THE AUTHOR'S INTROSPECTIONS 95 



voluntary control of the movements involved. Hans 

 thus solved for me the same ten problems first with the 

 back-step, then with the extra final tap. 



Finally we will indicate the one true inner cause of the 

 difficulty in getting the number i as a response. It is not 

 easy to relax attention immediately after having just 

 begun to concentrate. Relaxation, therefore, often oc- 

 curs with a certain retardation, and the result is a belated 

 jerk of the head. 



Briefly, I would also mention a few of the more inter- 

 esting introspective observations which were made in 

 situations in which the horse responded with movements 

 of the head for answers such as " yes " and " no ", " up " 

 and " down ", etc. From the very beginning I put ques- 

 tions to Hans which would have to be answered by a 

 shake of the head. It often happened that instead of indi- 

 cating " o ", Hans would begin tapping some number. 

 But the wonder of it was that, in many cases, he re- 

 sponded properly. I knew only that I inwardly pro- 

 nounced the word "null" (zero), and that I looked ex- 

 pectantly at the horse's head. In the case of questions to 

 which I expected the answer " yes " or " no ", I imagined 

 myself enunciating the answer, i. e., I used motor im- 

 agery. The tests failed, the moment I employed only 

 visual or auditory imagery, whereas, motor imagery was 

 always effective in calling forth correct reactions.* When 



* Thus it is possible to think of the word " no " in three differ- 

 ent ways. I may get a visual image of the written or printed word, 

 or the auditory image of the word as spoken by another person, or 

 finally I might think of it in terms of images of the sensations of move- 

 ment which would arise if I myself were to enunciate or write the word. 

 And so, in like manner, I could think of any other word in terms of 

 either visual or auditory or motor imagery. In all probability the 



