The entry says that thirteen men watched Wilhelm von Osten for two days and found no signal, and that three men with a canvas tent and a pack of cards found, a month later, that there had never been anything else. This piece gives the first inquiry in the detail the entry has no room for: how the commission came to exist, who sat on it, what its own record says it did, the words of the statement, and the week of comment that followed. The documents are Stumpf’s, printed as Supplements II and III of Pfungst’s book, in Carl Rahn’s English of 1911; the newspapers are as Karl Krall reprinted them in 1912, translated here.

How it came to exist

By the last week of August 1904 the horse had been in the papers for seven weeks and von Osten had been accused in print of a deliberate fraud. He had petitioned the Kaiser for an official inquiry, and the petition had gone to the Prussian Ministry of Education, whose official Professor Norrenberg had written to him that Stumpf considered the case “truly the most astonishing thing that has ever occurred in animal pedagogy”. Stumpf wrote to von Osten on 14 August that “I am now of your opinion that an official commission would have to be appointed”, and advised him to ask the Academy of Sciences for one. Nothing came.

On 2 September Schillings gave up waiting. In the Berliner Tageblatt he announced that von Osten, disappointed in his hope of a commission, was meeting “an unobjective criticism of a kind never before seen in public”, and that “under these circumstances we shall proceed to appoint a private commission of respected scholars and unprejudiced men, which will first, by a preliminary examination in a strictly scientific manner and with every possible precaution, assemble material on this case which, when published, may perhaps give occasion for a subsequent official examination”. The next day Stumpf, in the Tag, supported the idea, said what its first task must be, “to judge the presence of aids in the ordinary sense of the word, and also of involuntary signs”, and added that “the scholars must be joined by horse experts, or by men who are both at once.”

The press noticed who was choosing the members. “There can be no question of an ‘independent’ commission,” the Freie Deutsche Presse wrote on 9 September, “if only because Herr von Osten and his following choose the members themselves and do not shrink from choosing men who have linked their names and their reputations as scholars with the Hans affair for months or weeks.” The Kölnische Volkszeitung called it a panel drummed together by “the Hans syndicate” and said the best advertisement for a learned horse was the opinion of a scientific commission. Albert Moll, the chairman of the Berlin Psychological Society, who had run his own tests on the horse in June 1903 and come away certain it was responding to signals, had written twice to von Osten in August proposing a few trials under strict conditions and had been ignored.

Who they were

The signatures on the statement of 12 September, with the descriptions the signatories gave themselves:

• Paul Busch, circus manager, Royal Prussian Kommissionsrat. The proprietor of the Circus Busch, who had tried that summer through his manager to engage the horse and been refused.
• Otto, Count zu Castell-Rüdenhausen, retired captain. He had worked with the horse for weeks; Stumpf thanked him in the book for “his frequent intercession on our behalf with the owner of the horse”.
• Dr A. Grabow, retired member of the school board, who had published his own successful tests in the Zeitschrift für Pädagogische Psychologie.
• Robert Hahn, municipal teacher, whose long report in the Kölnische Zeitung of 13 August was the first that Krall read.
• Dr Ludwig Heck, director of the Zoological Garden, who had known of the horse for two years and avoided it “as long as I could”.
• Dr Oskar Heinroth, assistant at the Zoological Garden.
• Dr Richard Kandt.
• Major F. W. von Keller, retired, who had known von Osten for fifteen years and whose written statements Stumpf used as evidence that the method of instruction was not invented after the fact.
• Major-General Th. Köring, retired.
• Dr Miessner, assistant at the Royal Veterinary College.
• Professor Nagel, head of the department of sense-physiology at the Physiological Institute of the University of Berlin.
• Professor C. Stumpf, director of the Psychological Institute, member of the Academy of Sciences.
• Henry Suermondt, whom Pfungst calls “the distinguished horseback rider”.

Zobel, the major-general who had written the first article, was not among them, and neither was Schillings, whom the public had begun to doubt.

What they did

Stumpf abstracted the record a few days afterwards from the minutes von Hornbostel kept, and showed it to a small circle; the commission had decided to publish no particulars “until some positive statement might be made.” The abstract was printed for the first time in Pfungst’s book, as Supplement III. The decisive sessions were on 11 and 12 September and lasted four hours each.

The first difficulty was von Osten’s own. He had laid down “that we were to work without him from the very beginning”, so that nothing could be laid to him. Schillings had already met the condition once, “a man whose fairness ought to be doubted by none”, who had come “utterly skeptical” and within a week could get answers regularly; “however, since the public had begun to doubt Mr. Schillings also, another person had to attempt the role of questioner.” Castell tried, and practised for some days, “but his success—although of no small moment—was not great enough to be convincing.” Telling von Osten so “caused a veritable catastrophe. He declared in a most decisive manner that he would have to insist upon the condition he had imposed, since the public demanded it, and he could never assist in any tests, until he had been cleared of the suspicion of having descended to the use of tricks. If it should take weeks to accustom the horse to a new questioner, there would be no alternative but to wait that length of time.”

