32 THE HORSE OF MR. VON OSTEN 



tained in single trials, could not claim objective validity, 

 even though the persons making the tests were subject-; 

 ively convinced. 



The course of the experiments was determined by the 

 nature of the problem itself. By means of a very simple 

 test it was possible to discover whether or not Hans was 

 able to think independently. He was confronted with 

 problems in which the procedure was without knowledge" 

 of the answer on the part of the questioner. If under" 

 these conditions he could respond with the correct an- 

 swer — which could be the result of a rational process 

 only — then the conclusion that he could think independ- 

 ently, was warranted. The examination would be closed 

 and Mr. von Osten would be justified in all he claimed 

 for the horse. If, however, Hans should fail in this test, 

 then the conclusion that he could think was by no means 

 warranted, but rather the inference that he was dependent 

 upon certain stimuli received from the questioner or the 

 environment. Further investigation would be for the pur- 

 pose of discovering the nature of these stimuli. 



To ascertain by means of which sense organ or organs 

 the horse might receive these necessary stimuli, the 

 method of elimination was employed. We began by ex- 

 cluding visual stimuli by means of a pair of very large 

 blinders. Should this investigation be without results, 

 then we would proceed to test the sense of hearing. The 

 elimination of auditory stimulations would be more diffi- 

 cult, because ear-caps or the closing of the passage by 

 means of cotton would not give sufficient assurance that 

 the sound-waves were being interrupted, even if the horse 

 were docile enough to sufifer these appliances. There- 

 upon would follow the testing of the sense of smell and 

 of the skin-senses. And finally there might be involved 



