chillings it was the
least pronounced, in comparison with his very strong "jerk". Yet in both
cases Hans responded with absolute certainty.

It is now readily conceivable how it was possible to make the horse
respond to all sorts of foolish questions, both by involuntary signs--i.
e., expressions following upon the bare imaging of the response
expected,--as well as by means of controlled signs. One could thus
obtain consecutively the answers "yes" and "no" to the same question. Or
one might ask: "Hans, where is your head?", and Hans would bend to the
earth. "And where are your legs?" He would look at the skies. Etc.

Let us examine for a moment the directives which the horse required for
the various positions. If one called him, while he was running about the
courtyard, he paid no attention whatever, but if one beckoned to him, he
came immediately. A raising of the hand brought him to a standstill. If
one now stepped forward or pointed one's hand in that direction, he
would step forward, or _vice versa_, he would step backward. By means of
minimal movements of the head, of the arm nearest the horse, or of the
whole body, Hans could be induced to assume the position one desired,
without touching him or speaking a word. I noticed this quite early in
the course of the investigation. Once, when intending to ask the horse
to step backward to the right, I inadvertently said "Step backward to
the left!", whereupon he stepped backward to the right. In spite of my
verbal error, I had involuntarily given him the proper directives.

Finally we may note that Mr. von Osten had occasionally asked the horse
to jump or to rear. The command in this case was: "Jump", or the
question was: "What do the horses do in the circus?". Since these tests
were just as effective when the command was given silently, it was an
indication that these, too, depended upon visual stimuli. What was
necessary to cause the horse to step backward and then jump forward was
to step backward oneself, or make a slight movement of the hand in that
direction. If one wished to make him rear, it might be effected by
throwing the arm or head slightly upward.

_III. Problems which Hans solved by approaching the objects to be
designated._

The method pursued in these tests was the following: From five to eight
pieces of colored cloth 1/2 x 1/4 meters in size were arranged in
changing series upon the ground, the interval between them being equal
to the width of one