With regard to the number of tests the following table
may be referred to. The first vertical column gives the


toa 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 upona
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.
