within the power of
the experimenter to have the tapping executed entirely with the right
foot or with the final extra tap of the left foot. Hitherto the view had
been current that this lay solely within the pleasure of the horse.

If the questioner still inclined forward, still remained in the bent
posture after Hans had given the final tap with his left foot, the horse
would immediately begin to tap once more with his right foot, which had,
in the meantime, become ready for further action. If the head jerk was
then made, Hans would bring his right foot back, give the extra tap with
his left foot, then resume tapping with the right and thus continue
until the questioner once more resumed the erect posture. Thus the horse
on one occasion when I wished him to tap 100, gave--contrary to my
desire--the following response; 39 with the right foot, 1 with the left,
24 with the right, 1 with the left, 35 with the right, and 1 with the
left. Later it became possible for me to cause him to tap 1 right, 1
left, 1 right, 1 left, etc. I could even get him to tap exclusively with
the left foot by standing at his left rather than at his right as had
been customary with his questioners. These taps with the left foot were
executed in a far less elegant fashion than those with the right foot,
and with a great waste of energy. Hans had become a right-handed
individual--as it were--as a result of long habit.

With regard to the distance at which the experimenter directed the
horse, the following may be said: The usual distance was one-quarter to
one-half meter. This holds for all tests hitherto described. Seventy
tests which were made for the purpose of discovering the influence of
change in distance showed that the reaction of the horse upon the
customary signal of the head-jerk was accurate up to a distance of three
and one-half meters. At a distance of three and one-half to four meters
there suddenly occurred a fall of 60-70% in the number of correct
responses. At a distance of four to four and one-half meters only
one-third of the responses were correct, and at a distance beyond four
and one-half meters there were no correct responses. The greater number
of these tests were made in our presence by Mr. von Osten, who was under
the impression that we were testing the accuracy of the horse's hearing,
whereas we were really testing the accuracy of his perception of
movements.

With regard to the different positions which the experiment