152 THE HORSE OF MR. VON OSTEN 



voke the aid of perceptual objects to bring his attention 

 to the proper height of concentration. 



The reader will see that thus far I have supposed the 

 horse to be a never-failing mechanism and that I have 

 placed all errors to the account of the questioner. The 

 horse never failed to note the signal for. stopping and 

 therefore never was the immediate cause of an error. It 

 is not to be denied that now and then he would cease 

 tapping spontaneously and in this way would become 

 the cause of an error. We have no data on this point, but 

 undoubtedly the horse's share in the total number of 

 errors was very slight. 



(&.) Another source of error was faulty computation 

 on the part of the questioner. The questioner made the 

 signal for stopping when the expected number of taps 

 had been reached. The horse faithfully mirrored the 

 miscalculation of the questioner. I have knowledge of 

 only one such case. The journals report that once Mr. 

 von Osten, when someone called to his attention that Hans 

 had indicated the wrong day of the week, replied : " Yes, 

 you are right, it was not Thursday, but Friday," where- 

 upon Hans being asked again, promptly responded cor- 

 rectly. This appeared to the reporter in question as proof 

 of the subjective influence of Mr. von Osten upon the 

 horse. 



f — (c.) When errors in calculation and failures in proper 

 concentration combine, i. e. when the questioner makes a 

 mistake in calculation because he is excited or inatten- 

 tive and for the same reason does not make the move- 

 ment, which is the signal for stopping, in accordance 

 with the number which he deems to be the correct an- 

 swer, then the result is usually wrong, but it may be cor- 

 rect in the few cases in which the two errors exactly 

 compensate each other. Nothing has been so effective 



