52 THE HORSE OF MR. VON OSTEN 



the head-jerk, then the watches would have to show a later 

 time for the back-step than for the head-jerk. 



Measurements of this kind were taken for Mr. von 

 Osten, Mr. Schillings and myself. In the case of the 

 first two it was taken without any knowledge on their 

 part. They did not even know that they were being ob- 

 served, having been told that the measurements were for 

 the sake of determining the horse's rate. In my case, to 

 be sure, the time could not be taken without my knowl- 

 edge. I succeeded, however, in eliminating the effect of 

 this knowledge on my part. (Cf. pages 88 and 145.) 

 Since the results obtained in the case of Mr. Schillings 

 quite agree with those obtained in my case, it is evident 

 they may be considered as being of equal value. 



With regard to the number of tests the following table 

 may be referred to. The first vertical column gives the 



to a visual cue. (Hans's tapping was almost quite inaudible). Both 

 stop-watches were carefully regulated. In order to eliminate also the 

 constant error which might possibly arise as a result of some difference 

 in the functioning of their pressure-mechanism, the two watches were 

 always exchanged in the different series of tests, by the observer of the 

 man and the observer of the horse. The two time-measurements ob 

 tained by the two observers contained, of course, the reaction-times of 

 the observers themselves. In order to equalize the constant error which 

 thereby arose, it was arranged that each observer should react alternately 

 now to the man, now to the horse. In order to be perfectly safe, the 

 reaction-times of those concerned, (von Hornbostel, Pfungst, Schumann 

 and Stumpf), were later determined in the laboratory by means of the 

 carefully regulated Hipp chronoscope. Separate determinations were 

 made of the reactions to the head-jerk and to an imitation of the horse's 

 back-step. Then the time which one observer took to react upon a 

 head-jerk, was compared vrith the reaction-times of the other observers 

 to the back-step. Since the greatest difference which was found in this 

 comparison, did not exceed one-tenth second, the results obtained in the 

 courtyard required no correction. 



