be superficial, if only the mental states were examined and not at the same time the mental requirements of the vocations themselves. The vocation should rather remain the starting-point. We must at first find out what demands on the mental system are made by it and we must grade these demands in order to recognize the more or less important ones, and, especially for the important ones, we must then seek exact standards with experimental methods.
Such an experimental investigation may proceed according to either of two different principles. One way is to take the mental process which is demanded by the industrial work as an undivided whole. In this case we have to construct experimental conditions under which this total activity can be performed in a gradual, measurable way. The psychical part of the vocational work thus becomes schematized, and is simply rendered experimentally on a reduced scale. The other way is to resolve the mental process into its components and to test every single elementary function in its isolated form. In this latter case the examination has the advantage of having at its disposal all the familiar methods of experimental psychology, while in the first case for every special vocational situation perfectly new experimental tests must be devised.
Whether the one or the other method is to be preferred must depend upon the nature of the particular commercial or industrial calling, and accordingly presupposes a careful analysis of the special economical processes. It is, indeed, easy to recognize that in certain industrial activities a series of psychical functions is in question whichall lie side by side and which do not fuse into one united total process, however much they may influence one another. But for many industrial tasks just this unity is the essential condition. The testing of the mental elements would be in such cases as insufficient as if we were to test a machine with reference to its parts only and not with reference to its total united performance. Even in this latter case this unified function does not represent the total personality: it is always merely a segment of the whole mental life. We may examine with psychological methods, for instance, the fitness of an employee for a technical vocation and may test the particular complex unified combination of attention, imagination and intelligence, will and memory, which is essential for that special kind of labor. We may be able to reconstruct the conditions so completely that we would feel justified in predicting whether the individual can fulfill that technical task or not; and yet we may disregard entirely the question whether that man is honest or dishonest, whether he is pacific or quarrelsome; in short, whether his mental disposition makes him a desirable member of that industrial concern under other aspects.
We best recognize the significance of these various methods by selecting a few concrete cases as illustrations and analyzing them in detail. But a word of warning may be given beforehand so as to avoid misunderstandings. These examples do not stand here as reports of completed investigations, the results of which ought to be accepted as conclusive parts of the new psychotechnical science; they are not presented as if the results were to be recommended like a well-tested machine for practical purposes. Such really completed investigations do not as yet exist in this field. All that can be offered is modest pioneer work, and just these inquiries into the mental qualities and their relations to the industrial vocations have attracted my attention only very recently, and therefore certainly still demand long continuations of the experiments in every direction. But we may hope for satisfactory results the earlier, the more coöperators are entering the field, and the more such researches are started in other places and in other institutions. I therefore offer these early reports at the first stage of my research merely as stimulations, so as to demonstrate the possibilities.



The problem of securing fit motormen for the electric railways was brought to my attention from without. The accidents which occurred through the fault, or at least not without the fault, of the motormen in street railway transportation have always aroused disquietude and even indignation in the public, and the street railway companies suffered much from the many payments of indemnity imposed by the court as they amounted to thirteen per cent of the gross earnings of some companies. Last winter the American Association for Labor Legislation called a meeting of vocational specialists to discuss the problem of these accidents under various aspects. The street railways of various cities were represented, and economic, physiological, and psychological specialists took part in the general discussion. Much attention was given, of course, to the questions of fatigue and to the statistical results as to the number of accidents and their relation to the various hours of the day and to the time of labor. But there was a strong tendency to recognize as still more important than the mere fatigue, the whole mental constitution of the motormen. The ability to keep attention constant, to resist distraction by chance happenings on the street and especially the always needed ability to foresee the possible movements of the pedestrians and vehicles were acknowledged as extremely different from man to man. The companies claimed that there are motormen who practically never have an accident, because they feel beforehand even what the confused pedestrian and the unskilled chauffeur will do, while others relatively often experience accidents of all kinds because they do not foresee how matters will develop. They can hardly be blamed, as they were not careless, and yet the accidents did result from their personal qualities; they simply lacked the gift of instinctive foresight. All this turned the attention more and more to the possibilities of psychological analysis, and the Association suggested that I undertake an inquiry into this interesting problem with the means of the psychological laboratory. I felt the practical importance of the problem, considering that there are electric railway companies in this country which have up to fifty thousand accident indemnity cases a year. It therefore seemed to me decidedly worth while to undertake a laboratory investigation.
