EXPLANATION OF OBSERVATIONS 149 



Another group of errors was characterized as-At ub- 

 bornn ess on the pajrt, of Jians, such as his persistence in 

 repeating an incorrect response, or his repetition of a 

 former correct answer in response to later questions 

 where it was perfectly senseless. During a demonstration 

 before a large number of persons, I held a slate with the 

 number 13 upon it within the horse's view and also 

 within view of the spectators. I, myself, did not know 

 what number was written on the slate. Having been 

 asked to tap the number, Hans responded by tapping 

 5. The grand-stand shouted " Wrong ! " I asked Hans 

 to try again. Four times in succession he answered 5. 

 At another time Mr. von Osten and I each whispered a 

 number (7 and i, respectively,) into the horse's ear and 

 asked him to add the two. Three times in succession he 

 tapped II. After the test had been repeated in accord- 

 ance with " procedure with knowledge " and a correct 

 response had been received, we tried once more a test of 

 " procedure without knowledge ". Again, he responded 

 with an 11. On a third occasion, I asked Hans to tap 5. 

 He responded with a 4 and then, correctly, with a 5. 

 Thereupon, I asked him to tap 6. Again, he responded 

 with a 4. Then I asked him to tap 7. Once more he re- 

 sponded with a 4, and only when I proceeded to count 

 aloud did he tap 7 correctly. I had him repeat the 7 and 

 then went over to 9. Promptly he responded with an- 

 other 7. In these cases, which by-the-way were not very 

 frequent, we have to do, not with stubbornness on the 

 part of Hans, but with the persistence of that number 

 in the consciousness of the questioner. Modern psy- 

 chology has recognized this tendency of ideas, which 

 have once been in consciousness, to reappear on other 

 occasions even though they are wholly inappropriate. 



