EXPERIMENTS AND OBSERVATIONS 33 



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 cir- 

 cumstances 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 ques- 

 tioner 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 * — 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 al- 

 lowed 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 fre- 

 quently 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 



* The expressions questioner and experimenter are used interchange- 

 ably in this treatise. 



