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Where the avoidance of accidents is in question, the test of a special
experimental method can seldom be made dependent upon a comparison
with practical results, as we do not want to wait until the candidate
has brought human life into danger. The ordinary way of reaching the
goal must therefore be an indirect one in such cases. For the study of
motormen the conditions are exceptionally favorable, as hundreds of
thousands of accidents occur every year, but another practical example
may be chosen from a field where it is, indeed, impossible to
correlate the results with actual misfortunes, because the dangerous
situations occur seldom; and nevertheless on account of their
importance they demand most serious study. I refer to the ship
service, where the officer on the bridge may bring thousands into
danger by one single slip of his mind. I turn to this as a further
concrete illustration in order to characterize at once the lengths to
which such vocational studies may advance.

One of the largest ship companies had approached me - long before the
disaster of the Titanic occurred - with the question whether it would
not be possible to find psychological methods for the elimination of
such ship officers as would not be able to face an unexpected suddenly
occurring complication. The director of the company wrote to me that
in his experience the real danger for the great ships lies in the
mental dispositions of the officers. They all know exactly what is to
be done in every situation, but there are too many who do not react in
the appropriate way when an unexpected combination of factors suddenly
confronts them, such as the quick approach of a ship in the fog. He
claimed that two different types ought to be excluded. There are ship
officers who know the requirements excellently, but who are almost
paralyzed when the dangerous conditions suddenly threaten. Their
ability for action is inhibited. In one moment they want to act under
the stimulus of one impression, but before the impulse is realized,
some other perhaps rather indifferent impression forces itself on
their minds and suggests the counteraction, and in this way they
vacillate and remain inactive until it is too late to give the right
order or to press the right button. The other type feels only the
necessity for rapid action, and under the pressure of greatest haste,
without clear thought, they jump to the first decision which rushes
to their minds. Without carefully considering the conditions really
given, they explode in an action which they would never have chosen in
a state of quiet deliberation. They react on any accidental
circumstance, just as at a fire men sometimes carry out and save the
most useless parts of their belongings. Of course, beside these two
types, there is the third type, the desirable one, the men who in the
unexpected situation quickly review the totality of the factors in
their relative importance and with almost instinctive certainty
immediately come to the same decision to which they would have arrived
after quiet thought. The director of the company insisted that it
would be of highest importance for the ship service to discriminate
these three types of human beings, and to make sure that there stand
on the bridge of the ship only men who do not belong to those two
dangerous classes. He turned to me with this request, as he had heard
of the work toward economic psychology in the Harvard laboratory.

As the problem interested me, I carried on a long series of
experiments in order to construct artificial conditions under which
the mental process of decision in a complicated situation, especially
the rapidity, correctness, and constancy of the decision, could be
made measurable. I started from the conviction that this complex act
of decision must stand in definite relation to a number of simpler
mental functions. If, for instance, it stood in a clear definite
relation to the process of association, or discrimination, or
suggestibility, or perception, or memory, and so on, it would be
rather easy to foresee the behavior of the individual in the act of
decision, as every one of those other simple mental functions could be
tested by routine methods of the psychological laboratory. This
consideration led me to propose ramified investigations concerning the
psychology of decision in its relation to the elementary mental
processes. These studies by students of the laboratory are not yet
completed. But I soon saw that they would be unfit for the solution of
my practical problem, as we recognized that these relations between
the complex act of decision and the elementary functions of the
individual seem to have different form with different types of
men.[12] If I was to approach the solution of the practical problem,
accordingly, I had to reproduce in an experimental form the act of
decision under complex conditions.

It seemed necessary to create a situation in which a number of
quantitatively measurable factors were combined without any one of
them forcing itself to consciousness as the most important. The
subject to be experimented on then has to decide as quickly as
possible which of the factors is the relatively strongest one. As
usual, here, too, I began with rather complicated material and only
slowly did I simplify the apparatus until it finally took an entirely
inconspicuous form. But this is surely the most desirable outcome for
testing methods which are to be applied to large numbers of persons.
Complicated instruments, for the handling of which special training is
needed, are never so useful for practical purposes as the simple
schemes which can be easily applied. The form of which I finally made
use is the following. I work with 24 cards of the size of
playing-cards. On the upper half of every one of these cards we have 4
rows of 12 capital letters, namely, A, E, O, and U in irregular
repetition. On 4 cards, one of these vowels appears 21 times and each
of the three others 9 times; on 8 cards, one appears 18 times and
every one of the three others 10 times; on 8 cards, one appears 15
times and each of the others 11 times; and finally, on 4 cards one
vowel appears 16 times, each of the three others 8 times, and besides
them 8 different consonants are mixed in. The person to be tested has
to distribute these 24 cards as quickly as possible in 4 piles, in
such a way that in the first pile are placed all cards in which the
letter A is most frequent, in the second those in which the letter E
predominates, and so on. As a matter of course the result must never
be secured by counting the letters. Any attempt to act against this
prescription and secretly to begin counting would moreover delay the
decision so long that the final result would be an unsatisfactory
achievement anyhow. It would accordingly bring no advantage to the

