74 THE HORSE OF MR. VON OSTEN 



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 move- 

 ments 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 ex- 

 periments, also, were successful without an oral state- 

 ment 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 ques- 

 tioner 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, like- 

 wise, he reacted in response to certain visual stimuli. The 

 nature of these stimuli I discovered at first in my observa- 

 tions of Mr. von Osten and also of myself, when working 

 with the horse. 



Above ^11 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 



