EXPLANATION OF OBSERVATIONS 153 



in establishing Hans's reputation, nothing has brought 

 him so many followers, as these cases in which he, rather^ 

 than his mentor, has been in the right. Compared with 

 the mass of cases in which Hans was wrong these latter 

 cases are diminishingly few in number, yet these few 

 made such an impression upon the observers that their 

 number tended to be overestimated. As a matter of fact, 

 I have been able to discover records of only seven 

 such cases. Two of these were reported by the Count 

 zu Castell. On the 8th of September, he entered the 

 horse's stall, alone, and believing it to be the seventh 

 day of the month, he asked Hans the date. The horse 

 responded correctly with 8 taps. At another time he 

 held up before Hans a slate on which were written the 

 numbers 5, 8 and 3 and asked the horse to indicate their 

 sum which in the momentary excitement, vaguely ap- 

 peared to Castell to be 10. To his chagrin he noticed 

 that Hans continued to tap. Thereupon he intentionally 

 remained motionless until the horse had stopped tapping 

 spontaneously — as he thought — at 16. (The newspapers 

 reported that the numbers to be added had been 5, 3, and 

 2; that the questioner had expected the answer 11, but 

 that Hans had in three tests always ceased tapping at 

 10.) In both cases the questioner regarded the answers 

 of the horse as wrong and recognized his mistake when 

 his attention was called to it. I, myself, had the same 

 experience. One time I received in response to the ques- 

 tion, " What day of the week is Monday ? ", the answer 

 2, although I had expected the answer i ; at another time 

 I asked, "How much is 16 less 9?", and the horse re- 

 sponded with 7 taps, although I had erroneously expected 

 S- I noticed my mistake only when my attention was 

 called to it by one of those present. Another example is 



