THE AUTHOR'S INTROSPECTIONS 99 



forms of expression? If we might assume that the ques- 

 tioner always had in mind the movement he awaited on 

 the part of the horse, and never thought of " zero " or 

 " no ", then the contradiction would solve itself. But I 

 must deny decidedly that I ever thought of the movements 

 of the horse's head, and Mr. Schillings, whom I ques- 

 tioned on this point, agreed with me in this, in so far as his 

 own mental processes were concerned. I can see nothing 

 for it but that in this instance the expressive movements 

 normally connected with the concepts " zero " and " no " 

 have been replaced by other forms, without the questioner 

 becoming aware of it. That such displacements may 

 occur, has been shown by the tests described on pages 107 

 to 112. That they did occur in this instance may be 

 concluded from the following observation. In respond- 

 ing to me, as well as to Mr. Schillings, Hans always 

 moved his head first to the left, then to the right, never 

 in the opposite order. That this was not a peculiarity of 

 the horse, but must be ascribed to the signs which were 

 given him, is shown by the possibility of inverting the 

 order under experimental control (page 77). Frequently 

 Mr. Schillings and I had seen the horse respond to his 

 master by means of such head-movements, and the order 

 was always, without exception, the one mentioned. It 

 must be assumed therefore that the horse's movement, 

 which we so often noticed, made such an impression upon 

 us, that afterwards it was regularly reproduced on our 

 part quite unconsciously, so that Mr. Schillings never, and 

 I only after a long time, became aware of the whole 

 process. 



In closing, just a word as to the discovery of our own 

 movements. I soon noticed that every pronounced rais- 

 ing of the head or trunk brought about an interruption 



