ntly Hans was unable to spell without
assistance of some sort from the questioner.

The horse's reputed aptitude in computation was tested in the following
way. Mr. von Osten whispered a number in the horse's ear so that none of
the persons present could hear. Thereupon I did likewise. Hans was asked
to add the two. Since each of the experimenters knew only his own
number, the sum, if known to anyone, could be known to Hans alone. Every
such test was immediately repeated with the result known to the
experimenters. In 31 tests in which the method was procedure without
knowledge, 3 of the horse's answers were correct, whereas in the 31
tests in which the method was procedure with knowledge, 29 of his
responses were correct. Since the three correct answers in the cases in
which procedure was without knowledge evidently were accidental, the
results of this series of experiments show that Hans was unable to solve
arithmetical problems.

For the purpose of discovering whether the horse could at least count,
the Russian kindergarten device, which Mr. von Osten had used in
training, was utilized. The machine was placed before the horse, but the
experimenter turned his back upon it. Before each test, a number of
balls were pushed to one side and Hans's problem was to indicate the
number thus separated. Each test was repeated with procedure with
knowledge. Of eight such experiments Hans responded successfully every
time procedure was with knowledge but failed every time procedure was
without knowledge. Thus 7 balls were at one time designated as 9 and
later as 14, while 6 were at first designated as 12, and later as 10.
Since all these errors could not be accounted for on the ground of
miscounts on the part of the horse, it was evident that Hans is quite
unable to count.

The memory-test was conducted in the following manner. In the absence of
the questioner a number or the name of some day of the week was spoken
to the horse. The experimenter would then return and question him. Of 10
responses 2 were correct, 8 incorrect. Among the correct answers were
the number 3, a number which, as we shall see, Hans was prone to give
under all sorts of conditions, and which therefore meant very little
when given as a correct response. The number 2, on the other hand, was
consecutively indicated by 7, 9, 5, and 3, 8 was given as 5, 6, 4, and
6, consecutively; and finally Wednesday was indicated as the fourteenth
day of the week. After this