sible, still are improbable, I believe that our Hans,
Huggins's dog, and the one belonging to Mr. Kretschmer, differ from one
another only in this, that the first taps, the second barks, and the
third presses a bell-button.

And finally I have access to a letter from the Rhine Province in which
there is a brief account of a dog that would promptly obey any command
that was given without a sound and supposedly without the accompaniment
of the slightest kind of gesture. It is specially mentioned that the
animal steadily watched its master during these tests. The perception of
the slightest involuntary expressive movements is in all probability the
secret in this case also. Here, too, suggestion has been invoked by way
of explanation, but there was not the slightest attempt made to find for
it a more specific foundation, and we cannot suppress an objection based
on the matter of principle. It is incumbent upon anyone who uses a term
so ambiguous, to define what content he desires to have put into it. If
he does not do this, he is giving us, instead of a concept, a bare word,
instead of bread, a stone.

While we must reject the explanation based on suggestion,[AC] we
believe, on the other hand, that we have here again, evidence of the
presence of visual signs, given unwittingly and involuntarily, just as I
am sure that they were involved in the two preceding cases, and
similarly in the case of the Huggins dog. Since the effective signs were
discoverable in none of these canine predecessors of Hans, an
investigation would be desirable, based upon the insight gained as a
result of these experiments upon Mr. von Osten's horse. Unfortunately
this is impossible, since the dogs in question are dead. But others like
them undoubtedly exist in many places. We might mention that when Hans
first came under the limelight of public attention, there was also
frequent reference to the Huggins dog, but he soon dropped out of the
discussion again.[63] And this for two reasons. The dog never took his
gaze from his master and appeared to be entirely dependent upon him in
his reactions. Hans, on the other hand, seemed to give evidence of a
high degree of independence and never appeared to look at the
questioner. But we know now that, though he was never dependent upon the
will of his master, he, too, abjectly hung upon the man's involuntary
movements and never for a moment lost him from view. But since the horse
is able to observe with one ey