Hans, however, was also a faithful mirror of all the errors of the questioner. Aside from mistakes due to occasional interruptions on the part of visitors, these errors had two sources: faulty computation and inadequate concentration--i. e., aside from arithmetical errors on the part of the questioner, were his premature or belated movements. Since both of these factors might be operative, the following three possibilities arise. (_a_) The questioner computes correctly but does not move at the proper moment. Nearly all the errors which had been accredited to the horse, were of this kind. A part of these errors had the appearance of being significant, that is, they might be interpreted as a misapprehension of the question. If, for instance, instead of a sum only one of the quantities was given, or, if instead of a product only one of the factors was given, it might be interpreted that the horse simply wished to repeat the problem. Thus, Mr. von Osten in response to the question: "How much is 3 times 5?", twice in succession received the answer, "3", and upon my question, "How much is 3 plus 4?" he answered, "3", and to "How much is 2 times 6?" he tapped 6, and to "What is one-fourth of 36?" 4. In part (certainly in the second and third example cited) an individual quantity or factor had been emphasized in the consciousness of the questioner (cf. page 105) and in part the reactions were due to chance. Thus, when Mr. Hahn asked the question: "What is one-half of 10?", he received the following responses: 2 and 10, and then 17 and 3. To this class belong also, the tests made by the Commission of September and reported in Supplement III. (See page 255).