It would have been quite possible to treat the functions of the motormen according to the method which resolves the complex achievement into its various elements and tests every function independently. For instance, the stopping of the car as soon as the danger of an accident threatens is evidently effective only if the movement controlling the lever is carried out with sufficient rapidity. We should accordingly be justified in examining the quickness with which the individual reacts on optical stimuli. If a playing child suddenly runs across the track of the electric railway, a difference of a tenth of a second in the reaction-time may decide his fate. But I may say at once that I did not find characteristic differences in the rapidity of reaction of those motormen whom the company had found reliable and those who have frequent accidents. It seems that the slow individuals do not remain in the service at all. As a matter of course certain other indispensable single functions, like sharpness of vision are examined before the entrance into the service and so they cannot stand as characteristic conditions of good or bad service among the actual employees.
For this reason, in the case of the motormen I abstracted from the study of single elementary functions and turned my attention to that mental process which after some careful observations seemed to me the really central one for the problem of accidents. I found this to be a particular complicated act of attention by which the manifoldness of objects, the pedestrians, the carriages, and the automobiles, are continuously observed with reference to their rapidity and direction in the quickly changing panorama of the street. Moving figures come from the right and from the left toward and across the track, and are embedded in a stream of men and vehicles which moves parallel to the track. In the face of such manifoldness there are men whose impulses are almost inhibited and who instinctively desire to wait for the movement of the nearest objects; they would evidently be unfit for the service, as they would drive the electric car far too slowly. There are others who, even with the car at high speed, can adjust themselves for a time to the complex moving situation, but whose attention soon lapses, and while they are fixating a rather distant carriage, may overlook a pedestrian who carelessly crosses the track immediately in front of their car. In short, we have a great variety of mental types of this characteristic unified activity, which may be understood as a particular combination of attention and imagination.
My effort was to transplant this activity of the motormen into laboratory processes. And here I may include a remark on the methodology of psychological industrial experiments. One might naturally think that the experience of a special industrial undertaking would be best reproduced for the experiment by repeating the external conditions in a kind of miniature form. That would mean that we ought to test the motormen of the electric railway by experiments with small toy models of electric cars placed on the laboratory table. But this would be decidedly inappropriate. A reduced copy of an external apparatus may arouse ideas, feelings, and volitions which have little in common with the processes of actual life. The presupposition would be that the man to be tested for any industrial achievement would have to think himself into the miniature situation, and especially uneducated persons are often very unsuccessful in such efforts. This can be clearly seen from the experiences before naval courts, where it is usual to demonstrate collisions of ships by small ship models on the table in the courtroom. Experience has frequently shown that helmsmen, who have found their course a life long among real vessels in the harbor and on the sea, become entirely confused when they are to demonstrate by the models the relative positions of the ships. Even in the naval war schools where the officers play at war with small model ships, a certain inner readjustment is always necessary for them to bring the miniature ships on the large table into the tactical game. On the water, for instance, the navy officer sees the far-distant ships very much smaller than those near by, while on the naval game table all the ships look equally large. On the whole, I feel inclined to say from my experience so far that experiments with small models of the actual industrial mechanism are hardly appropriate for investigations in the field of economic psychology. The essential point for the psychological experiment is not the external similarity of the apparatus, but exclusively the inner similarity of the mental attitude. The more the external mechanism with which or on which the action is carried out becomes schematized, the more the action itself will appear in its true character.
In the method of my experiments with the motormen, accordingly, I had to satisfy only two demands. The method of examination promised to be valuable if, first, it showed good results with reliable motormen and bad results with unreliable ones; and secondly, if it vividly aroused in all the motormen the feeling that the mental function which they were going through during the experiment had the greatest possible similarity with their experience on the front platform of the electric car. These are the true tests of a desirable experimental method, while it is not necessary that the apparatus be similar to the electric car or that the external activities in the experiment be identical with their performance in the service. After several unsatisfactory efforts, in which I worked with too complicated instruments, I finally settled on the following arrangement of the experiment which seems to me to satisfy those two demands.
