EXPERIMENTS AND OBSERVATIONS
A. EXPERIMENTAL CONDITIONS
The observations on the horse under ordinary conditions would have been
quite insufficient for arriving at a decision as to the tenability of
the several possible explanations. For this purpose experimentation with
controlled conditions was necessary.
It was necessary, first, that the place in which the experiments were
performed should be guarded against sources of error and interruptions.
Several difficulties stood in the way of the removal of the horse to a
more convenient place. Therefore, a large canvas tent was erected within
the courtyard of Mr. von Osten. This afforded the necessary isolation
without hindering the free movements of the horse. After the essential
part of the experiment had been completed and the problem had been
practically solved, experimentation was sometimes conducted in the open
courtyard. A number of the experiments were also performed in the
horse's stall.
The choice of proper persons to experiment with the horse required
careful consideration. In so far as observations were to be made upon
the questioner, Mr. von Osten was of course indispensable. But to
obviate every objection he, as well as Mr. Schillings, had to be
excluded from the greater part of the experiments, and other persons
had to be selected who could learn to handle the horse. Now one would
have thought that the horse would respond to any moderately efficient
examiner. But as a matter of fact it was found that the horse would not
react at all in the case of the greater number of persons. Again, in the
case of others he would respond once or twice, but would then cease. All
told, Hans responded more or less readily to forty persons, but it was
only when he worked with Mr. von Osten or with Mr. Schillings, that his
responses were at all dependable. For this reason I undertook to
befriend the horse, and by happy chance it came to pass in a short time
he responded as readily to my questions as to those of the two
gentlemen. In a few of these experiments the Count zu Castell, Count R.
von Matuschka and Mr. Schillings undertook the role of questioner. Where
these are not mentioned in the results here published, I myself did the
questioning.
With regard to the number of experiments and their performance, the
following precautions were observed. A sufficiently large number of
tests was made in each series in order to obviate the possibility of the
contention that the horse's errors were due to chance. The conditions of
experimentation were such that the further contention that he happened
to be tired or otherwise indisposed, whenever the reactions seemed to be
inadequate, could not be offered. The possibility of confusing the horse
by means of unwonted conditions also had to be avoided. For this reason
it was necessary to alternate the trial in which procedure was with the
knowledge of the answer on the part of the questioner, with the trial in
which the procedure was without such knowledge. Such precautions had
hitherto been neglected, and therefore those negative results which had
been occasionally obtained in single trials, could not claim objective
validity, even though the persons making the tests were subjectively
convinced.
The course of the experiments was determined by the nature of the
problem itself. By means of a very simple test it was possible to
discover whether or not Hans was able to think independently. He was
confronted with problems in which the procedure was without knowledge of
the answer on the part of the questioner. If under these conditions he
could respond with the correct answer--which could be the result of a
rational process only--then the conclusion that he could think
independently, was warranted. The examination would be closed and Mr.
von Osten would be justified in all he claimed for the horse. If,
however, Hans should fail in this test, then the conclusion that he
could think was by no means warranted, but rather the inference that he
was dependent upon certain stimuli received from the questioner or the
environment. Further investigation would be for the purpose of
discovering the nature of these stimuli.
To ascertain by means of which sense organ or organs the horse might
receive these necessary stimuli, the method of elimination was employed.
We began by excluding visual stimuli by means of a pair of very large
blinders. Should this investigation be without results, then we would
proceed to test the sense of hearing. The elimination of auditory
stimulations would be more difficult, because ear-caps or the closing of
the passage by means of cotton would not give sufficient assurance that
the sound-waves were being interrupted, even if the horse were docile
enough to suffer these appliances. Thereupon would follow the testing of
the sense of smell and of the skin-senses. And finally there might be
involved another still unknown sense, such as seems to exist in the
lower animal-forms. The reader therefore can readily see that the
investigation might possibly have become very complex, and that the
investigator had to be prepared for all of these possibilities.
The results of the experiments and the essential circumstances under
which they were conducted, were in every case recorded immediately.
It goes without saying that in the final formulation of the results, all
values--including those which were not consonant with the majority--were
to be used.
B. EXPERIMENTAL RESULTS
During the course of these experiments Hans wore his accustomed
trappings, i. e., a girdle, light headgear and snaffle, and he either
stood alone, untied, or was held loosely by the bridle either by the
questioner or (though only in a few instances) by his attendant. The
questioner always stood to the right of the horse, as Mr. von Osten had
been accustomed to do. As reward for correct responses Hans received
from the questioner[G]--and from him only--a bit of bread or carrot, and
at times also a square of sugar. Never was a whip applied. From time to
time the horse was led about the courtyard or was allowed to run loose
in order to secure the needful respite. Besides myself there was usually
present Prof. Stumpf and Dr. von Hornbostel, who kept the records, and
frequently also Mr. von Osten. Several times I worked alone with the
horse. The results obtained in the horse's stall were in no respect
different from those got in the course of the experiments carried on in
the courtyard. Whenever a doubt arose as to the number of taps made by
the horse (though this did not frequently occur), then the series in
question was immediately repeated.
[Footnote G: The expressions _questioner_ and _experimenter_ are used
interchangeably in this treatise.]
In this report of the results of our experiments, the reader must bear
in mind that it was impossible to adhere to that order and distribution
of tests which we are wont to require in the case of psychophysical
experiments conducted under regular laboratory conditions. All sorts of
difficulties had to be overcome: unfavorable weather, the crowds of
curious ones, certain peculiarities of the horse--such as shying
whenever the wind rippled the canvas of the tent--and last but not
least, the idiosyncrasies of Mr. von Osten who repeatedly attempted to
interrupt the progress of the experiments.
Since it was evident that different kinds of processes were involved in
solving the problems and since the solutions would be indicated by
tapping, or by movements of the head, or by walking over to the object
to be designated, the results of these three sets of experiments have
been grouped under three corresponding heads.
_I. Problems solved by tapping_
The following tests were made in which the method was such that when the
problem was presented to the horse, the correct solution was known to
none of those present, least of all to the questioner. This method we
shall designate in the following report as "procedure without knowledge"
whereas we shall call the method in which the answer was known to the
questioner, "procedure with knowledge".
In order to discover if the horse could read numbers, a series of cards
on which numerals were blazoned, were exposed to the horse's view in
such a way that none of those present was able to see them, and the
horse was asked to tap the numbers as they were shown. This experiment
was repeated at different times and in all there were 49 tests in which
procedure was without knowledge, and 42 in which procedure was with
knowledge. In the case of the former there were 8% correct responses,
whereas in the case of the latter 98% of the answers were right. As an
example of the course which the series tended to take, we insert the
following, in which Mr. von Osten himself acted as questioner.
Method. No. exposed. No. tapped.
Without knowledge 8 14
With " 8 8
Without " 4 8
With " 4 4
Without " 7 9
With " 7 7
Without " 10 17
With " 10 10
Without " 3 9
With " 3 3 etc.
Whenever the questioner knew the solution, nearly all of the horse's
answers were correct; but when the answers were unknown to the
questioner, the horse's responses were, with only a few exceptions,
quite unsuccessful. Since the few exceptional cases must be regarded as
fortuitous, the conclusion is warranted that the horse was unable to
read numerals without assistance.
In order to discover whether the horse could read words such as "Hans"
or "Stall" or the names of colors, they were written upon placards and
hung up in a row before the horse in such a way that the questioner
could see the individual word but could not immediately recognize the
particular place that each one occupied in the series. The horse was
then asked: "Upon which placard is the word 'Hans'?", "On which is the
word 'Stall'?", etc. In order to make sure, he was required to repeat
each answer.
Then the experimenter would determine for himself the place of the word
in the series and would ask the question again. Fourteen such tests, in
which the procedure was with knowledge on the part of the questioner,
were interspersed with twelve in which the procedure was without such
knowledge. With the latter there were no correct responses, whereas in
the cases of procedure with knowledge 100% of the answers were correct.
Evidently the horse could not read words.
Three words were thereupon whispered in his ear, which he was asked to
spell in accordance with the method described on page 21. Since he had
to indicate first the row, and then the place in the row occupied by the
letter, it took two answers to indicate the position of each letter. I
acted as questioner. The ordering of the table of letters was unknown to
me, except the position of the letter "a", which naturally came first,
and the place of the letter "s", concerning whose position I had
purposely inquired. The words chosen for this experiment were "Arm",
"Rom" (Rome) and "Hans". The horse responded incorrectly in the case of
every letter which was unknown to the questioner. "A" and "s" alone were
given correctly. Thus in spelling the word "Rom" the horse responded
with the series 3, 4; 3, 4; 5, 4; 5, 4; i. e. "jjst", instead of the
correct series: 4, 6; 4, 2; 3, 7. I later selected three other words,
the spelling of which involved the tapping of thirty-two numbers on the
part of Hans, and whose position I had carefully ascertained beforehand.
When these were given to the horse to spell, he responded promptly
without a single error. Evidently Hans was unable to spell without
assistance of some sort from the questioner.
The horse's reputed aptitude in computation was tested in the following
way. Mr. von Osten whispered a number in the horse's ear so that none of
the persons present could hear. Thereupon I did likewise. Hans was asked
to add the two. Since each of the experimenters knew only his own
number, the sum, if known to anyone, could be known to Hans alone. Every
such test was immediately repeated with the result known to the
experimenters. In 31 tests in which the method was procedure without
knowledge, 3 of the horse's answers were correct, whereas in the 31
tests in which the method was procedure with knowledge, 29 of his
responses were correct. Since the three correct answers in the cases in
which procedure was without knowledge evidently were accidental, the
results of this series of experiments show that Hans was unable to solve
arithmetical problems.
