[By James R. Angell] The University of Chicago It gives me great pleasure to accept the invitation of the publishers to write a word of introduction for Mr. Rahn's excellent translation of "Der Kluge Hans", a book which in the original has been but little known to American readers. The present wave of interest in animal life and behavior renders its appearance peculiarly appropriate. No more remarkable tale of credulity founded on unconscious deceit was ever told, and were it offered as fiction,

[By C. Stumpf] A horse that solves correctly problems in multiplication and division by means of tapping. Persons of unimpeachable honor, who in the master's absence have received responses, and assure us that in the process they have not made even the slightest sign. Thousands of spectators, horse-fanciers, trick-trainers of first rank, and not one of them during the course of many months' observations are able to discover any kind of regular signal. That was the riddle. And its solution was fo

If we would appreciate the interest that has been aroused everywhere by the wonderful horse solving arithmetical problems, we must first consider briefly the present state of the problem of animal consciousness. [C] Animal consciousness cannot be directly gotten at, and the psychologist must therefore seek to appreciate it on the basis of the animal's behavior and with the assistance of conceptions borrowed from human psychology. Hence it is that animal psychology rests upon uncertain foundation

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

In the preceding chapter we asked: What is it that determines the horse's movements? Independent thinking, or external signs?—We found that it was solely external signs, which we described as certain postures and movements of the questioner. Beyond a doubt these necessary signs were given involuntarily by all the persons involved and without any knowledge on their part that they were giving any such signs. This is to be seen from their statements, which cannot be cavilled at, as well as from the

The tests which are to be briefly reported here, were begun in November, 1904, and were carried out at the Psychological Institute of the University of Berlin. The purpose was twofold: first, to discover whether the expressive movements noted in Mr. von Osten, Mr. Schillings, and others, were to be regarded as typical and to be found in the majority of individuals,—and secondly, to ascertain in how far the psychical processes which I had noted in my own case and which I believed to lie at bottom

The author having described the observations made upon the horse, and having discussed the activities of the questioner upon the basis of observations made objectively and upon his own introspections, and having verified the results thus obtained, by means of laboratory tests,—we are now in a position to solve satisfactorily all the problems which this interesting case has presented. That which is least difficult to understand is the horse's seeming knowledge of language and particularly his abi

In the preceding discussion we have regarded the achievements of the horse as well as Mr. von Osten's explanation of them, as matters of fact. Let us now consider the question: How did the horse come by these achievements, and how did its master arrive at his curious theory in explanation of them? Did he indeed seek to instill in the horse's mind the rudiments of human culture through long years of painstaking instruction in accordance with the method described in Supplement I (page 245) ? If th

If we would make a brief summary of the status of Mr. von Osten's horse in the light of these investigations and try to understand what is the bearing upon the question of animal psychology in general, we may make the following statements. Hans's accomplishments are founded first upon a one-sided development of the power of perceiving the slightest movements of the questioner, secondly upon the intense and continued, but equally one-sided, power of attention, and lastly upon a rather limited mem

[By C. Stumpf] The following is a report of the account, which Mr. von Osten gave Professor Schumann and me, of the method which he had used in the instruction of the horse, and which was illustrated by actual demonstrations. I cannot testify, of course, that Mr. von Osten really did adhere to this method throughout the four years in which he tutored the horse, but I will say that I have several good reasons for believing that it was impossible for him to have trumped up this make-believe scheme

"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 exhibi

The important meetings occurred on the 11th and 12th of September and both of them extended over four hours. The greatest difficulty was occasioned by the condition laid down by Mr. von Osten: that we were to work without him from the very beginning. In a certain sense this condition had been met once before when Mr. Schillings appeared upon the scene, a man whose fairness ought to be doubted by none. He came utterly skeptical, and yet in the course of a week he learned to handle the horse and r

Together with Dr. E. von Hornbostel and Mr. O. Pfungst, I have tried during the past few weeks to find an explanation of the accomplishments of the horse 'Hans' by the experimental method. We had access to the horse in the absence of the master and groom. The results are as follows: The horse failed in his responses whenever the solution of the problem that was given him was unknown to any of those present. For instance, when a written number or the objects to be counted were placed before the h

(The names of the authors of anonymous works are placed in parenthesis.) New Edition. By James Rowland Angell , Professor and Head of the Department of Psychology in the University of Chicago. Fourth Edition, Revised and Enlarged. ix+468 pp.  8vo.  $1.60. The fourth edition contains a large amount of new material, chiefly empirical in character. To offset this addition, many of the more strictly theoretical discussions have been condensed. The old material has been rearranged and many new drawin

(Prospectus of entire Series on request) By R. W. Doane , of Stanford University. Illustrated. $1.50 net; by mail, $1.62. "Describes lucidly and entertainingly, in language that all may understand, the discoveries in the disease-bearing qualities of insects, the successful fights that have been made in consequence against yellow fever, malaria and plague, and the present state of the investigations."— New York Sun. By B. E. Fernow , of the University of Toronto. Illustrated. $2.00 net; by mail,