The street is represented by a card 9 half-inches broad and 26 half-inches long. Two heavy lines half an inch apart go lengthwise through the centre of the card, and accordingly a space of 4 half-inches remains on either side. The whole card is divided into small half-inch squares which we consider as the unit. Thus there is in any cross-section 1 unit between the two central lines and 4 units on either side. Lengthwise there are 26 units. The 26 squares which lie between the two heavy central lines are marked with the printed letters of the alphabet from A to Z. These two heavy central lines are to represent an electric railway track on a street. On either side the 4 rows of squares are filled in an irregular way with black and red figures of the three first digits. The digit 1 always represents a pedestrian who moves just one step, and that means from one unit into the next; the digit 2 a horse, which moves twice as fast, that is, which moves 2 units; and the digit 3 an automobile which moves three times as fast, that is, 3 units. Moreover, the black digits stand for men, horses, and automobiles which move parallel to the track and cannot cross the track, and are therefore to be disregarded in looking out for dangers. The red digits, on the other hand, are the dangerous ones. They move from either side toward the track. The idea is that the man to be experimented on is to find as quickly as possible those points on the track which are threatened by the red figures, that is, those letters in the 26 track units at which the red figures would land, if they make the steps which their number indicates. A red digit 3 which is 4 steps from the track is to be disregarded, because it would not reach the track. A red digit 3 which is only 1 or 2 steps from the track is also to be disregarded, because it would cross beyond the track, if it took 3 steps. But a red 3 which is 3 units from the track, a red 2 which is 2 units from the track, and a red 1 which is 1 unit from the track would land on the track itself; and the aim is quickly to find these points. The task is difficult, as the many black figures divert the attention, and as the red figures too near or too far are easily confused with those which are just at the dangerous distance.
As soon as this principle for the experiment was recognized as satisfactory, it was necessary to find a technical device by which a movement over this artificial track could be produced in such a way that the rapidity could be controlled by the subject of the experiment and at the same time measured. Again we had to try various forms of apparatus. Finally we found the following form most satisfactory. Twelve such cards, each provided with a handle, lie one above another under a glass plate through which the upper card can be seen. If this highest card is withdrawn; the second is exposed, and from below springs press the remaining cards against the glass plate. The glass plate with the 12 cards below lies in a black wooden box and is completely covered by a belt 8 inches broad, made of heavy black velvet. This velvet belt moves over two cylinders at the front and the rear ends of the apparatus. In the centre of the belt is a window 4-1/2 inches wide and 2-1/2 inches high. If the front cylinder is turned by a metal crank, the velvet belt passes over the glass plate and the little window opening moves over the card with its track and figures. The whole breadth of the card, with its central track and its 4 units on either side, is visible through it over an area of 5 units in the length direction. If the man to be experimented on turns the crank with his right hand, the window slips over the whole length of the card, one part of the card after another becomes visible, and then he simply has to call the letters of those units in the track at which the red figures on either side would land, if they took the number of steps indicated by the digit. At the moment the window has reached Z on the card, the experimenter withdraws that card and the next becomes visible, as a second window in the belt appears at the lower end when the first disappears at the upper end. In this way the subject can turn his crank uninterruptedly until he has gone through the 12 cards. The experimenter notes down the numbers of the cards and the letters which the subject calls. Besides this, the number of seconds required for the whole experiment, from the beginning of the first card to the end of the twelfth, is measured with a stopwatch. This time is, of course, dependent upon the rapidity with which the crank is turned. The result of the experiment is accordingly expressed by three figures, the number of seconds, the number of omissions, that is, of places at which red figures would land on the track which were not noticed by the subject; and, thirdly, the number of incorrect places where letters were called in spite of the fact, that no danger existed. In using the results, we may disregard this third figure and give our attention to the speed and the number of omissions.