For the purpose of discovering whether the horse could at least count,
the Russian kindergarten device, which Mr. von Osten had used in
training, was utilized. The machine was placed before the horse, but the
experimenter turned his back upon it. Before each test, a number of
balls were pushed to one side and Hans's problem was to indicate the
number thus separated. Each test was repeated with procedure with
knowledge. Of eight such experiments Hans responded successfully every
time procedure was with knowledge but failed every time procedure was
without knowledge. Thus 7 balls were at one time designated as 9 and
later as 14, while 6 were at first designated as 12, and later as 10.
Since all these errors could not be accounted for on the ground of
miscounts on the part of the horse, it was evident that Hans is quite
unable to count.
The memory-test was conducted in the following manner. In the absence of
the questioner a number or the name of some day of the week was spoken
to the horse. The experimenter would then return and question him. Of 10
responses 2 were correct, 8 incorrect. Among the correct answers were
the number 3, a number which, as we shall see, Hans was prone to give
under all sorts of conditions, and which therefore meant very little
when given as a correct response. The number 2, on the other hand, was
consecutively indicated by 7, 9, 5, and 3, 8 was given as 5, 6, 4, and
6, consecutively; and finally Wednesday was indicated as the fourteenth
day of the week. After this we undertook the test the horse's far-famed
knowledge of the calendar. Dates, such as Feb. 29, Nov. 12, etc., were
given to Hans and he was asked to indicate on which day of the week they
fell. Sunday was to be indicated by 1, Monday by 2, etc. Of 14 such
tests, 10 were unsuccessful, 4 successful. But in the case of these 4
something very interesting occurred. It happened that during this series
the keeper of the horse was present, and he happened to know the days on
which these dates fell,--as he himself testified. The dates in question
were also little more than a week or so from the day of the experiment,
so they could easily be determined. But as soon as we took more remote
dates both man and beast were hopelessly lost. It was certain that Hans
had no knowledge of the calendar. It is needless to say anything of his
supposed knowledge of cards and coins. Hans plainly was incapable of
the astonishing feats of memory which had been claimed for him.
Finally we investigated Hans' musical ability. In a room adjoining the
horse's stall there was a small harmonica, which spanned the once
accented octave. On this one or more tones were played. The horse was
required to indicate the tone played, the number of tones played and
their relation to one another. For testing his general hearing 20 tests
were given in which the method was procedure without knowledge. Of the
responses only one was correct, and that one was the tone e, for which
the proper response was three taps, but we must bear in mind what has
already been said of the number 3. The tone b was indicated by 11 taps,
although Hans had only learned a scale of one octave and therefore could
respond to only seven tones. In the tests in which the method was
procedure with knowledge, he again, without exception, was successful.
Similar results were obtained in the analysis of compound clangs. In the
cases of procedure without knowledge (although the experimenter here
knew the correct responses, he purposely refrained from thinking of
them) not a single response was correct; while in the cases of procedure
with knowledge, all but one were correct. The following were typical
responses: Three tones were played and the question was asked, "How many
tones were played?" Hans responded first with 4 taps and then with 1.
The tones c, e, g, a, (1, 3, 5, 6) were struck and the question asked,
"Which tone must be eliminated to make the complex a chord?" In the
tests in which the method had been procedure with knowledge, this
question had always been answered correctly, but when procedure was
without knowledge the responses were first 13, a tone which does not
exist for Hans, then 2, a tone which was not given in the clang to be
analyzed, and finally 3, which was not the discordant tone. Hans's
far-famed musical ability was an illusion.
Taking the results of all the tests into consideration, we find that in
the case of procedure with knowledge, 90 to 100% of the responses of the
various series were correct, whereas, in those series of procedure
without knowledge 10%, at most, of the responses were correct. Under the
conditions prevailing during these latter tests, even these 10% must be
regarded as due to chance. To be sure Mr. Grabow, a member of the school
board and an enthusiastic follower of Mr. von Osten (Zeitschrift fuer
Paedagogische Psychologie, Pathologie und Hygiene, Berlin, 1904, Jahrg.
6, Heft. 6, S. 470), mentions a large number of successful tests, which
were supposedly made in accordance with the method of procedure without
knowledge. A thorough analysis of his experiments was not possible,
because the conditions under which they were conducted were not
adequately specified. But I have no doubt that the successful responses
of the horse were due solely to the absence of precautionary measures.
I, too, could cite a number of seemingly correct responses which
demonstrably were due to the absence of adequate precautionary measures.
I therefore repeat: Hans can neither read, count nor make calculations.
He knows nothing of coins or cards, calendars or clocks, nor can he
respond, by tapping or otherwise, to a number spoken to him but a moment
before. Finally, he has not a trace of musical ability.
After all this experimentation it was evident that the horse was unable
to work alone, but was dependent upon certain stimuli from its
environment. The question therefore arose: does the horse get these
stimuli while the question is being put, or during his responses, i. e.,
during the process of tapping.
If Mr. von Osten's opinion was correct, then the process of questioning
played an important part in the success of the experiment. Of course, as
he said, it was not necessary to ask the question aloud; it was
sufficient--curiously enough--that it be inwardly spoken, thanks to the
horse's extraordinary auditory sensitivity. If, however, conditions were
made such that the auditory sense was eliminated, then the animal would
be unable to respond. Such a theory is not quite as absurd as it might
seem at first blush. For Hansen and Lehmann have shown that an acute
auditory organ is able to respond to such delicate stimulation as is
involved in the softest whisper, or even in the so-called nasal whisper
in which the lips are tightly closed.[3] They have attempted thus to
explain any modes of supposed "thought-transference", (cf. page 7).
Since experts on horses agree that the horse has acute auditory
sensitivity, Mr. von Osten seized upon this fact and tried to establish
his theory in the following manner. No response was successfully made on
the part of the horse, he said, when the sound waves caused by his (Mr.
von Osten's) inner speech were deflected from the ear of the horse. This
was the case when he closed nose and mouth while inwardly putting the
question, or deflected the waves from the horse's ear by means of a
placard held before his mouth while speaking, or finally by applying
lined ear-muffs to the horse's ears. If, on the other hand, he closed
only his nose and not his mouth while thus inwardly putting the
question, or if he held the placard so that there was a possibility of
deflecting the sounds to the horse's ear, or if the ear-muffs were of
too sheer a material, then Hans could hear and answer the questions
which for human ears were inaudible. He demonstrated all this by means
of experiments and of 20 tests of the first kind, in which auditory
sensations were supposedly eliminated, 95% of the responses were
incorrect (Hans would always tap too great a number); whereas of 28
tests of the second kind, not a single answer was wrong, just as had
been predicted. Now I have repeated both kinds of tests, but have always
found some correct responses in those cases in which the horse,
supposedly, was unable to hear, a thing which greatly astonished Mr. von
Osten. In fact, the responses of the horse were quite as correct when I
did not even whisper the question inwardly. It was quite clear that
putting the question in any form whatever was wholly unnecessary. Mr.
von Osten's demonstrations to the contrary, which were based upon
erroneous physical principles, are to be explained as cases of vivid
autosuggestions, (but of this, more in Chapter V). After all this
experimentation, it was manifest that the cue was not given to the horse
while the question was being put; it occurred, therefore, at some time
during the process of tapping. But by means of which sense organ was it
received by the horse?
We began by examining the sense of vision, and in the following manner.
Blinders were applied, and it is worthy of mention that Hans made no
attempt to resist. The questioner stood to the right of the horse, so
that the animal knew him to be present and could hear, but not see him.
Hans was requested to tap a certain number. Then the experimenter would
step forward into the horse's field of vision and would put the same
problem again. Since, in the tests of the first kind, Hans would always
make the most strenuous efforts to get a view of the questioner, and
since he would rave and tear at the lines whenever the attempt was made
to tie him,--a thing which he had never done hitherto,--it was
impossible to determine in some cases whether or not he had seen the
questioner during the process of tapping. I am using, therefore, in the
following exposition, besides the two categories of "not seen" and
"seen", a third which I have called "undecided". A total of 102 tests
were made in which large blinders were used. In 35 of these, the
experimenter certainly was "not seen" in 56 cases he was "seen" and the
remaining 11 are "undecided". Under the first of these categories 6% of
Hans's answers were correct (i. e. only two), under the second head 89%
were correct and under the third 18% were right. In other words, the
horse was at a loss the moment he was prevented from seeing the
questioner; whereas his responses were nearly always correct when the
experimenter was in sight, certain proof that the horse's failures are
to be attributed to the elimination of visual stimuli and not to the
general inconvenience occasioned by the blinders. It is evident
therefore, that the horse required certain visual stimuli or signs in
order to make a correct response.[H]
[Footnote H: Throughout this treatise I am using the word "sign," or
"signal," whereas all other writers who have touched upon the
Hans-problem, have always spoken of "aids." Following von Sanden,[4]
however, I would distinguish clearly between the two. I would
designate as aids all immediate stimulations of the horse's body (i.
e. by means of contact), which have been designed with reference to
the animal's physiological movement-mechanism in such a way that
they truly 'aid' him in the production of the required movements. I
would regard as signs on the other hand, all stimulations (whether
mediate or immediate) which are selected without especial regard to
the anatomy or physiology of the horse, and bear no inseparable
relation to the thing to be done but are associated with it at the
will of the trainer. The rider's use of reins, and control by means
of leg-pressure and manner of sitting in the saddle, and the
driver's use of the lines,----all these, then are aids. A simple
pull at the reins, however, is not an aid, but a sign. The whip may
be used for giving signs as well as aids,----the latter, when it
does the work of the spur or of the pressure with the knees, as is
the case with ladies' riding-horses and in lunging. All calls and
all movements of the hand or head merely, on the part of the
trainer, are to be regarded as signs.]
