While the errors thus far discussed appeared sporadically in long series of correct responses, there still might be observed at times a massing of errors, usually at the beginning of a day of experimentation or at the beginning of a new series. We were regularly told that Hans always had to have time to adjust himself to new circumstances. The records often showed comments such as these: "After a number of practice tests the horse appears particularly well disposed", or "Hans, at first inattentive, does not respond. Suddenly he gets the hang of things". Different questioners who worked with the horse required different lengths of time to obtain proper responses. Some needed a quarter of an hour, others scarcely half a minute. I, myself, found that in the degree in which I learned to control my attention, in that degree did this phenomenon tend to disappear, but would reappear the moment I became indisposed. From this we see that, instead of attributing all sorts of mental characteristics, such as stubbornness, etc., to the horse, we should lay them to the account of the questioner. As a matter of fact we find that this "getting into the sweep of things", i. e. the overcoming of psycho-physical inertia, has long been known in the case of man and has been experimentally determined and called "Anregung" (excitation) by the psychiatrist, Kraepelin,[22] and his pupil, Amberg.[23] A massing of errors toward the end of a long series occurred only when the questioner was fatigued. There was nothing which had to be interpreted as fatigue or as indisposition on the part of the horse, (except in the few cases of very large numbers, cf. page 67). To be sure, Mr. von Osten always offered these two excuses. That they were without warrant is shown by the fact that Hans, after appearing indisposed or fatigued while working with one questioner, would nevertheless react promptly and correctly a moment later for some other experimenter, and furthermore, when working with me, the number of his correct responses would rise or fall with my own mental disposition.