The necessary condition for carrying out the experiments with this apparatus is a careful, quiet, practical explanation of the device. The experiment must not under any circumstances be started until the subject completely understands what he has to do and for what he has to look out. For this purpose I at first always show the man one card outside of the apparatus and explain to him the differences between the black and the red figures, and the counting of the steps, and show to him in a number of cases how some red figures do not reach the track, how others go beyond the track, and how some just land in danger on the track. As soon as he has completely understood the principle, we turn to the apparatus and he moves the window slowly over a test card, and tries to find the dangerous spots, and I turn his attention to every case in which he has omitted one or has given an incorrect letter. We repeat this slowly until he completely masters the rules of the game. Only then is he allowed to start the experiment. I have never found a man with whom this preparation takes more than a few minutes.
The test of the method lies first in the fact that the tried motormen agreed that they really pass through the experiment with the feeling which they have on their car. The necessity of looking out in both directions, right and left, for possible obstacles, of distinguishing those which move toward the track from the many which move along the track, the quick discrimination among the various rates of rapidity, the steady forward movement of the observation point, the constant temptation to give attention to those which are still too far away or to those which are so near that they will cross the track before the approach of the car, in short, the whole complex situation with its demands on attention, imagination, and quick adjustment, soon brings them into an attitude which they themselves feel as identical with that in practical life. On the other hand, the results show a far-reaching correspondence between efficiency in the experiment and efficiency in the actual service. With a relatively small number of experiments this correspondence cannot be expected to be complete, the more as a large number of secondary features must enter which interfere with an exact correlation between experiment and standing in the railway company. We must consider, for instance, that those men whom the company naturally selects as models are men who have had twenty to thirty years of service without accidents, but consequently they are rather old men, who no longer have the elasticity of youth and are naturally less able to think themselves into an artificial situation like that of such an experiment, and who have been for a long time removed from contact with book work. It is therefore not surprising, but only to be expected, that such older, model men, while doing fair work in the test, are yet not seldom far surpassed by bright, quick, young motormen who are twenty years younger, even though they are not yet ideal motormen. Moreover, the standing in the company often depends upon features which have nothing to do with the mental make-up of the man, while the experiment has to be confined to these mental conditions which favor accidents. It is quite possible that a man may happen to experience a slight collision, even though no conditions for the accident were lying in his mental make-up. But we may go still further. The experiment refers to those sides of his mind which make him able to foresee the danger points, and that is decidedly the most essential factor and the one from which most can be hoped for the safety of the public. But this does not exclude the possibility that some other mental traits may become causes of accidents. The man may be too daring and may like to run risks, or he may still need discipline, or he may not be sufficiently acquainted with the local conditions. Any such secondary factors may cause some slight accidents with the man who shows rather fair results in the experimental test of his foresight. Finally, we must not forget that some men enter into such tests under a certain nervous tension and therefore may not show so well at the very first test as their mental equipment should allow. Hence it is decidedly desirable not to rely on the first test, but to repeat it. If those various interferences are taken into account, the correspondence between efficiency and the results of the tests is fairly satisfactory. It justified me in proposing that the experiments be continued and in regarding it as quite possible that later tests on the basis of this principle may be introduced at the employment of motormen.
A difficulty is presented by the valuation of the numerical results. The mere number of omissions alone cannot be decisive, as it is clear that no intelligent man would make any omissions if he should give an unlimited amount of time to it; for instance, if he were to spend fifteen minutes on those 12 cards. But this is the same thing as to say that a motorman would not run over any one if he were to drive his car one mile in an hour. The practical problem is to combine the greatest possible speed with the smallest number of oversights and both factors must therefore be considered. The subject who makes relatively many mistakes but uses a very short time must be acknowledged to be as good as the man who makes fewer mistakes but takes a longer time. In the results which I have gathered in experiments with motormen, no one has gone through those 12 cards in a shorter time than 140 seconds, while the longest time was 427 seconds. On the other hand, no one of the motormen made less than 4 omissions, while the worst ones made 28 omissions. I abstract from one extreme case with 36 omissions. On the whole, we may say that the time fluctuates between 180 and 420, the mistakes between 4 and 28. The aim is to find a formula which gives full value to both factors and makes the material directly comparable in the form of one numerical value instead of the two. If we were simply to add the number of seconds and the number of omissions, the omissions would count far too little, inasmuch as 10 additional omissions would then mean no more than 10 additional seconds. On the other hand, if we were to multiply the two figures the omissions would mean by far too much, as the transition from 4 mistakes to 8 mistakes would then be as great a change as the transition from 200 to 400 seconds, that is, from the one extreme of time to the other. Evidently we balance both factors if we multiply the number of omissions by 10 and add them to the number of seconds. The variations between 4 and 28 omissions are 24 steps, which multiplied by 10 correspond to the 240 steps which lie between 180 and 420 seconds. On that basis any additional 50 seconds would be equal to 5 additional omissions. If of two men one takes 100 seconds less than his neighbor, he is equal to him in his ability to satisfy the demands of the service, if he makes 10 mistakes more.