Such unequivocal results, however, were only obtained after we had
provided blinders of sufficient size (15 x 15 centimeters). Mr. von
Osten believing that the horse would not suffer these to be applied, had
at first proposed other measures. He held a slate before his face. Some
of the horse's responses were right, others wrong. The tests were
repeated and were successful as long as I, myself, held the slate before
my face, but not a single one of the responses was correct when another
would attempt to hold the slate before me. Mr. von Osten then brought
forth a kind of bolster which he fastened on the right side of the
horse's face,--the side which was turned toward the questioner. But this
also gave uncertain results. Finally he agreed to apply blinders. But
these were much too small and projected at a great angle from the head
(Mr. von Osten had cut the straps, for he thought they worried the
animal). The result was that only the posterior part of the horse's
normal field of vision was obstructed. Therefore, one could never be
quite sure whether Hans, who--it will be borne in mind--made every
attempt to see the questioner, had not perhaps after all been able to
peer over the edge of the blinder. The number of "undecided" tests,
therefore, became very great. Of 108 tests, only 25 could be placed in
the category of "not seen", 44 in the "seen", and 39, i. e., a third of
the total, in the "undecided." The percentage of correct answers for
these three categories were, respectively: 24%, 82% and 72%. Here we
have once more approximately the same ratio between the categories of
"seen" and "not seen" as in the case of the tests with the smaller
blinders. If we were to count the cases which we had put under the head
of "undecided," in the same category as those in which vision had been
excluded--as Mr. von Osten had done--then one would have been led to the
conclusion that the horse did not need visual signs. Several observers
had thus been led astray: e. g., General Zobel writes in the
"National-Zeitung" (Aug. 28, 1904), that upon request Mr. von Osten had
covered Hans's right eye "by means of some sort of blinder, so that he
was unable to see his instructor", and that Hans did not fail to respond
correctly. We evidently have here to do with the unreliable bolster
mentioned above. Furthermore, Mr. Schillings made a number of tests with
the small blinders, in which 50% of the answers were correct, and
probably in the same manner were obtained the results published in one
of the daily papers (the "Berliner Tageblatt", Dec. 12, 1904), several
days after the publication of the December report, and reading as
follows: "Tests have been made upon Hans with blinders over his eyes and
it is to be noted that, in spite of these, he still responds correctly."
Mention is also made of the experiments noted in Supplement III (page
257), in which Mr. von Osten hid behind the questioner and merely
encouraged the animal by occasional exhortations, but it is not possible
to say with any degree of certainty in how far he was really hidden from
the horse's view.
I would add that the horse--in so far as it was at all possible to
decide--never looked at the persons or the objects which he was to
count, or at the words which he was to read, yet he nevertheless gave
the proper responses. But he would always make the most strenuous
efforts to see the questioner. (See page 43). I would furthermore add
that several experiments, in which Mr. von Osten and the horse were
separated from each other by means of the canvas tent, failed
completely, and that, on the other hand, all tests were successful in
which the questioner was present in the feed-room and the door between
this and the horse's stall was opened wide enough for him to be seen by
the horse. I would also mention that toward evening the responses became
less and less accurate. The conclusion that visual stimuli were here
operative cannot be gainsaid.
It was possible, to be sure, that other senses might also be involved,
but it was certain that auditory sensations did not enter it. This is
shown by the fact that one might remain just as silent while the horse
was tapping his answer as during the putting of the question and yet
obtain a correct response. Hans, furthermore, could scarcely be
distracted by auditory stimulations. If either the experimenter or
anyone else present sought, at a given moment, to interrupt him by such
calls as "Halt", "Wrong", etc., while he was going through the process
of tapping, they very seldom succeeded in their attempt. Even though
such interruption did succeed in seven out of the twenty-one cases in
which it was tried, the assumption is well grounded that the success was
due entirely or almost entirely to minimal movements involuntarily
executed by those attempting the interruption. It is to such minimal
movements that the horse, as we shall see later, promptly reacted. When
the experimenter (Pfungst), himself, made the interjections, which
certainly should have been more effective, we found that the horse was
actually disturbed in only two of the fourteen cases; and finally in ten
consecutive cases of attempted interruption not a single one was
successful. There was almost a complete absence of any ear movements on
the part of the horse, a fact in which I have been borne out by Mr.
Henry Suermondt, the distinguished horseback rider. Indeed, I cannot
recall that Hans ever turned his ears toward me, a fact which is
strikingly curious in the case of a horse so attentive and so spirited
in temper.
Finally, I might also mention that the breathing of the experimenter in
no wise influenced the outcome of the experiment. Whether he held his
breath or breathed on the leg or body of the horse, made no difference.
Investigations of the other senses became needless, for I had, in the
meantime, succeeded in discovering the essential and effective signs in
the course of my observations of Mr. von Osten. These signs are minimal
movements of the head on the part of the experimenter. As soon as the
experimenter had given a problem to the horse, he, involuntarily, bent
his head and trunk slightly forward and the horse would then put the
right foot forward and begin to tap, without, however, returning it each
time to its original position. As soon as the desired number of taps was
given, the questioner would make a slight upward jerk of the head.
Thereupon the horse would immediately swing his foot in a wide circle,
bringing it back to its original position. (This movement, which in the
following exposition we shall designate as "the back step", was never
included in the count.) Now after Hans had ceased tapping, the
questioner would raise his head and trunk to their normal position. This
second, far coarser movement was not the signal for the back-step, but
always followed it. But whenever this second movement was omitted, Hans,
who had already brought back his foot to the original position and had
thereby put it out of commission, as it were, would give one more tap
with his left foot.
If it was true that these movements of the questioner guided the horse
in his tapping, then the following must be shown: First, that the same
movements were observed in Mr. von Osten in every case of successful
response; secondly, that they recurred in the same order or with only
slight individual changes in the case of all who were able to obtain
successful responses from the horse, and that they were absent or
occurred at the wrong time in all cases of unsuccessful response.
Furthermore, it was observed that it was possible to bring about
unsuccessful reactions on the part of the horse as soon as the movements
were voluntarily suppressed, and conversely, that by voluntarily giving
the necessary signs the horse might be made to respond at pleasure; so
that anyone who possessed the knowledge of the proper signs could
thereby gain control over the process of response on the part of the
horse. These requirements have all been fulfilled, as we shall see in
the following pages.
With regard to the regular recurrence of the movements noticed in the
case of Mr. von Osten, I was, after some practice, able to note
carefully their peculiar characteristics. This was rather difficult, not
only on account of their extreme minuteness, but also because that very
vivacious gentleman made sundry accompanying movements and was
constantly moving back and forth. To abstract from these the essential
and really effective movements was truly difficult. It was much easier
to observe these movements in the case of Mr. Schillings, probably on
account of the fewer accompanying movements and perhaps on account of
their greater distinctness. Usually he would raise the entire trunk a
trifle, so that the movements could be noticed from behind. Besides
these, I had an opportunity to observe the Count zu Castell, Mr. Hahn
and the Count Matuschka. All three made the same movements, though
somewhat more minutely than Mr. Schillings, yet none was as slight as
those of Mr. von Osten.[I] I further noticed that Count Matuschka and
Mr. Schillings often showed a tendency to accompany every tap of the
horse with a slight nod of the head, the last being accompanied by a
more pronounced nod and then followed by the upward jerk of the head, in
other words, they beat time with the horse. In the case of the last
three mentioned, for whom the horse responded far less effectively than
for Mr. von Osten or Mr. Schillings, belated or precipitate jerks would
frequently occur. This was found to be true in the case of all other
persons who had failed to elicit adequate responses from the horse.
Often, in both cases, a complete absence of any kind of minimal movement
had been noted. The accuracy of these observations in the case of Mr.
von Osten is attested by Mr. Stumpf and Mr. von Hornbostel, and by these
same gentlemen and Prof. F. Schumann in the case of Mr. Schillings and
myself. They also found these movements to be most minute in the case of
Mr. von Osten. In my case also they pronounced them "minimal, and often
quite imperceptible". All other persons who have seen me work with the
horse, but who were not familiar with the nature of these movements,
never perceived them, no matter how closely they observed me.
[Footnote I: During the tests Mr. von Osten nearly always wore a
slouch hat with a wide rim. The rim, of course, always moved with
the head, and made the movements appear on a larger scale, (in the
ratio of about 3:2, as I was able to ascertain later by graphic
methods). But observation was successful, even at a distance of a
meter and a half, when he worked with head uncovered. And even if
head and forehead were covered entirely, it was still possible to
note the movements by watching the eye-brows. When Mr. Schillings
and the rest of us worked with the horse, we either went bare-headed
or wore only a very small cap.]
Since the doubt was expressed that these movements did not precede but
followed closely upon the back-step of the horse (i. e., that an error
with regard to the time-element was involved), it became important that
time measurements be taken. This was done in the following manner: The
questioner asked the horse to tap numbers from 5 to 20, seldom higher.
He purposely refrained from pronouncing the number, but recorded it
after each test had been completed. This was a matter of indifference to
the horse (see page 42), and had the advantage that the measurement was
not influenced by knowledge on the part of the time-keeper. Two
observers were required, one watching the horse, the other the
questioner. Both observers had fifth-second stop-watches. The larger
face of this watch shows the fifth-second and a hand on the smaller face
indicates the minute. By pressing upon the stem the watch may be set in
motion at any moment desired, and by pressing it once more it may be
instantly stopped, and the time elapsing between the setting in motion
and the stopping may be read on the face. By pressing upon the stem a
third time the hands are brought back to zero, and the watch is ready
for another test. At a moment agreed upon beforehand--usually the third
tap of the horse--both observers started their watches. Practice tests
had shown that this could be done with all the accuracy necessary in
this case. As soon as the observer of the questioner noticed the
latter's head movement he stopped his watch, and as soon as the observer
of the horse noticed the latter's back-step he stopped his watch. Since
the movement of the horse's foot does not occur as a jerk, but is of
greater extent than a jerk would be, it was agreed that the observer was
to stop the watch as soon as he recognized the back-step as such, not
when the foot was being raised from the ground, because it was not then
evident whether the horse would bring it back to the original position
or whether he was preparing to give another tap, nor when he had brought
his foot completely back, but at the moment in which it was evident that
the horse intended to make the back-step. Experimentation had shown that
an agreement as to this moment was possible. A tap with the left foot,
which might possibly follow upon the back-step, could be left out of
account. The difference in time between the two watches would show the
time between the head-jerk of the questioner and the back-step of the
horse,[J] and if the back-step was indeed a reaction upon the
head-jerk, then the watches would have to show a later time for the
back-step than for the head-jerk.