What saved the sitting was a mare. “We had chanced in our discussion to mention the experience of Dr. Miessner, a member of the commission, who on the day before had gone to witness an exhibition of the mare ‘Clever Rosa’, and who believed that he had succeeded in discovering the tricks involved.” Rosa was being shown at Castan’s Panopticum as the rival of Clever Hans; Stumpf, who sat to one side at her performance, saw the signal every time, a forward bend of her exhibitor’s trunk after standing bolt upright, invisible from the front, where the audience sits. “There was a sudden change in Mr. von Osten’s attitude. He expressed his willingness to undergo the most stringent examination and agreed to anything in the way of conditions of control, challenging even the proven ability of Dr. Miessner. ‘I have neither whip nor rod, as had the man in the exhibition, and agree to any precautionary measures you may care to take.’”

So they watched him. “After he had gone, the commission decided to ask him to have the horse perform one of the more common, simple, feats. They were going to watch him very closely. Different members were assigned the task of attending to different parts of his body (head, eyes, right hand, left hand, etc.) while Mr. Busch, since he was the most proficient in the detection of tricks, was to regard the total behavior of the man.” The feats were the day of the week, the day past and the day ahead, the date, arithmetic, and counting rings on a rod; Grabow and Hahn put a few questions themselves. “All tests were successful. Mr. von Osten withdrew, and in comparison of notes which followed, Mr. Busch, as well as all the others, declared that they had discovered nothing of the nature of a visible sign. Mr. Busch said that he had also kept an eye on the spectators and had noticed nothing there.”

Busch then asked to see von Osten work the horse with no one else present. The tests were the coloured cloths, which the horse had first to place in the row by tapping and then fetch in his mouth; the approach to the one of five gentlemen whose photograph had been shown him; and spelling “Rat” and “Busch” on the letter table. “Nearly all of these tests were likewise successful. In the conference which followed, Mr. Busch again declared that he had noticed no trace of a sign; he maintained that, in the selecting of colored cloths (especially when they were placed so closely together) and in the approach toward a person, there was no possibility whatever that some trick was being used.”

On the 12th von Osten agreed to two arrangements. In the first, another man questioned the horse while “Mr. von Osten himself was to stand, back to back to the questioner and to bend forward, so that he was effectually hidden from the horse’s view, yet could, by means of occasional calls, make his presence known to the animal.” Hahn and Castell asked simple sums; when von Osten went into the stable, Castell had the horse count persons and windows, “all of which were solved correctly.” Between the two series the names of six members were written on six slates and hung on a string, von Osten pointed to a man and asked on which slate his name stood, and “the correct number was tapped in every case”; the horse also walked to the slate, “although this was not as uniformly successful as tapping.” Busch “declared that the feats appeared inconceivable to him; and again none of the men had noted anything in the way of signs.”

The second arrangement was the one that mattered, and it was tried last. “Another man in Mr. von Osten’s absence was to ask the horse to tap a certain number. Then the questioner was to leave, and Mr. von Osten, returning, was to ask the horse to perform some arithmetical process with the number which was thus unknown to the master. Mr. von Osten said that he thought that this method was somewhat risky, since the horse would be aware that he, Mr. von Osten, did not know the number, and might therefore be in a humor to play some prank.” To be sure of getting answers, Schillings was fetched to give the numbers; von Osten went into the house with a member of the commission; Schillings left before the second half of each test without meeting him. “Five tests were made in this way. They were not attended by such amazing success as were the preceding ones, but nevertheless the results were surprising. The horse nearly always repeated the number itself, instead of performing the operation required. Since, however, Mr. Schillings, owing to a misunderstanding, had, in the first two cases, said to the horse: ‘You are to repeat this number for Mr. von Osten’, the errors might appear to be a result of this request.”

Pfungst, going over this later, thought the repeated number might have been in the memory of someone present who had worked with the horse, and that chance might have played a part. Castell’s forty correct answers in eight days, “among them some in regard to which he himself had been momentarily in error”, were weighed at the final discussion, and so were the members’ memories of other people getting answers in the absence of both von Osten and Schillings, and Stumpf’s written account of the method of instruction. “None of the tests witnessed could be referred to chance or to the use of tricks.” The commission “limited itself, however, to the purely negative side—principally in denying the use of tricks,—and expressed no opinion with regard to the actual genesis of the horse’s accomplishments, since it believed that there was great possibility that other factors were involved which ought to be carefully investigated.”

