In this report of the results of our experiments, the reader must bear in mind that it was impossible to adhere to that order and distribution of tests which we are wont to require in the case of psychophysical experiments conducted under regular laboratory conditions. All sorts of difficulties had to be overcome: unfavorable weather, the crowds of curious ones, certain peculiarities of the horse—such as shying whenever the wind rippled the canvas of the tent—and last but not least, the idiosyncrasies of Mr. von Osten who repeatedly attempted to interrupt the progress of the experiments.
Since it was evident that different kinds of processes were involved in solving the problems and since the solutions would be indicated by tapping, or by movements of the head, or by walking over to the object to be designated, the results of these three sets of experiments have been grouped under three corresponding heads.
I. Problems solved by tapping
The following tests were made in which the method was such that when the problem was presented to the horse, the correct solution was known to none of those present, least of all to the questioner. This method we shall designate in the following report as "procedure without knowledge" whereas we shall call the method in which the answer was known to the questioner, "procedure with knowledge".
In order to discover if the horse could read numbers, a series of cards on which numerals were blazoned, were exposed to the horse's view in such a way that none of those present was able to see them, and the horse was asked to tap the numbers as they were shown. This experiment was repeated at different times and in all there were 49 tests in which procedure was without knowledge, and 42 in which procedure was with knowledge. In the case of the former there were 8% correct responses, whereas in the case of the latter 98% of the answers were right. As an example of the course which the series tended to take, we insert the following, in which Mr. von Osten himself acted as questioner.
| Method. | No. exposed. | No. tapped. | ||||||
|---|---|---|---|---|---|---|---|---|
| Without | knowledge | 8 | 14 | |||||
| With | " | 8 | 8 | |||||
| Without | " | 4 | 8 | |||||
| With | " | 4 | 4 | |||||
| Without | " | 7 | 9 | |||||
| With | " | 7 | 7 | |||||
| Without | " | 10 | 17 | |||||
| With | " | 10 | 10 | |||||
| Without | " | 3 | 9 | |||||
| With | " | 3 | 3 | etc. | ||||
Whenever the questioner knew the solution, nearly all of the horse's answers were correct; but when the answers were unknown to the questioner, the horse's responses were, with only a few exceptions, quite unsuccessful. Since the few exceptional cases must be regarded as fortuitous, the conclusion is warranted that the horse was unable to read numerals without assistance.
In order to discover whether the horse could read words such as "Hans" or "Stall" or the names of colors, they were written upon placards and hung up in a row before the horse in such a way that the questioner could see the individual word but could not immediately recognize the particular place that each one occupied in the series. The horse was then asked: "Upon which placard is the word
'Hans'?", "On which is the word 'Stall'?", etc. In order to make sure, he was required to repeat each answer.
Then the experimenter would determine for himself the place of the word in the series and would ask the question again. Fourteen such tests, in which the procedure was with knowledge on the part of the questioner, were interspersed with twelve in which the procedure was without such knowledge. With the latter there were no correct responses, whereas in the cases of procedure with knowledge 100% of the answers were correct. Evidently the horse could not read words.