[Footnote J: For the benefit of those who are familiar with
reaction-time experiments of this kind, I would state the following:
The reaction to the head-jerk, on account of the minuteness of the
latter, was sensory throughout, and therefore all precipitate
reactions are entirely wanting. The reaction to the back-step was,
like the preceding one, a reaction to a visual cue. (Hans's tapping
was almost quite inaudible). Both stop-watches were carefully
regulated. In order to eliminate also the constant error which might
possibly arise as a result of some difference in the functioning of
their pressure-mechanism, the two watches were always exchanged in
the different series of tests, by the observer of the man and the
observer of the horse. The two time-measurements obtained by the two
observers contained, of course, the reaction-times of the observers
themselves. In order to equalize the constant error which thereby
arose, it was arranged that each observer should react alternately
now to the man, now to the horse. In order to be perfectly safe, the
reaction-times of those concerned, (von Hornbostel, Pfungst,
Schumann and Stumpf), were later determined in the laboratory by
means of the carefully regulated Hipp chronoscope. Separate
determinations were made of the reactions to the head-jerk and to an
imitation of the horse's back-step. Then the time which one observer
took to react upon a head-jerk, was compared with the reaction-times
of the other observers to the back-step. Since the greatest
difference which was found in this comparison, did not exceed
one-tenth second, the results obtained in the courtyard required no
correction.]
Measurements of this kind were taken for Mr. von Osten, Mr. Schillings
and myself. In the case of the first two it was taken without any
knowledge on their part. They did not even know that they were being
observed, having been told that the measurements were for the sake of
determining the horse's rate. In my case, to be sure, the time could not
be taken without my knowledge. I succeeded, however, in eliminating the
effect of this knowledge on my part. (Cf. pages 88 and 145.) Since the
results obtained in the case of Mr. Schillings quite agree with those
obtained in my case, it is evident they may be considered as being of
equal value.
With regard to the number of tests the following table may be referred
to. The first vertical column gives the name of the questioner, i. e.
the person operating with the horse. The four other columns give the
number of tests made upon each of these. The name of the person who made
the observation in each series is indicated at the head of the column.
It is unnecessary to give the name of the observer of the horse, for the
only difficulty lay in the observation of the questioner. The numerals I
and II indicate two series taken at different times.
-----------------+----------+----------+----------+----------
| v. H. | Pf. | Schu. | St.
-----------------+----------+----------+----------+----------
Questioner. | I II | I II | I II | I II
-----------------+----------+----------+----------+----------
v. Osten | 9 15 | 34 17 | - -- | 8 27
-----------------+----------+----------+----------+----------
Schillings | - -- | 19 17 | 6 16 | - --
-----------------+----------+----------+----------+----------
Pfungst | 6 13 | -- -- | - -- | 9 --
-----------------+----------+----------+----------+----------
We have omitted from this table several tests in which the observer of
the questioner noticed no head jerks whatever, and therefore could not
arrest his stop-watch, although the horse responded correctly. Four
tests of this kind were made by Mr. von Hornbostel, two by Mr. Pfungst,
two by Mr. Schumann and five by Mr. Stumpf. In the case of Mr. Pfungst
the horse gave the unusually high number of fifty taps. The attention of
the observer had been taxed too long and had failed him (two seconds is
the most favorable time). The head-jerk of Mr. von Osten evidently
occurred during a lapse in Mr. Pfungst's attention and therefore
remained unnoticed.
-----------------+----------+----------+----------+----------
| v. H. | Pf. | Schu. | St.
-----------------+----------+----------+----------+----------
Questioner. | I II | I II | I II | I II
-----------------+----------+----------+----------+----------
R. | 44% 60% | 62% 88% | -- -- | 0% 48%
V. Osten. | | | |
W. | 56% 20% | 12% 0% | -- -- |100% 22%
-----------------+----------+----------+----------+----------
R. |100% 92% | -- -- | -- -- |100% --
Pfungst. | | | |
W. | 0% 0% | -- -- | -- -- | 0% --
-----------------+----------+----------+----------+----------
R. | -- -- | 74% 100% | 83% 100% | -- --
Schillings. | | | |
W. | -- -- | 5% 0% | 17% 0% | -- --
-----------------+----------+----------+----------+----------
The results of the experiments are given in the second table. The
general arrangement corresponds to that of the first table. Even though
the absolute number of tests was small, yet for the sake of giving a
better general view, all values are given in percentages. The tests in
which the movement of the questioner had preceded that of the horse--as
had been anticipated--are recorded under "R" (right); under "W" (wrong),
we have recorded those cases in which the testimony of the
stop-watches--contrary to our expectation--indicated that the reverse
order prevailed. Finally, those cases which would complete the 100%, i.
e. those in which the watches indicate simultaneity of the movements in
question, are not recorded.
From this table we may note the following: The time-measurements for Mr.
Schillings and Mr. Pfungst are quite in agreement and go to show that
the order in time of the head movement of the questioner and the
back-step of the horse was exactly what had been expected. The few
contradictory cases which occur in Series I of the observations upon Mr.
Schillings are to be accounted for by the fact that he was here for the
first time the subject of observation, whereas the recorded
time-measurements in the case of Mr. Pfungst had been preceded by a
number of practice tests. The results of the measurements taken in the
case of Mr. von Osten were far less satisfactory. Even if one were to
allow a series containing barely more than 50% of "right" cases as
sufficient proof of the correctness of our expectation regarding the
order of the movements of the questioner and the horse, only three of
the six series obtained with Mr. von Osten as subject, would satisfy
this expectation. However, since four of the six series show a greater
number of cases of simultaneity (their percentage may be easily deduced
by referring to the per cent of "right" and "wrong" cases), the proposed
method would give a distorted view, and therefore it appears that the
more correct method would be to consider simply the numerical ratio of
the "right" and "wrong" cases. Since, furthermore, Series II shows, in
every case, a decided change which is similar for all observers (note
especially Pfungst), there can be no doubt but that practice is here
involved, and that Series II is to be regarded as the true standard.
Throughout this series we find a preponderance of "right" cases.
Therefore, the table unmistakably confirms the expected order in time.
That there were more "wrong" cases with Mr. von Osten as subject than
with the other questioners is to be explained by the fact that the
decisive movements were far less easily observed in this case, than in
that of the other questioners. (See page 49.) We expect that Series III
would show the same results, or approximately the same results in the
case of Mr. von Osten that it did for Mr. Pfungst and Mr. Schillings,
but unfortunately he declined to act as subject. In the meantime,
however, new and decisive proof presented itself which destroyed all
possible doubt.
Before adverting to it, let us consider in a few words the reaction-time
of the horse,--the time elapsing between the final sign of the
questioner and the reaction of the horse (i. e., the back-step).
Unfortunately this time cannot be directly determined. All that can be
ascertained from our time-measurements, is the time intervening between
the moment of the head-jerk and the moment in which the reaction of the
horse is noted. (See page 51). This time averaged, for the 127
measurements, .45 seconds. If we stated the unavoidable error, (obtained
on the basis of extended supplementary measurements which it is not
necessary to consider here) as .15 seconds, and apply it to the value
found above, we obtain .3 seconds as the probable reaction-time of the
horse.[K]
[Footnote K: See page 126 on the corresponding reaction-time in the
case of man. Similar tests have been made in the case of animals in
only one instance, and that for dogs, by E. W. Weyer.[5] But, as
might have been expected, they did not yield any satisfactory
results.]
That the tapping--as well as all other movements of the horse--was
nothing other than a reaction upon certain visual stimuli, was proved
beyond a doubt by the fact that the voluntary execution of the head-jerk
and of other movements--which we will describe in more detail later
on,--brought about all the proper responses on the part of the horse.
Thus, artificial synthesis became the test of the correctness of
analytical observation.
To elucidate; if the questioner retained the erect position he elicited
no response from the horse, say what he would. If, however, he stooped
over slightly, Hans would immediately begin to tap, whether or not he
had been asked a question. It seems almost ridiculous that this should
never have been noticed before, but it is easily understood, for as soon
as the questioner gave the problem he bent forward--be it ever so
slightly--in order to observe the horse's foot the more closely, for the
foot was the horse's organ of speech. Hans would invariably begin to tap
when I stooped to jot down some note I wished to make. Even to lower the
head a little was sufficient to elicit a response, even though the body
itself might remain completely erect. Of thirty tests made in this
position, twenty-nine were successful. Hans would continue to tap until
the questioner again resumed a completely erect posture. If, for
instance, I stooped forward after having told the horse to tap 13, and
if I purposely remained in this position until I had counted 20, he
would, without any hesitation, tap 20. If I asked him to add 3 and 4,
but did not move until 14 was reached, he would tap 14. Twenty-six such
tests gave similar results.
The reaction of the horse upon such a signal for stopping showed slight
modifications according to the time which elapsed between the last tap
and the signal for stopping. These modifications, which had hitherto
been paraded as expressions of the horse's psychical power may be
illustrated by the following schematic figures (Figures 1-4). In all of
them the dotted line _c-d_ represents the ground level; _d_ shows where
the horse's right forefoot was located before he began tapping; _a_ and
_c_, respectively, indicate the place to which the foot is lowered
during the process of tapping. The unbroken line gives the direction of
the back-step.
If Hans, having raised his foot from _a_ to _b_--preparatory to
tapping,--receives the signal at or just before the moment he lowers the
foot, he immediately swings it in a wide circle from _c_ back to its
original position at _d_, (Fig. 1). As a matter of fact _a_ and _c_
coincide, but are juxtaposed in the diagram for the sake of schematic
utility. This was the usual form of the back-step.
