er might
assume with reference to the horse, the following may be noted: The
normal position was to the right of the horse. If the experimenter stood
immediately in front of Hans, the latter's reaction would be just as
accurate, though he would always turn his head and make desperate
efforts to see the questioner, even though he was held in short by the
reins. When a position immediately behind the horse was taken--a
somewhat dangerous proceeding, since Hans would at once begin to
kick--no response could be obtained until he succeeded in turning far
enough around to get the questioner within view. If he was restrained
from turning completely around, he would at least turn his head,--and
always to the right. One might even turn his back upon Hans during the
tests, for the signal for stopping was not obtained from the face of the
questioner, but from a movement of the head. The following incident will
show to what extent the horse had become accustomed to seeing the
questioner in a certain definite position. For a long time I had been
in the habit--without exception--of standing close to the horse's
shoulder. Mr. von Osten, on the other hand, would stand farther back.
When, on a certain day, I assumed the latter position, the horse would
not suffer it, but would move backward until he had his accustomed view
of me.

Finally we sought to discover by what movements the horse could be made
to cease tapping. We discovered that upward movements served as signals
for stopping. The raising of the head was the most effective, though the
raising of the eyebrows, or the dilation of the nostrils--as in a
sneer--seemed also to be efficacious. However, it was impossible for me
to discover whether or not these latter movements were accompanied by
some slight, involuntary upward movement of the head. The upward
movement of the head was ineffective only when it did not occur as a
jerk, but was executed in a circuitous form,--first upward and then back
again. Such a movement was occasionally observed in the case of Mr. von
Osten. The elevation of the arms or of the elbow nearest the horse, or
the elevation of the entire body was also effective. Even if a placard,
with which the experimenter tried to cover his face, were raised at a
given moment, the horse would make the back-step. On the other hand,
head movements to the right and to the left or forward and back, in
fine, all horizontal movements, remained ineffective. We also found that