EXPERIMENTS AND OBSERVATIONS 31 



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 re- 

 sults 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 condi- 

 tions of experimentation were such that the further con- 

 tention that he happened to be tired or otherwise indis- 

 posed, 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 ob- 



