Note J — Chapter II · EXPERIMENTS AND OBSERVATIONS

For the benefit of those who are familiar with reaction-time experiments of this kind, I would state the following: The reaction to the head-jerk, on account of the minuteness of the latter, was sensory throughout, and therefore all precipitate reactions are entirely wanting. The reaction to the back-step was, like the preceding one, a reaction 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 obtained 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 with 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.