On the basis of this calculation I find that the old, well-trained motormen come to a result of about 450, and I should consider that an average standard. This would mean that a man who uses 400 seconds would not be allowed to make more than 5 omissions, in 350 seconds not more than 10, in 300 not more than 15, in 250 not more than 20, under the condition that these are the results of the first set of experiments. Where there are more than 20 omissions made, mere quickness ought not to be allowed as a substitute. The man who takes 150 seconds and makes 30 mistakes would come up to the same standard level of 450. Yet his characteristics would probably not serve the interests of the service. He would speed up his car and would make better time than any one else, but would be liable to accidents. I should consider 20 mistakes with a time not longer than 250 as the permissible maximum. Among the younger motormen whom I examined, the best result was 290, in which 270 seconds were used and only 2 omissions made. Results below 350 may be considered as very good. One man, for instance, carried out the experiment in 237 seconds with 11 mistakes, which gives the result 347. From 350 to 450 may be counted as fair, 450 to 550 as mediocre, and over 550 as very poor. In the case of old men, who may be expected to adjust themselves less easily to artificial experiments, the limits may be shifted. If the experiments are made repeatedly, the valuation of the results must be changed accordingly. The training of the men in literary and mathematical work or in experimentation may be considered, as our experiments have shown that highly educated young people with long training in experimental observations can pass through the test much more quickly than any one of the motormen could. Among the most advanced graduate students who do research work in my Harvard laboratory there was no one whose result was more than 275, while, as I said, among all the motormen there was no one whose result was less than 290. The best result reached was by a student who passed through the test in 223 seconds with only 1 mistake, the total therefore being 233. Next came a student who did it in 215 seconds with 3 mistakes, total, 245; then in 228 seconds with 2 omissions, total, 248, and so on.

I recapitulate: With men on the educational level and at the age that comes in question for their first appointment in the service of an electric railway company, the test proposed ought to be applied according to this scheme. If they make more than 20 mistakes, they ought to be excluded; if they make less than 20 mistakes, the number of omissions is to be multiplied by 10 and added to the number of seconds. If the sum is less than 350, their mental fitness for the avoidance of accidents is very high, between 350 and 450 fair, and more than 550 not acceptable under any conditions. I submit this, however, with the emphasis on my previous statement that the investigation is still in its first stage, and that it will need a long coöperation between science and industry in order to determine the desirable modifications and special conditions which may become necessary in making the employment of men partly dependent upon such psychological tests. There can be no doubt that the experiments could be improved in many directions. But even in this first, not adequately tested, form, an experimental investigation of this kind which demands from each individual hardly 10 minutes would be sufficient to exclude perhaps one fourth of those who are nowadays accepted into the service as motormen. This 25 per cent of the applicants do not deserve any blame. In many other occupations they might render excellent service; they are neither careless nor reckless, and they do not act against instructions, but their psychical mechanism makes them unfit for that particular combination of attention and imagination which ought to be demanded for the special task of the motorman. If the many thousands of injury and the many hundreds of death cases could be reduced by such a test at least to a half, then the conditions of transportation would have been improved more than by any alterations in the technical apparatus, which usually are the only objects of interest in the discussion of specialists. The whole world of industry will have to learn the great lesson, that of the three great factors, material, machine, and man, the man is not the least, but the most important.