[Illustration: FIG. 1.]
If the signal for stopping is given a little after the last tap (Fig.
2), i. e., at the time that the foot is already being raised for another
tap, then the back-step occurs as _a-b-d_. The horse thus gives, at the
moment it receives the signal for stopping, a changed impulse to the
moving foot. The curve, therefore, has a kink at _b_, and the back-step
occurs with seeming hesitancy,--Hans appears not quite certain of his
result.
[Illustration: FIG. 2.]
If the signal be given somewhat later still (Fig. 3), i. e., when the
foot is being lowered to complete a tap, Hans is still able to put on
the brakes--as it were--and draw back his foot before it reaches the
ground. The whole process gives the impression that the horse was just
about to make a "mistake" of one unit, but at the last moment had
bethought himself of the correct answer.
[Illustration: FIG. 3.]
Finally, if the signal be deferred still longer, it becomes impossible
to prevent the extra tap. The back-step again has the same form as in
figure 1; Hans has made a "mistake" in his answer by one unit too many.
Conversely, if the head-jerk of the questioner occurs too soon; i. e.,
at the moment the horse has raised his foot for the final tap to the
height _b_, (Fig. 4), then the tap is not completed,--but the foot,
without touching the ground, makes the curve _b c_{2} d_, back to its
original position. Hans has again made a "mistake" in his answer,--this
time by one unit too few.
[Illustration: FIG. 4.]
All these variations go to show one thing: Hans never knows in advance
which tap is to be the final one. These variations in his reactions
occurred often without having been intended by the questioner. But to
bring them about at will required skill, on account of the shortness of
the time involved in the reaction.
Whenever the signal for stopping--which we have just discussed--was
followed by the complete erection of the head and trunk, Hans would
definitely cease tapping. If, however, the questioner failed to assume a
completely erect position, or if he stooped forward ever so slightly,
the horse would follow the back-step of the right foot with an extra tap
of the left foot. Besides occurring in tests in which Mr. von Osten
assumed the role of questioner, this fact was also noted when the Count
zu Castell and Mr. Schillings acted as subjects. Since the extra tap
just mentioned was not given like the others with the right foot
forward, but with the left foot upon the spot, it was possible for the
horse to execute it with a greater show of energy. This simulated a high
degree of mental certainty on the part of the horse, as if he wished to
indicate that this was the correct solution of the problem and it would
have to stand. In spite of all this, many errors would creep in. It was
possible to prolong this extra tap and thus make it appear more
dilatory. We need hardly add that henceforth it was within the power of
the experimenter to have the tapping executed entirely with the right
foot or with the final extra tap of the left foot. Hitherto the view had
been current that this lay solely within the pleasure of the horse.
If the questioner still inclined forward, still remained in the bent
posture after Hans had given the final tap with his left foot, the horse
would immediately begin to tap once more with his right foot, which had,
in the meantime, become ready for further action. If the head jerk was
then made, Hans would bring his right foot back, give the extra tap with
his left foot, then resume tapping with the right and thus continue
until the questioner once more resumed the erect posture. Thus the horse
on one occasion when I wished him to tap 100, gave--contrary to my
desire--the following response; 39 with the right foot, 1 with the left,
24 with the right, 1 with the left, 35 with the right, and 1 with the
left. Later it became possible for me to cause him to tap 1 right, 1
left, 1 right, 1 left, etc. I could even get him to tap exclusively with
the left foot by standing at his left rather than at his right as had
been customary with his questioners. These taps with the left foot were
executed in a far less elegant fashion than those with the right foot,
and with a great waste of energy. Hans had become a right-handed
individual--as it were--as a result of long habit.
With regard to the distance at which the experimenter directed the
horse, the following may be said: The usual distance was one-quarter to
one-half meter. This holds for all tests hitherto described. Seventy
tests which were made for the purpose of discovering the influence of
change in distance showed that the reaction of the horse upon the
customary signal of the head-jerk was accurate up to a distance of three
and one-half meters. At a distance of three and one-half to four meters
there suddenly occurred a fall of 60-70% in the number of correct
responses. At a distance of four to four and one-half meters only
one-third of the responses were correct, and at a distance beyond four
and one-half meters there were no correct responses. The greater number
of these tests were made in our presence by Mr. von Osten, who was under
the impression that we were testing the accuracy of the horse's hearing,
whereas we were really testing the accuracy of his perception of
movements.
With regard to the different positions which the experimenter might
assume with reference to the horse, the following may be noted: The
normal position was to the right of the horse. If the experimenter stood
immediately in front of Hans, the latter's reaction would be just as
accurate, though he would always turn his head and make desperate
efforts to see the questioner, even though he was held in short by the
reins. When a position immediately behind the horse was taken--a
somewhat dangerous proceeding, since Hans would at once begin to
kick--no response could be obtained until he succeeded in turning far
enough around to get the questioner within view. If he was restrained
from turning completely around, he would at least turn his head,--and
always to the right. One might even turn his back upon Hans during the
tests, for the signal for stopping was not obtained from the face of the
questioner, but from a movement of the head. The following incident will
show to what extent the horse had become accustomed to seeing the
questioner in a certain definite position. For a long time I had been
in the habit--without exception--of standing close to the horse's
shoulder. Mr. von Osten, on the other hand, would stand farther back.
When, on a certain day, I assumed the latter position, the horse would
not suffer it, but would move backward until he had his accustomed view
of me.
Finally we sought to discover by what movements the horse could be made
to cease tapping. We discovered that upward movements served as signals
for stopping. The raising of the head was the most effective, though the
raising of the eyebrows, or the dilation of the nostrils--as in a
sneer--seemed also to be efficacious. However, it was impossible for me
to discover whether or not these latter movements were accompanied by
some slight, involuntary upward movement of the head. The upward
movement of the head was ineffective only when it did not occur as a
jerk, but was executed in a circuitous form,--first upward and then back
again. Such a movement was occasionally observed in the case of Mr. von
Osten. The elevation of the arms or of the elbow nearest the horse, or
the elevation of the entire body was also effective. Even if a placard,
with which the experimenter tried to cover his face, were raised at a
given moment, the horse would make the back-step. On the other hand,
head movements to the right and to the left or forward and back, in
fine, all horizontal movements, remained ineffective. We also found that
all hand movements, including the "wonderfully effective thrust of the
hand into the pocket filled with carrots", brought no response. I might
also change my position and walk forward and then backward some distance
behind the horse, but the back-step would only occur in response to the
characteristic stimulus. After what has been said it is easy to
understand how vain were Mr. Schillings' attempts to disturb the horse
and how naturally he might conclude that Hans was not influenced by
visual signs. Mr. Schillings simply did not know which signs were
effective.
While the horse could thus be interrupted in the process of tapping by
movements which were executed at the level of the questioner's head, yet
movements below this level had the opposite effect. If Hans showed that
he was about to cease tapping before it was desired, it was possible to
cause him to continue by simply bending forward a trifle more. The
greater angle at which the questioner's trunk was now inclined caused
the horse to increase the rate of tapping. The rule may be stated thus:
The greater the angle at which the body inclined forward, the greater
the horse's rate of tapping, and _vice versa_. It was noticeable that
whenever Mr. von Osten asked for a relatively large number--in which
case he always bent farther forward than in the case of smaller
numbers--Hans would immediately begin to tap very swiftly. Not being
entirely satisfied with these observations, the following more exact
measurements were taken. I asked the horse to tap 20. From 1 to 10 I
held my body at a certain constant angle, at 10 I suddenly bent farther
forward and retained this posture until 20 had been reached. If there
existed a relationship between the angle of inclination and the rate of
tapping, then the time for the last ten taps ought to be less than for
the first ten. Of 34 such tests 31 were sucessful. The following are two
specimen series.
The first series consisted of ten tests of 15 taps each. In all cases my
head was bent at an angle of 30 deg. to the axis of the trunk, but I
constantly changed the angle of inclination of the trunk. It was not
possible to measure this angle accurately on account of the rapidity
with which the whole test had to be made. I was able, however, to
differentiate between them with enough accuracy to designate the
smallest angle (about 20 deg.) as belonging to Grade I, and the greatest
angle (about 100 deg.) as belonging to Grade VII. By fixing certain points
in the environment, it was possible to get approximately the same angle
repeatedly. The time from the third to the thirteenth tap was, in all
cases, taken by Prof. Stumpf by means of a stop-watch. The tests were
taken in the following order:
Grade of inclination: I VI II II IV V VI VII
Time for 10 taps: 5.2 4.6 5.0 5.0 4.8 4.8 4.6 4.4 sec.
From this series it will be seen that in the case of the same angle of
inclination (II and VI were repeated and III was omitted) the same rate
obtained in the tapping. In two other tests I constantly increased the
angle of inclination during the 15 taps, and Hans gradually increased
the rate of tapping accordingly.
In a second series I had the horse tap 14, five times. I myself took the
time of the taps up to 7 by means of the stop-watch, while Prof. Stumpf
took the time of the taps from 8 to 13. At 8 I suddenly bent forward a
little more and retained this position until tap 13. The results were as
follows:
Taps 2 to 7 (Pf.): 3.2 2.2-2.4 2.4 2.2-2.4 2.4 seconds.
" 8 to 13 (St.): 2.6 2.0 2.0 2.2 2.2 seconds.
Such good results, however, were possible only after a number of
preliminary practice tests had been made. The experiment was especially
difficult because the horse was often on the point of stopping in the
midst of a test. This was probably due to some unintentional movement
on my part. In such cases I could induce him to continue tapping only by
bending forward still more, but this effected also, as we have seen, an
increase in his rate of tapping. Such tests, of course, could not give
unambiguous results.
