RECORDS OF THE
SEPTEMBER-COMMISSION 255

IV. THE REPORT OF DECEMBER 9th, 1904 261

TABLE OF REFERENCES 267

INTRODUCTION

[BY C. STUMPF]

A horse that solves correctly problems in multiplication and division by
means of tapping. Persons of unimpeachable honor, who in the master's
absence have received responses, and assure us that in the process they
have not made even the slightest sign. Thousands of spectators,
horse-fanciers, trick-trainers of first rank, and not one of them during
the course of many months' observations are able to discover any kind of
regular signal.

That was the riddle. And its solution was found in the unintentional
minimal movements of the horse's questioner.

Simple though it may seem, the history of the solution is nevertheless
quite complex, and one of the important incidents in it is the
appearance of the zooelogist and African traveler, Schillings, upon the
scene, and then there is the report of the so-called Hans-Commission of
September 12, 1904. And finally there is the scientific investigation,
the results of which were published in my report of December 9, 1904.

After a cursory inspection during the month of February, I again called
upon Mr. von Osten in July, and asked him to explain to Professor
Schumann and me just what method he had used in instructing the horse.
We hoped in this way to gain a clue to the mechanism of Hans's feats.
The most essential parts of the information thus gleaned are summarized
in Supplement I. Mr. Schillings came into the courtyard for the first
time about the middle of July. He came as skeptical as everyone else.
But after he, himself, had received correct responses, he too became
convinced, and devoted much of his time to exhibiting the horse, and
daily brought new guests. To be perfectly frank, at the time this seemed
to us a disturbing factor in the investigation, but now we see that his
intervention was a link in the chain of events which finally led to an
explanation. For it was through him that the fact was established beyond
cavil, that the horse was able to respond to strangers in the master's
absence. Heretofore, this had been noted only in isolated cases. Since
it could not be assumed that a well-known investigator should take it
upon himself to mislead the public by intentionally giving signs, the
case necessarily from that