From this we see how hard it was at first to get the number 1 and that failure was as frequent as success, and how much easier it was on the other hand to get the numbers 2 and 3 (and which, therefore, do not show any great improvement in the second half of the tests). Beyond the 3 the percentage of correct responses decreased and the number 7 stood at the same level as the number 1. In the second half of the tests, all these differences disappeared and errors were infrequent and seldom exceeded +1 or -1. These results of practice are not to be accredited to the horse, but to the experimenter, who was at first quite unskilled. This difference in results does not appear in the case of Mr. von Osten, for his initial practice had been had many years previous. The values obtained in his case were very constant throughout our experimentation and generally showed something like 90% of correct responses. To be sure, in his case also, the number 1 was somewhat unfavorable, (79% were correct responses). But the percentages obtained in his case showed no improvement whatever throughout our experimentation. We need scarcely add that with the voluntary control of the giving of the signs, in the case at least of such small numbers as are here discussed, no errors, whatever, occurred. We have discussed the influence of the experimenter, i. e., the one who asked the horse to tap; now let us consider the influence of others present upon the horse. As a general rule, other persons had no effect upon the horse's responses. This appears from the failure of nearly all tests in which all of those present--with the exception of the questioner himself--knew the number which the horse was to tap. Even when the others concentrated their whole attention upon the number, it profited little as a close analysis of the 136 cases, which belong under this head in our records, go to prove. Thus, in the presence of a group of twenty interested persons--during the absence of Mr. von Osten--twenty-one problems were given to the horse, the solutions of which were known to everyone but myself, the questioner. Result: only two correct responses. Only when there was among the spectators someone to whom the horse was accustomed to respond or one from whom he regularly received his food, would such an influence be effective.[L] But such cases were few. The most important were the following: I at one time whispered a number to Hans (on the occasion of the tests mentioned on page 37), and Mr. von Osten asked for it the moment I stepped aside. Hans answered incorrectly even though I stood close beside Mr. von Osten; I did not, however, think intently of the number. As soon as I concentrated my attention upon the number he promptly responded correctly. Further cases are those mentioned on page 38, in which the keeper of the horse unintentionally aided in giving four dates which were unknown to all others present, including the questioner. This single instance shows the necessity of