The rate of tapping was quite independent of my rate of counting. Thus,
if I counted aloud rapidly, but bent forward only very slightly, the
horse's tapping was slow and lagged behind my count. If I counted slowly
but bent far forward, Hans would tap rapidly and advance beyond my
count. Thus we see that his rate of tapping was in accordance with the
degree of inclination of my body and never in accordance with the rate
of my counting, i. e., it was quite independent of every sort of
auditory stimulation.
Direct observation and a comparison of the records of the time Hans
required in giving to his master responses involving small, medium and
large numbers, with the records of the time which he required to respond
to my questions when I bent only slightly, moderately or very far
forward, proved that the increased rapidity in tapping in the case of
large numbers, which many regarded as an evidence of high intelligence,
(see page 20), was, as a matter of fact, brought about in the way
described. The two series (in each of which the time measured was for 10
taps) are quite in accord. The horse did not tap faster because he had
been given a large number by Mr. von Osten, but because the latter had
bent farther forward.
From all this it readily appears why it was possible to cause Hans to
increase his rate of tapping but not to decrease it. To do the latter
would involve a decrease in the angle of inclination of the body. This
would necessitate the erection of the body. As we have seen, this was
the signal to which Hans reacted by ceasing to tap. And as a matter of
fact we never knew the horse to decrease his rate of tapping in the
course of any single test, except in the case of very large numbers, and
then it was probably due to fatigue. Mr. von Osten insisted that Hans
often slowed down toward the end of a test, "in order to obviate
mistakes", but all the tests in which he tried to demonstrate this to
us, were unsuccessful. In spite of all exhortation, Hans would tap
either uniformly or somewhat more rapidly as soon as his master--in all
probability unconsciously--bent somewhat lower. Only once was such a
test successful. Mr. von Osten--upon our request--asked the horse to
give a certain large number. In this instance the decrease in the rate
of tapping was due to fatigue and had nothing whatever to do with the
desire on the part of the horse to avoid error. Furthermore, Mr. Hahn,
who had visited Hans twenty times and had made careful notes of his
observations, corroborated my statement when he said that he himself
never noted the decrease in rate mentioned. Contrary statements may
perhaps be due to the fact that the tense state of expectancy on the
part of the observer made the interval between the last taps appear
subjectively somewhat longer.
So much for the technique of the tapping. Now a word about the numbers
which Hans tapped. (I refer only to the results obtained in series which
involved no volitional control). The number 1 was very difficult to get.
Hans usually tapped 2 instead. Thus even in the case of Mr. von Osten he
responded five times with 2, and only in the sixth test did he react
correctly. As far as other questioners were concerned, 1 was seldom
ever obtained, except in the case of Mr. Schillings and myself. The
numbers 2, 3 and 4, on the other hand, were very easily obtained and,
above all, 3 seldom failed. 3 seemed to be the horse's favorite number
and was very frequently given instead of other numbers. Thus, one-sixth
of all the horse's incorrect responses which were given to me were in
terms of the number 3. The numbers 5 and 6 were a little more difficult
to obtain and above 10 the difficulty increased rapidly. Indeed, I never
saw Hans respond with a number exceeding 20 to any questioner, Mr.
Schillings and Mr. von Osten excepted. I saw the nine vain attempts of
Count zu Castell to get the number 15, and Count Matuschka's eight
unsuccessful attempts to obtain the number 16 as a response. But even
with Mr. von Osten and Mr. Schillings such failures were not infrequent.
Thus, Mr. von Osten tried five consecutive times to obtain the number
24. I myself did not fare any better at first. But the following table
shows what practice can do. If we compare the percentage of correct
responses (involving the numbers 1 to 7--for which alone I have
sufficient material, viz., 80 to 100 cases), obtained in the first half
of our tests, with that of the second half, we get the following:
For number: 1 2 3 4 5 6 7
In first half of tests: 49, 92, 89, 86, 74, 62, 53%
" second " " " : 92, 95, 92, 98, 97, 86, 96%
From this we see how hard it was at first to get the number 1 and that
failure was as frequent as success, and how much easier it was on the
other hand to get the numbers 2 and 3 (and which, therefore, do not show
any great improvement in the second half of the tests). Beyond the 3 the
percentage of correct responses decreased and the number 7 stood at the
same level as the number 1. In the second half of the tests, all these
differences disappeared and errors were infrequent and seldom exceeded
+1 or -1. These results of practice are not to be accredited to the
horse, but to the experimenter, who was at first quite unskilled. This
difference in results does not appear in the case of Mr. von Osten, for
his initial practice had been had many years previous. The values
obtained in his case were very constant throughout our experimentation
and generally showed something like 90% of correct responses. To be
sure, in his case also, the number 1 was somewhat unfavorable, (79% were
correct responses). But the percentages obtained in his case showed no
improvement whatever throughout our experimentation. We need scarcely
add that with the voluntary control of the giving of the signs, in the
case at least of such small numbers as are here discussed, no errors,
whatever, occurred.
We have discussed the influence of the experimenter, i. e., the one who
asked the horse to tap; now let us consider the influence of others
present upon the horse.
As a general rule, other persons had no effect upon the horse's
responses. This appears from the failure of nearly all tests in which
all of those present--with the exception of the questioner himself--knew
the number which the horse was to tap. Even when the others concentrated
their whole attention upon the number, it profited little as a close
analysis of the 136 cases, which belong under this head in our records,
go to prove. Thus, in the presence of a group of twenty interested
persons--during the absence of Mr. von Osten--twenty-one problems were
given to the horse, the solutions of which were known to everyone but
myself, the questioner. Result: only two correct responses. Only when
there was among the spectators someone to whom the horse was accustomed
to respond or one from whom he regularly received his food, would such
an influence be effective.[L] But such cases were few. The most
important were the following: I at one time whispered a number to Hans
(on the occasion of the tests mentioned on page 37), and Mr. von Osten
asked for it the moment I stepped aside. Hans answered incorrectly even
though I stood close beside Mr. von Osten; I did not, however, think
intently of the number. As soon as I concentrated my attention upon the
number he promptly responded correctly. Further cases are those
mentioned on page 38, in which the keeper of the horse unintentionally
aided in giving four dates which were unknown to all others present,
including the questioner. This single instance shows the necessity of
the rule that during tests in which the method is that of procedure
without knowledge the solutions should be known to no one of those
present. Finally the tests made by the September-Commission and reported
in Supplement III (page 255) may possibly belong under this head. Since
they were not followed out any further, I am unable to render a definite
judgment upon them. In most of these tests the question itself, as put
by Mr. von Osten, was not adequately answered, but curiously enough,
however, the number which had been given to Hans in von Osten's absence
and which formed the initial number of some mathematical operation, was
tapped correctly. This may possibly be explained by the assumption that
this initial number had been retained in the memory of some of those
present, (see page 149, on the "perseverative tendency"), and that the
horse, since he had been working with some of them, responded to one of
those present. Chance may have played some part also.
[Footnote L: Mr. Schillings, however, did succeed in making a number
of tests with the co-operation of others who had never before worked
with the horse. These tests were made under the following
conditions: The horse was standing in his stall, when Mr. Schillings
and another gentleman approached him. There was no one else present.
Mr. Schillings, who tried to remain as passive inwardly, as
possible, asked his partner to think consecutively of different
numbers between one and 20, which thus were known to him alone. Hans
was then commanded by Mr. Schillings to tap the numbers, which he
did, to the great astonishment of the men, and especially of Mr.
Schillings. In like manner Mr. Sander, a staff physician in the
marine, received--so he writes me--three correct responses to four
questions which he put to the horse. It happened also in the case of
two scientific men and finally, too, in my own case when I first
came in contact with the horse, (see page 88). The horse's reaction
was brought about in the same way in every one of these instances.
Mr. Schillings, in bending forward slightly, thereby started the
horse a-tapping, and his companion--just as innocently--interrupted
the process by means of a movement of his head, when the right
number of taps was reached.
I later tried similar experiments together with Mr. Hahn. I was
aware of the answer to the riddle at the time, but he was not. Mr.
Hahn stepped in front of the horse and thought intently of certain
numbers. I did the questioning, that is, I got the horse to tap. In
twelve tests Hans responded correctly in only two instances. In the
ten others he always tapped beyond the number Mr. Hahn had in mind,
e.g., 21 instead of 2, and was evidently awaiting a movement on my
part. When we exchanged roles, Mr. Hahn doing the questioning and I
doing the "thinking," the horse would not respond at all, although
as a rule Mr. Hahn had been fairly successful in working with him
alone. I had gradually gained so much influence over the horse, that
he would scarcely attend to any one else when I was about--Mr. von
Osten hardly excepted.
In this connection I would prefer to avoid the term "rapport," which
may rise in the minds of many, since it has been used so much in
connection with the phenomena of hypnotism, for I would not obscure
a fact that is clear by giving it a name that is vague.]
If the questioner knew the number of taps desired, (which was not the
case with the tests hitherto discussed), then the environment had still
less influence upon the horse--except that it caused occasional
interruption. The horse's responses, therefore, did not tend to become
more successful just because a number of persons were simultaneously
concentrating upon the result desired. This was proven by the
experiments which we repeatedly made for this purpose. Only one person
at a time had any influence upon Hans. If two questioners tried to
influence the horse at the same time,--other conditions being the
same,--success would be for the one who had the greater control over the
animal when working alone with him. Prof. Stumpf and I made the
following experiment. Both of us stood to the right of the horse, each
thinking of a number. In ten such tests Hans always tapped my number.
When Stumpf concentrated upon 5 and I upon 8, the horse responded with
8, i. e., the larger number. When Stumpf had 7 in mind, and I had 4, the
response would be 4, i. e., the smaller number. When Stumpf thought of
number 6, and I had fixed upon none, Hans tapped 35. He was evidently
awaiting my signal. When I went away Stumpf again demanded the number 6,
and the horse responded properly. When I returned, Stumpf's attempts
again failed. On another occasion Count Matuschka put a number of
questions, while Mr. von Osten stood behind him. All of the horse's
responses were correct, even the one answering the question: "How much
is 7 times 7?", which was difficult on account of the great number of
taps required. I was able to note from the direction of the horse's eyes
that he was attending only to his master and not to the Count. On still
another occasion Mr. Grabow sang two tones--the second being the fourth
of the first--and asked Hans: "How many intervals lie between?" I was
standing erect before the horse, and was thinking intently of the
number 2, but without giving any voluntary sign of any sort. Hans tapped
2, whereupon Mr. Grabow put a number of similar questions; but I no
longer thought of the answers, and all of Hans's responses went wrong.
