the right. Whenever he began with the left, Mr. von
Osten would immediately interrupt him, and he was allowed to add only a
final tap with his left foot. Thus, this additional tap which was
sometimes made with the left foot was but the vestige of an earlier
rudimentary habit. The signal for it was the stooping posture in which
the master remained after the head-jerk had been made. Whenever Mr. von
Osten had given Hans a small number to tap, he would bend forward only a
little. But when he expected a larger number he would bend forward
somewhat more, owing to the desire to observe the tapping more
carefully. From the slight inclination of the master's body the horse
would get the cue that he was expected to tap for a short time only, by
the greater degree of inclination he would know that he was to tap for a
longer period. In the second case he tapped rapidly and did not raise
his foot as high from the ground--evincing a regard for the saving of
energy, which may well be attributed to a horse. And thus arose the
connection between the degree of inclination of the instructor's body
and the horse's rate of tapping.

So, now that the ability to count and solve problems had become
fixed--as the old gentleman thought--he began to instruct the horse in
other branches. Since everything had been translated into terms which
were to be expressed by means of tapping with the foot, and thus really
put into terms of number--which was perhaps natural for an old teacher
of mathematics--the same mechanism was involved in these accomplishments
as in those of counting, etc. Mr. von Osten saw the animal's
intelligence steadily increase, without having the slightest notion that
between his words and the responsive movements of the horse, there were
interpolated his own unconscious movements--and that thus instead of the
much desired intellectual feats on the part of the horse, there was
merely a motor reaction to a purely sensory stimulus. It has been a
common custom of man to posit some extraneous cause for movements
resulting from certain involuntary motions of his own, of which he is
not aware, (witness the divining-rod).[AM] And furthermore, when these
results appear to be rational, the tendency is to seek their cause in
some extraneous intelligence, not his own. Just as the spiritualists
ascribe the "messages" which are revealed to them through table-rapping,
to certain rational spirits, so Mr. von Osten credited the intelligence
of th