The statement of 12 September 1904

“The undersigned came together for the purpose of investigating the question whether or not there is involved in the feats of the horse of Mr. von Osten anything of the nature of tricks, that is, intentional influence or aid, on the part of the questioner. After a careful investigation they are unanimously agreed that such signs are out of the question under the conditions which were maintained during this investigation. This decision in no wise takes into account the character of the men exhibiting the horse, and who are known to most of the undersigned. In spite of the most attentive observation, nothing in the way of movements or other forms of expression which might have served as a sign, could be discovered. In order to obviate involuntary movements on the part of those present, one series of tests was made with only Mr. Busch present. Among these tests were some in which, according to his professional judgment, the possibility of tricks of the sort commonly used in training, was excluded. Another series of tests was made in such a way that the correct answers to the questions which Mr. von Osten put to the horse, were unknown to the questioner. From previous observation the greater number of the undersigned also know of a large number of cases in which, during the absence of Mr. von Osten and Mr. Schillings, other persons were likewise able to obtain correct responses from the horse. Among these were some cases in which the questioner did not know the correct solution of the problem or was mistaken about it. And lastly, several of the undersigned have become acquainted with the method which Mr. von Osten used, which has little in common with methods of training, and is patterned after the instruction given in the elementary schools. As a result of these observations the undersigned are of the opinion that unintentional signs of the kind which are at present familiar, are likewise excluded. They are unanimously agreed that this much is certain: This is a case which appears in principle to differ from any hitherto discovered, and has nothing in common with training, in the usual sense of that word, and therefore is worthy of a serious and incisive investigation.”

Stumpf’s gloss on the sentence about unintentional signs, written in 1907, is that it “could only be interpreted as follows: that signals of the kind that are used intentionally in the training of horses, could not have occurred even as unintended signs, for otherwise Mr. Busch would have detected them. And in order to be observed by him it was immaterial whether they were given purposely or not.” He added a footnote for those who had read the sentence as a denial that any visual signs could exist: “What I did deny, and still deny, is that up to that time any had been proven to occur.”

The week after

The Sportwelt of 14 September told its readers what it had heard was the experiment that decided the commission: that in von Osten’s absence Schillings had put to the horse sums set by members and left, that von Osten had then come back and received the answers, “which were in the majority correct”, and that “this astonishing fact must indeed convert the strongest doubters, as it filled the gentlemen of the commission with enthusiasm.” The record says five tests, the number repeated, and a misunderstanding. The Berliner Tageblatt of the same day: “Two hold better than one. Clever Hans cannot come to rest and will set yet another commission in motion. Now the purely scientific question, whether Hans thinks ‘independently’, will be investigated.” The Reichsbote: “The Clever Hans scandal goes on, and the ‘scholars’ go on merrily making fools of themselves.”

On 15 September Stumpf sent the members a circular. “In case questions about details of our investigation reach you, I ask you not to enter into any information, but only to insist that our task was solely to exclude tricks, that in doing so we naturally also paid attention to involuntary influences and perceived none. Everything further, every positive explanation, lay outside our intention. We must absolutely decline to give an account of the details of the tests. That they were carried out to the best of our knowledge and conscience, our names must vouch. Whoever is not satisfied by that may go on doubting.” On the 22nd the Frankfurter Zeitung printed an interview in which Stumpf said of the signs: “We were so careful as to write in our declaration that conscious means of training on the part of the horse’s teacher are completely excluded—the unconscious ones, however, only so far as they belong to those hitherto known to us!”

Moll’s verdict, given to the Psychological Society on 20 October and printed in his journal, was that the commission had erred, “and the error has been so grave in its consequences because the supposedly reckoning horse made such a stir at the time and a well-known professional psychologist let himself be led into one of the most absurd opinions ever issued”; that its chairman “did not see the most important thing; the most important thing was the fact that signs were given to the horse”; and that “everyone sees what he wants to see. … It is exactly the same as with conjuring, where the very cleverest always believe that they have seen everything, while in reality everything essential escapes them. Let no one be in the least impressed by authorities!” Stumpf, who had the horse in a tent by then, did not reply in print. His answer was the report of 9 December, which is the next companion piece.

Sources

• Oskar Pfungst, Clever Hans (The Horse of Mr. von Osten), translated by Carl L. Rahn, New York: Henry Holt, 1911: Stumpf’s introduction, pages 1 to 14, and Supplements II and III, pages 253 to 260. The statement and the abstract of the records are quoted from this translation. archive.org
• Karl Krall, Denkende Tiere, Leipzig, 1912, pages 285 to 318: Norrenberg’s letter and Stumpf’s letter of 14 August as the Berliner Zeitung printed them on 20 August 1904; Schillings in the Berliner Tageblatt of 2 September; Stumpf in the Tag of 3 September; the Freie Deutsche Presse of 9 September; the Kölnische Volkszeitung of 8 and 15 September; the Sportwelt and the Berliner Tageblatt of 14 September; the Reichsbote of 10 September; Stumpf’s circulars of 3 and 15 September; the Frankfurter Zeitung interview of 22 September; and Moll’s statement of 20 October 1904 in the Zeitschrift für Pädagogische Psychologie and in Der Hypnotismus. Translated here by the author of this entry. archive.org
• The New York Times, 14 September 1904, the cable on the commission’s statement. archive.org
• The Washington Times, 13 November 1904, page 24, on Moll’s address and his unanswered letter. loc.gov