Although Hans was not influenced by others so long as a suitable
experimenter was present, yet he might be disturbed and under certain
conditions might be led to make the back-step in response to certain
movements in his environment. The person to whom he responded would have
to be close to the experimenter and would necessarily have to execute a
movement greater in extent than the experimenter's. In such instances
the raising of the head, arm or trunk, was a sufficient stimulus. Thus
we made the following two series of tests. Mr. Stumpf stood with trunk
bent forward before the horse, and at a moment decided upon beforehand,
assumed an erect position. I myself stood beside Hans and asked him to
tap. When I stood at the horse's neck, then Mr. Stumpfs interruption was
effective. When I stood at the horse's flank, the interruption effected
only a seeming hesitation, and when I moved still farther back, the
horse continued to tap despite any attempted disturbance. In the second
series the questioner remained constantly at the right shoulder of the
horse, while the one who attempted to distract him, changed positions.
When the latter stood to the right immediately in front of or beside the
questioner, the disturbance was effective in 10 out of 13 cases. But
when he stood back of, and to the right of, the questioner, the attempts
at disturbance were seldom successful. If he chose a place before and to
the left of the horse, there was hardly any distraction (in 4 cases
only, out of 13), and if he stood to the left and behind the animal, he
exerted no influence whatever. Hans manifestly turned his attention,
almost exclusively, to the side at which the questioner stood.
That knowledge of this _modus operandi_ made it possible for those
persons to get responses from the horse, who hitherto had been
unsuccessful, is shown in the case of Mr. Stumpf when he began to
control his movements voluntarily on the basis of observations which had
been made.
_II. Problems which Hans solved by movements of the head._
We are here concerned with the horse's head movements upward, downward,
to the right and to the left, and also with nodding and shaking of the
head to signify "yes" and "no". We soon discovered that these
experiments, also, were successful without an oral statement of the
problem,--in other words, the auditory stimulus was quite superfluous.
The tests with the blinders showed that Hans was lost as soon as his
questioner was out of his view, but responded adequately the moment the
questioner was in sight. Hans, therefore, had established no idea of any
sort in connection with the terms "up", "down", etc., but in these
cases, likewise, he reacted in response to certain visual stimuli. The
nature of these stimuli I discovered at first in my observations of Mr.
von Osten and also of myself, when working with the horse.
Above all things it was necessary that the questioner, during these
tests, should stand perfectly erect. If he stooped ever so slightly, the
test was unsuccessful. If he carefully refrained from any movement
whatsoever, and looking straight before him asked the horse, "Which
direction is right?" or "Which way is upward?", Hans would execute all
sorts of head movements without rhyme or reason. It was evident that he
noted that a head movement of some kind was expected of him, but did not
know the particular one that was wanted. But if the questioner now
raised his head, Hans would begin to nod and would continue doing so
until the questioner lowered his head. This reaction was interpreted as
signifying "yes". Mr. von Osten had always asked Hans before each of the
more difficult tests whether he had comprehended the meaning of the
problem, and was reassured only upon seeing the horse's affirmative
response. But contrary to Mr. von Osten's expectation, Hans also
responded in this manner after a pair of ear-caps had been drawn over
his ears. In the case of the tests described at the beginning of the
chapter, in which the method was that of "procedure without knowledge",
Mr. von Osten had always insisted that we await Hans's nod of
comprehension before proceeding. We complied; Hans nodded and--regularly
disgraced himself!
When the questioner raised his head somewhat higher than normal, Hans
would throw his own upward, which was supposed to signify "upward". A
lowering of the head on the part of the questioner was followed by a
lowering on the part of Hans, which was his form of response for "down".
For some time I was in a quandary as to the difference between the
questioner's signal for this latter response and the one which was the
signal for the horse to begin tapping, although I had often given both
kinds unwittingly. Further experiments showed that Hans responded with a
nod of the head whenever the questioner, while bending forward, chanced
to stand in front of, or to the side of the horse's head, but that he
would begin to tap in response to the same signal, as soon as the
experimenter stood farther back. The difference in the two signals,
therefore, was very slight, and I repeatedly noted that instead of
tapping, as he had been requested, Hans would respond to the Count zu
Castell's and Mr. Schillings' questions by a nod of the head.
If, while standing in the customary position to the right of and facing
the horse, the questioner would turn his head a little to the right--a
movement which, when seen from the horse's position, would appear to be
to the left,--Hans would turn his head to his left. But if on the other
hand the questioner would turn slightly to the left,--i. e. seen from
the horse's position, to the right,--then Hans would turn his head to
his right. And finally, whenever the questioner turned his head first to
the right, then to the left, Hans would respond by turning first to his
left, then to his right. This, according to Mr. von Osten, signified
"zero" or "no". Since this movement could not be executed by the
experimenter while in a stooping position, it can now readily be seen
why it was that Hans, instead of shaking his head, always began to tap
whenever a placard with "O" upon it, was shown to him in the course of
the experiments in which the method was procedure without knowledge on
the part of the questioner. The latter expected the horse to tap, and
therefore bent forward. Like all of the horse's other forms of response,
this, too, was always unsuccessful whenever the questioner stepped
behind the animal. Although Hans had always responded to Mr. von Osten
and Mr. Schillings, and at first also to me, by means of the stereotyped
movement of the head to the right and then to the left to signify "zero"
or "no", I later succeeded in controlling my signals so as to get the
inverted order in the horse's response. In the case of Mr. Schillings
and of Mr. von Osten all of the movements just described were very
minute, and long after the movements, which were effective stimuli for
releasing the process of tapping, were recognized, it was still
exceedingly difficult to discover them in these two gentlemen. The
signal for "zero" and "no" was relatively the most pronounced of the
group in the case of Mr. von Osten, while with Mr. Schillings it was the
least pronounced, in comparison with his very strong "jerk". Yet in both
cases Hans responded with absolute certainty.
It is now readily conceivable how it was possible to make the horse
respond to all sorts of foolish questions, both by involuntary signs--i.
e., expressions following upon the bare imaging of the response
expected,--as well as by means of controlled signs. One could thus
obtain consecutively the answers "yes" and "no" to the same question. Or
one might ask: "Hans, where is your head?", and Hans would bend to the
earth. "And where are your legs?" He would look at the skies. Etc.
Let us examine for a moment the directives which the horse required for
the various positions. If one called him, while he was running about the
courtyard, he paid no attention whatever, but if one beckoned to him, he
came immediately. A raising of the hand brought him to a standstill. If
one now stepped forward or pointed one's hand in that direction, he
would step forward, or _vice versa_, he would step backward. By means of
minimal movements of the head, of the arm nearest the horse, or of the
whole body, Hans could be induced to assume the position one desired,
without touching him or speaking a word. I noticed this quite early in
the course of the investigation. Once, when intending to ask the horse
to step backward to the right, I inadvertently said "Step backward to
the left!", whereupon he stepped backward to the right. In spite of my
verbal error, I had involuntarily given him the proper directives.
Finally we may note that Mr. von Osten had occasionally asked the horse
to jump or to rear. The command in this case was: "Jump", or the
question was: "What do the horses do in the circus?". Since these tests
were just as effective when the command was given silently, it was an
indication that these, too, depended upon visual stimuli. What was
necessary to cause the horse to step backward and then jump forward was
to step backward oneself, or make a slight movement of the hand in that
direction. If one wished to make him rear, it might be effected by
throwing the arm or head slightly upward.
_III. Problems which Hans solved by approaching the objects to be
designated._
The method pursued in these tests was the following: From five to eight
pieces of colored cloth 1/2 x 1/4 meters in size were arranged in
changing series upon the ground, the interval between them being equal
to the width of one piece, or else they were hung upon a string a man's
height above the ground. This method was also employed when placards of
like size with written symbols were used. The horse stood ten paces away
and opposite the middle of the series, while Mr. von Osten stood at his
right. Hans was asked to go and point out the cloth of a certain color
or the placard with a certain word upon it. If the cloth lay upon the
ground, Hans picked it up with his mouth and carried it to the
questioner. If the cloth, like the placards, hung from the cord, he
approached, pointed it out with his nose and then backed up to his
original position. Before approaching the objects, Hans was required to
indicate, by tapping, the number of the place in the series (counting
from left to right), which the cloth or placard occupied. Mr. von Osten
never omitted this requirement. Then the command "Go!" was given, and
Hans obeyed. (As a matter of fact, a slight directive movement of the
head or hand was just as effective as the spoken command).
The following cases, chosen in a haphazard fashion, show that the
horse's indication of the object's place in the series, by means of
tapping, was by no means a guarantee that he would point it out
correctly. Five placards hung from the cord. Mr. von Osten asked: "What
is the position, counting from left to right, of the placard which has
the word 'aber' inscribed upon it?". Hans answered: 3. (It was indeed
the middle placard.) Then he was commanded: "Go!". Thereupon Hans went
straight to the fourth placard. On another occasion Hans happened to
drop a brown cloth upon a black one. His master asked him: "In which
place are there two cloths?". Hans responded correctly, "In the second
place". To the question "Which of the two is the black one?" he also
answered rightly: "The lower one". Upon being asked to get it, he
brought the white cloth.
The large number and the irregularities of the errors showed that there
was no manner of intelligence involved in the pointing out process. Thus
during the two months of our experimentation Hans was asked twenty-five
times by Mr. von Osten to bring the green cloth. Only six times did he
succeed in the first attempt, while in five instances he selected an
orange-colored cloth, four times a blue, three times a white one.
