EXPERIMENTS AND OBSERVATIONS 39 



coins. Hans plainly was incapable of the astonishing 

 feats of memory which had been claimed for him. 



Finally we investigated Hans' musical ability. In a 

 room adjoining the horse's stall there was a small har- 

 monica, which spanned the once accented octave. On this 

 one or more tones were played. The horse was required 

 to indicate the tone played, the number of tones played 

 and their relation to one another. For testing his general 

 hearing 20 tests were given in which the method was pro- 

 cedure without knowledge. Of the responses only one 

 was correct, and that one was the tone e, for which the 

 proper response was three taps, but we must bear in mind 

 what has already been said of the number 3. The tone 

 b was indicated by 11 taps, although Hans had only 

 learned a scale of one octave and therefore could respond 

 to only seven tones. In the tests in which the method 

 was procedure with knowledge, he again, without excep- 

 tion, was successful. Similar results were obtained in the 

 analysis of compound clangs. In the cases of procedure 

 without knowledge (although the experimenter here 

 knew the correct responses, he purposely refrained from 

 thinking of them) not a single response was correct; 

 while in the cases of procedure with knowledge, all but 

 one were correct. The following were typical re- 

 sponses: Three tones were played and the question was 

 asked, " How many tones were played ? " Hans re- 

 sponded first with 4 taps and then with i. The tones 

 c, e, g, a, (i, 3, 5, 6) were struck and the question asked, 

 " Which tone must be eliminated to make the complex a 

 chord?" In the tests in which the method had been 

 procedure with knowledge, this question had always been 

 answered correctly, but when procedure was without 

 knowledge the responses were first 13, a tone which does 



