. But it was only in the
first case that he would receive a reward. Thus, unknown to the
instructor, an association became established between the sight of the
upward jerk of the instructor and the act of ceasing to tap. To be sure,
the animal would receive sundry visual impressions from the wooden pins
set up before him and the auditory stimulations of the spoken number
names, on the basis of which, the concepts were to be formed in his
mind. But in this chaos of visual impressions (at times there were two
wooden pins, then three, then four, sometimes there were the pins, at
others, the balls of the counting-machine)--and in the babel of
word-sounds--which evidently meant nothing but noise to him--amidst all
this there was but one constant element: the final movement of the
instructor's body. The moment the horse reacted to this, he would
receive the tidbit at the hands of his overjoyed master, and thus he
became more and more accustomed to attend to this jerk, even after it
had gradually decreased in scope. And the reason again, why this jerk
tended to become less pronounced was that the tests were gradually
becoming more and more successful. For, corresponding to the degree in
which the horse began to react properly, the instructor's tenseness and
excitement tended to decrease, and with this decrease of the emotional
element in the man's consciousness, the accompanying non-voluntary,
expressive movement gradually became less pronounced until it attained
that extraordinary refinement which it possesses to-day. We noticed
also, that whenever the horse, for any reason, had to be trained anew,
Mr. von Osten's movements would, on the whole, become somewhat more
gross, as for instance after the tests with the blinders. There is not a
shadow of a doubt that this increase in the movement's extent was
entirely unintentional, since the horse could not see his master at all
on account of the blinders which had been attached to the trappings.

[Footnote AL: This natural and close connection between the process
of attention and the movement toward the object attended to is
clearly expressed in our English and French terms, derived from the
Latin "tendere ad--," to reach toward--.]

In the same way it is possible to explain the details. Mr. von Osten
himself said that at first Hans had tapped at times with his left foot,
at times with his right, just as he pleased. But later his master taught
him to tap only with