The fact that the errors were equally distributed over the tests with
the colored cloths and those with the placards is strong evidence that
the horse's response involved no intellectual process, for if that were
the case, then the responses in the tests with the placards would have
been very much more difficult, for they would have involved the ability
to read, whereas the tests with the colored cloths demanded only that a
few names be remembered. Nevertheless, the horse was as unsuccessful in
tests of one kind as he was in those of the other,--even when Mr. von
Osten acted as questioner. (50% failures in 78 placard tests; 46%
failures in 103 color tests.)
The fact that commands which were purposely enunciated poorly, or else
not spoken at all, were executed with just as much accuracy as those
given aloud, strengthened us in our supposition. On one occasion I
placed a blank placard with the others. When I ordered him to approach
_tabula rasa_, he invariably went to the right one. The following
illustrates how he fulfilled quite nonsensical commands. A series of
blue and green cloths lay upon the ground. Being asked where the black,
the orange, and the yellow cloths lay, Hans shook his head
energetically, i. e. they were not there. And yet, upon being asked to
bring them in the order named, he regularly brought one of the blue
ones.
All this goes to show that Hans did not know the names of the colors (to
say nothing of the symbols on the placards). It was plain that here
also, as in all the other cases, he was controlled by signs made by the
questioner, the nature of which I soon discovered. Standing erect, Mr.
von Osten always turned head and trunk in the direction of the cloth or
placard desired. Hans, keeping his eye on his master, would proceed in
that direction. Even after he had already started out, thanks to his
large visual field one could control his direction by turning slightly
more to the right or to the left. If, however, he had already arrived at
the row of placards or cloths, this method ceased to be effective, for
then he could no longer see the experimenter. It made no difference
whether the cloths lay on the ground, or were suspended, like the
placards.
The following fact justifies the conclusion that the bodily attitude of
the questioner was the effective signal. The more numerous the cloths,
or the nearer they were placed together, the more difficult one would
expect it to be for the horse to select the one indicated by the
experimenter. Such was indeed the case, for the number of errors
increased with the number of cloths presented.
But no matter how many cloths there might be, or how closely they might
be placed, it was always possible to indicate either end of the row, for
in that case one had merely to turn to the extreme left or the extreme
right, and might even turn beyond the row. Hans seldom failed in these
cases, whereas he made many errors when cloths or placards within the
series were wanted.
To turn from the nature and number of Hans's errors, to their
distribution,--observation proved the hypothesis that the nearer two
cloths lay together, the greater was the chance of their being mistaken
one for the other. If we designate as "error 1" all those cases in which
Hans went to cloth II instead of to cloth I, cloth III instead of cloth
II, to V instead of IV, etc., and as "error 2" when he mistook III for
I, IV for II, in fine, whenever he went two places too far to the right
or left, and as "error 3" whenever he went three places too far to
either side of the cloth desired, we find the following grouping of
errors:
With Mr. von Osten, a total of 63 errors:
73% "error 1"
21% "error 2"
4% "error 3"
1% "error 4"
1% "error 5"
With Mr. Pfungst, a total of 64 errors:
68% "error 1"
20% "error 2"
11% "error 3"
1% "error 4"
0% "error 5".
The most frequently recurring error, therefore, was the one in which the
horse, instead of going to the cloth desired, approached the one
immediately adjacent. On page 79 I said that Hans's errors were without
system, but only in so far as it was impossible to explain them on a
basis of the colors which seemingly were mistaken one for the other. A
part of a series in which Mr. von Osten acted as questioner may serve as
an illustration. The order given is that of the experimental series as
it occurred. Five colored cloths were used.
Color of the cloth
asked for: blue, brown, brown, brown, brown, brown, green, green.
| | | | | | | |
brought: orange, orange, green, green, yellow, green, blue, orange.
Place of cloth
asked for: V II II II II II III III
| | | | | | | |
brought: IV IV III III I III V IV
The interpretation of this series which it would be hard to explain by a
reference to the colors which were mistaken, is simply this: Cloths
lying near together were regularly mistaken on the part of the horse.
Experimental control of the questioner's movements decided the question.
If the questioner at first indicated the proper direction and then
turned about after the horse had already started forward, he was as a
rule misled. When the questioner did not face the cloths at all, but
turned away at right angles, or when he turned his back upon them, Hans
was completely at sea. If, on the other hand, the cloths were arranged,
not in a row, but in several heaps, so that one might turn to a
particular heap, but could not indicate a particular cloth, then Hans
would regularly go to the proper heap, but would always bring forth the
wrong cloth. After much persuasion Mr. von Osten consented to make a
series of these tests himself. Hans's failures were deplorable. He would
take up first one cloth then another, turn again to the first, etc. We
would mention, however, that this apparent searching was not done
spontaneously, but in response to Mr. von Osten's calls, such as "See
there!", "The blue!", etc. Every time Mr. von Osten called, Hans would
drop the cloth he was holding in his mouth, or he would turn away from
the one he was about to grasp, and would then try another one.
In addition to these visual signs, the horse received auditory signals
in these tests, (as in all others in which he was required to bring
objects). As soon as the questioner noticed that Hans was about to take
up the wrong cloth, all that was necessary to make him correct his error
was to give some sort of an exclamation, such as "Wrong!", "Look, you!",
"Blue!", etc. Hans would pass on as long as the calling continued. If
he was picking up, or about to pick up, a cloth when the exclamation was
made, he would go on to the next; but if, at the time he was on his way
to a certain cloth, he would change his direction in response to the
call. If he stood before one of the pieces at the time, but had not
lowered his head, he would pass on to the next. In all this he would
adhere to a certain routine of procedure. If he was approaching a series
from the right, then a call would cause him to turn to the left, if he
was coming from the left, he would turn to the right. If he had
approached the row of cloths near the center, he would turn, in response
to the questioner's calls, to the left,--seldom, very seldom, to the
right. Mr. von Osten did not seem to be able to control the responses of
the horse, entirely. As a rule, but not always, one call sufficed to
make Hans pass on to the next cloth. If too many calls were given, he
would often go too far. Loud exclamations were superfluous.
These statements are not mere assertions, but are founded upon the
records of the results. The tests in which calls were made show a larger
percentage of correct responses than do those without calls. Of a total
of 103 tests with colored cloths, which Mr. von Osten performed for us,
only 37% brought forth successful responses on the part of the horse
when visual signs were the only directives and when there were no
directions by means of calls, whereas the total percentage of successful
responses was 54%, if we add to the above those in which the vocal
exclamations helped to bring about success. The corresponding
percentages for the total of 78 tests with the placards were 23% and
50%. In a total of 110 color tests I myself obtained 31% correct
responses under the first head, and 56% under the second head. In a
total of 59 tests with placards I succeeded in getting 31% correct
responses under the first head and 46% under the second head. We must
note that without verbal admonition only one-third of the tests brought
forth correct responses, whereas one-half succeeded when those in which
calls were used, are added. Still, this is a relatively poor showing. In
the most favorable series that Mr. von Osten ever obtained in our
presence--and there was only one such--50% of the responses 'without
admonition' were correct, and 90% when all the correct reactions, both
with and without admonition, were taken into account.
Not all the places in the row required the same amount of assistance by
means of calls. Those positions which needed the most help, were those
which it was most difficult to indicate to the horse by the visual sign,
i. e., the attitude of the questioner's body. We noted above (page 81)
that the cloths at either end of the row were less difficult to point
out than those nearer the middle. If our hypothesis holds true, we would
expect that the end cloths would involve fewer auditory signals in the
process of pointing out, and those within the row a greater number of
such signs. By way of illustration, I will cite one series of tests in
which Mr. von Osten was questioner, chosen not because it is most
conformable to my hypothesis but because it is the longest (48
consecutive tests with five cloths) which I have. In the upper row I am
placing the successful responses without auditory signs, in the lower
those involving both auditory and visual signs.
Place of the cloth : I II III IV V
No. of sucessful } visual signs only : 5 2 1 2 4
responses. } visual and auditory signs : 5 5 8 5 5
We see that without verbal admonition the first and last places are most
favorable for success, the second and fourth far less, and the middle
least favorable. These differences disappear when admonitions are
introduced, for all of the places then have the same number of correct
responses with the exception of the middle, which now has even more than
the others.
One more experiment which I made will close the discussion. The
following colors were placed from right to left: orange, blue, red,
yellow, black, green. I turned my back upon them, and therefore could
guide the horse by verbal commands only. I asked him to bring the
orange. Hans approached the yellow. I now called three times, allowing a
short interval between the calls. At the first "Go!" he passed from the
yellow to the red, at the second from the red to the blue, and at the
third from the blue to the orange, which he then proceeded to pick up
and bring to me. I had noted this same thing in Mr. von Osten's tests,
although there, there were often other factors entering in. By
exercising the utmost precision in facing the cloths, and by using, in
addition, suitable oral signs, I succeeded in getting Hans to bring,
successively, each one of the six cloths in the row, and without a
single error,--and all this in the presence of Mr. Schillings who did
not have the slightest notion of the secret of my success.
We need hardly say, in passing, that all that was true of the tests with
colored cloths, was also true of the tests in which the placards were
used. It was all the same to the horse whichever was placed before him.
We have thus tested all of the horse's supposed achievements. None of
them stood the critical test. It would have been gratifying to have
repeated some of the experiments and to have made Hans the object of
further psychological investigations, but unfortunately he was no longer
at my disposal after the publication of the report of the
December-Commission. Some may say that we have had almost enough of a
good thing, but we must bear in mind that many of the tests which were
carried out,--such as those in which the method was that of "procedure
without knowledge", those in which the ear-muffs were used, those in
which distractions were introduced,--had previously been made by other
persons (see pages 41f, 45, 63), and with other results, than ours. A
more thorough test, therefore, would have been doubly desirable.