We measure with a stopwatch in fifths of a second the time for the
whole process from the subject's looking at the first card to his
laying down of the last card, and, secondly, we record the number and
the character of his mistakes, if cards are put into wrong piles. I
have made the experiment with very many persons, and results show that
those various mental traits which have been observed in the practical
ship service come clearly to light under the conditions of this
experiment. Some of the persons lose their heads entirely, and for
many of them it is a painful activity for which they require a long
time. Even if the number of mistakes is not considerable, they
themselves have the feeling that they are not coming to a satisfactory
decision, because their attention is pulled hither and thither so that
they feel an inner mental paralysis. Some chance letters stand out and
appear to them to be predominant, but in the next moment the attention
is captured by some other letters which bring the suggestion that
they are in the majority and that they present the most important
factor. The outcome is that inner state of indecision which can become
so fatal in practical life. Other subjects distribute the cards in
piles at a relatively high speed, and they do it with the subjective
feeling that they have indeed recognized at the first glance the
predominant group of letters. The exact measurement of the results,
however, shows that they commit many errors which would have been
improbable after quiet consideration. Any small group of letters which
catches their eye makes on them, under the pressure of their haste,
such a strong impression that all the other letters are inhibited for
the moment and the wrong decision is quickly made. Finally, we find a
group of persons who carry out the experiment rather quickly and at
the same time with few mistakes. It is characteristic of them to pass
through it with the feeling that it is an agreeable and stimulating
mental activity. In all cases the subjects feel themselves under the
unified impression which results from all those 48 letters of the card
together; and this is the reason why the qualitative manifoldness of a
practical life situation can be compared with these intermingled,
quantitatively determined groups of letters.

If I consider the general results of these experiments only with
reference to the time-measurement, I should say that a person who
completes the distribution of the cards in less than 80 seconds is
quick in his decisions; from 80 to 150, moderately quick; from 150 to
250, slow and deliberate and rather too deliberate for situations
which demand quick action; over 250 seconds, he would belong among
those wavering persons who hesitate too long in a life situation which
demands decision. The time which is needed for the mere distribution
of the cards themselves plays a very small rôle compared with the time
of the whole process, and can be neglected. In order to determine
this, I asked all the subjects before they made the real experiment to
distribute 24 other cards in 4 piles, on each of which one of the four
letters, A, E, O, and U was printed only once. Hence no comparison of
various factors was involved in this form of distribution. The average
time for this ordinary sorting was about 20 seconds. Only rather quick
individuals carried it out in less than 18 and only very slow ones
needed more than 25 seconds. This maximum variation of 10 seconds is
evidently insignificant, as the variations in the experiment amount to
more than 200 seconds. But it is very characteristic that the results
of the two experiments do not move parallel. Some persons, who are
able to sort the cards on which only one of the 4 letters is printed
very quickly, are rather slow when they sort the cards with the 48
letters for which the essential factor is the act of comparison. In
the first case the training in card-playing also seems to have a
certain influence, but in the second case, our real experiment on
decision, this influence does not seem to exist.

