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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.

After developing this method in the psychological laboratory, I
turned to the study of men actually in the service of a great electric
railway company which supported my endeavors in the most cordial
spirit. In accordance with my request, the company furnished me with a
number of the best motormen in its service, men who for twenty years
and more had performed their duties practically without accidents,
and, on the other hand, with a large number of motormen who had only
just escaped dismissal and whose record was characterized by many more
or less important collisions or other accidents. Finally, we had men
whose activity as motormen was neither especially good nor especially
bad.

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.


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