d be necessary to explain how it was
possible for him to train the horse to heed the cues.--In the course of
time, the instructor may have noticed that whenever he moved during the
course of a test the horse invariably failed. But he may have regarded
this merely as an incidental distraction and afterward was careful to
remain quiet. As soon as he increased the number of cloths upon the
floor, it was no longer possible for him to give the horse such accurate
directive signs, and the number of errors consequently increased.
Ascribing them to the inattentiveness of his pupil, he sought to
encourage him by such calls as "look out", "look there", "see there",
believing that, thus, he was directing the horse's attention to the
desired color. Without understanding the meaning of the calls, Hans
learned, however, to keep moving just as long as the calling continued,
for if he did this he was regularly rewarded. An association was
established between the call and the impulse to move on. And with these
two associations established, Hans gave the impression of having grasped
the meaning of the color terms.

The origin of the proper movements in response to the terms "up" and
"down" may be explained by the fact that the movements themselves were
practised in a purely external fashion. Thus, whenever the word "left"
was pronounced, the horse's head was pulled to the left by means of the
bridle or the reward was held off to that side. Later, Mr. von Osten,
who looked expectantly at the horse's head, whenever he pronounced the
word would unconsciously move his own head in the direction in which he
desired the horse to turn. This is quite in accord with the words of
Darwin to the effect that whenever we wish an object to move in a
certain direction it is well-nigh impossible for us to inhibit an
unconscious, involuntary movement in that direction. Proof for this may
be found on all sides, in daily experience.[97] Imagine, for instance,
the strain sensations of the bowler or billiard player as he follows the
moving ball. It is impossible to decide whether Mr. von Osten,
consciously continued to image the head movements which he expected the
horse to make or whether these anticipatory images later remained below
the threshold as was always the case with Mr. Schillings and myself (see
page 100). But this question is of little significance, for even
assuming that he always thought of the movement he expected on the part
of the horse, this