We have emphasized from the start that it is no less important to give
consideration to the number of mistakes. A mere rapidity of
distribution with many mistakes characterizes, as we saw, a mental
system which is just as unfit for practical purposes as one which acts
with too great slowness. But it would not have been sufficient simply
to ask how many cards were put into wrong piles. The special
arrangement of the cards with four different types of combinations was
introduced for the purpose of discriminating among mistakes of unequal
seriousness. When one letter appeared 21 times and the three others
only 9 times, it was surely much easier to make the decision than when
the predominant letter appeared only 15 times and the other three each
11 times. The easier the right decision, the graver the mistake. Of
course the valuation of these mistakes must be rather arbitrary. We
decided to value as 4 every mistake in these cards on which the
predominant letter appears 21 times; as 3, a mistake in the 18 letter
cards; as 2, a mistake in the 16 letter cards; and as 1, a mistake in
the most difficult ones, the 15 letter cards. If the mistakes are
calculated on this basis and are added together, a sum below 5 may
indicate a very safe and perfectly reliable ability for decision; 5 to
12, satisfactory; 12 to 20, uncertain; and over 20, very poor. In
order to take account of both factors, time and mistakes, we multiply
the sum of the calculated mistakes by the number of seconds. If the
product of these two figures is less than 400, it may be taken as a
sign of perfect reliability in making very quick, correct decisions,
in complex life situations; 400 to 1000 indicates the limits between
which the ability for such decisions may be considered as normal and
very satisfactory; 1000 to 2000, not good but still adequate; 2000 to
3000, unreliable, and over 3000, practically absent. It is clear that
the real proof of the value of this method cannot be offered. This is
just the reason why we selected this illustration as an example of the
particular difficulty. Wrong decisions, that is, cases in which the
man on the bridge waits too long before he makes his decision and thus
causes a collision of ships by his delay, or in which he rushes
blindly to a decision which he himself would have condemned after
quiet deliberation, are rare. It would be impossible to group such
men together for the purpose of the experiment and to compare their
results with those of model captains, the more as experience has shown
that an officer may have a stainless record for many years and yet may
finally make a wrong decision which shows his faulty disposition. The
test of the method must therefore be a somewhat indirect one. My aim
was to compare the results of the experiments with the experiences of
the various individuals which they themselves reported concerning
their decisions in unexpected complicated situations, and moreover
with the judgments of their friends whom I asked to describe what they
would expect from the subjects under such conditions. The personal
differences in these respects are extremely great, and are also
evident in the midst of small groups of persons who may have great
similarity in their education and training and in many other aspects
of their lives.

Among the most advanced students of my research laboratory, for
instance, all of whom have rather similar schooling and practically
the same training in experimental work, the product of mistakes and
seconds varied between 348 and 13,335. That smallest value occurred in
a case in which the time was 116 seconds and the sum of the mistakes
only 3, inasmuch as 3 cards of the most difficult group where the
predominating letter occurred only 15 times were put in the wrong
piles. The shortest time among my laboratory students was 58 seconds,
but with this individual the sum of the mistakes, calculated on the
basis of the valuation agreed upon, was 13. The largest figure
mentioned resulted in a case in which the student needed 381 seconds
and yet made mistakes the sum of which amounted to 35. It is
characteristic that the person with the smallest product felt a
distinct joy in the experiment, while the one with the largest passed
through painful minutes which put him to real organic discomfort. If
we arrange the men simply in the order of these products, of course we
cannot recognize the various groups, as those who are quick but make
mistakes and those who make few mistakes but act slowly may be
represented by the same products. The coincidence of the results with
the self-characterization is frequently quite surprising. Every one
has at some time come into unexpected, suddenly arising situations and
many have received in such moments a very vivid impression of their
own mental reaction. They know quite well that they could not come to
a decision quickly enough, or that they rushed hastily to a wrong
decision, or that in just such instants a feeling of repose and
security came over them and that with sure instinct they turned in
the direction which they would have chosen after mature thought. The
results of the experiments in sorting the cards confirmed this
self-observation in such frequent cases that it may indeed be hoped
that a more extended test of this method will prove its practical
usefulness. It is clear that the field is a wide one, as these
different types of mental dispositions must be of consequence not only
in the ship service, but also to a certain degree in the railroad
service and in many other industrial tasks.

We have emphasized from the start that as a matter of course such a
tested function, while it is taken in its complex unity, is
nevertheless not the only psychophysical disposition of significance.
This is as true for the ship officer as it was for the motorman of the
electric car. If we were to study all the mental dispositions
necessary or desirable for the ship officer, we should find many other
qualities which are accessible to the psychological investigation. The
captain of the ship, for instance, is expected to recognize the
direction of a vessel passing in the fog by the signals of the
foghorn. But so far no one has given any attention to the
psychological conditions of localization of sound, which were for a
long while a much-studied problem of our psychological laboratories.
We know how this localization is dependent upon the comparison of the
two ears and what particular mistakes occur from the different
sensibility of the two ears. Yet there are to-day men on the bridges
of the ships who hear much better with one ear than with the other,
but who still naïvely believe that, as they hear everything very
distinctly with one ear, this normal ear is also sufficient for
recognizing the direction of the sound. It is the same mistake which
we frequently see among laborers whose vision has become defective in
one of their eyes, or one of whose eyes is temporarily bandaged. They
are convinced that the one good eye is sufficient for their industrial
task, because they are able to recognize everything clearly and
distinctly. They do not know that both the eyes together are necessary
in order to produce that psychological combination by which the visual
impression is projected into the right distance, and that in the
factory they are always in danger of underestimating the distance of a
wheel or some other part of the machine and of letting the hand slip
between the wheels or knives. The results of experimental psychology
will have to be introduced systematically into the study of the
fitness of the personality from the lowest to the highest technical
activity and from the simplest sensory function to the most complex
mental achievement.



