EXPERIMENTS AND OBSERVATIONS 63 



time I had been in the habit — without exception — of 

 standing close to the horse's shoulder. Mr. von Osten, 

 on the other hand, would stand farther back. When, on a 

 certain day, I assumed the latter position, the horse would 

 not suffer it, but would move backward until he had his 

 accustomed view of me. 



Finally we sought to discover by what movements the 

 horse could be made to cease tapping. We discovered 

 that upward movements served as signals for stopping. 

 The raising of the head was the most eilective, though 

 the raising of the eyebrows, or the dilation of the nostrils 

 — as in a sneer — seemed also to be efficacious. However, 

 it was impossible for me to discover whether or not these 

 latter movements were accompanied by some slight, 

 involuntary upward movement of the head. The upward 

 movement of the head was ineffective only when it did not 

 occur as a jerk, but was executed in a circuitous form, — 

 first upward and then back again. Such a movement was 

 occasionally observed in the case of Mr. von Osten. The 

 elevation of the arms or of the elbow nearest the horse, or 

 the elevation of the entire body was also effective. Even 

 if a placard, with which the experimenter tried to cover 

 his face, were raised at a given moment, the horse would 

 make the back-step. On the other hand, head movements 

 to the right and to the left or forward and back, in fine, 

 all horizontal movements, remained ineffective. We also 

 found that all hand movements, including the " wonder- 

 fully effective thrust of the hand into the pocket filled with 

 carrots ", brought no response. I might also change my 

 position and walk forward and then backward some dis- 

 tance behind the horse, but the back-step would only occur 

 in response to the characteristic stimulus. After what 

 has been said it is easy to understand how vain were Mr. 