Our plan was to illustrate the possibility of applying psychological
experiments to the selection of fit applicants also in cases in which
not one characteristic mental function stands out, but in which a
large number of relatively independent mental activities are in play.
I choose as an illustration of such cases the work of the employees at
the telephone switchboard. A study of the psychological factors in
this work is strongly suggested by the practical interests of the
telephone companies, and may be looked on here exclusively from this
point of view. The user of the telephone is little inclined to
consider how many actions have to be carried out in the central office
before the connection is made and finally broken again. From the
moment when the speaker takes off the receiver to the cutting off of
the connection, fourteen separate psychophysical processes are
necessary in the typical case, and even then it is presupposed that
the telephone girl understood the exchange and number correctly. It is
a common experience of the companies that these demands cannot be
satisfactorily fulfilled when a telephone girl has to handle more than
225 calls in an hour. The official statistics show that this figure is
exceeded in not infrequent cases,[13] in extreme cases the number may
even rise beyond 300. Moreover, in short periods of reinforced demands
it may happen that for a few minutes even the rapidity of 10 calls in
a minute is reached. Normally the burden is divided among the
employees in such a way that about 150 calls fall to each one in an
hour, and that this figure is passed considerably only in one morning
and one evening hour. A skillful distribution of pauses and ample
arrangements for rest, usually together with very excellent hygienic
conditions, make it possible for the fit persons to be able to carry
on this work without over-fatigue from 8 to 9 hours a day. On the
other hand, it is only natural that such rapid and yet subtle activity
under such high tension, where especially the quick localization of
the correct hole is a difficult and yet indispensable part, can be
carried out only by a relatively small number of human nervous
systems. The inability to keep attention at such a high point for a
long while, or to perform such rapid movements, or to retain the
numbers correctly, does not lead to fatal accidents like those in the
case of the unfit motormen, but it does lead to fatigue and finally to
a nervous breakdown of the employees and to confusion in the service.
The result is that the company is continually obliged to dismiss a
considerable proportion of those who have entered the service and who
have spent some months in going through the training school of the
company. As one single company, the Bell Telephone Company, employs
16,000 operators, the problem is an expansive one, and it has bearing
on the health of the employees as well as on the patience of the
subscribers. But above all it refers to the economic interests of the
company, inasmuch as every girl who satisfies the entrance conditions
of hearing and sight, of school education and general personal
appearance, receives some salary throughout the months of training in
the telephone school. Since during the first half-year, in which the
employee still works entirely under supervision, more than a third of
those who had originally entered leave, partly on account of
unfitness, and inability, partly on account of over-fatigue or similar
reasons, the economic disadvantage to the company is evidently a very
great one. The candidates are paid for months of mere training, and
they themselves waste their energy and time with practice in a kind of
labor which cannot be serviceable to them in any other economic
activity. Under these circumstances it is not surprising that one
city system approached me with the question whether it would not
interest me from a scientific point of view to examine how far the
mental fitness of the employees could be determined beforehand through
experimental means.

After carefully observing the service in the central office for a
while, I came to the conviction that it would not be appropriate here
to reproduce the activity at the switchboard in the experiment, but
that it would be more desirable to resolve that whole function into
its elements and to undertake the experimental test of a whole series
of elementary mental dispositions. Every one of these mental acts can
then be examined according to well-known laboratory methods without
giving to the experiments any direct relation to the characteristic
telephone operation as such. I carried on the first series of
experiments with about thirty young women who a short time before had
entered into the telephone training school, where they are admitted
only at the age between seventeen and twenty-three years. I examined
them with reference to eight different psychophysical functions. In
saying this, I abstract from all those measurements and tests which
had somewhat anthropometric character, such as the measurement of the
length of the fingers, the rapidity of breathing, the rapidity of
pulse, the acuity of vision and of hearing, the distinctness of the
pronunciation, and so on. A part of the psychological tests were
carried on in individual examinations, but the greater part with the
whole class together.

These common tests referred to memory, attention, intelligence,
exactitude, and rapidity. I may characterize the experiments in a few
words. The memory examination consisted of reading to the whole class
at first two numbers of 4 digits, then two of 5 digits, then two of 6
digits, and so on up to figures of 12 digits, and demanding that they
be written down as soon as a signal was given. The experiments on
attention, which in this case of the telephone operators seemed to me
especially significant, made use of a method the principle of which

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