Figure 9 (von Allesch) is expressive of great, but--according to the subject's introspection--not economical concentration. Respiration, which before and after the test was quite regular, during the test itself shows a pause. (The tiny waves are due to the heart-beat.) The subject had thought of 5, and this number is accompanied by a decided head-jerk. But we note that even before the final jerk a number of less pronounced jerks occur--the result of poorly regulated psychic tension. [Illustration: FIG. 8.] [Illustration: FIG. 9.] Figure 10 (Schillings) depicts a very high degree of uneconomical concentration. There was sudden concentration at the beginning of the test, and a steady increase throughout its course. Accordingly Mr. Schillings bent forward at the start, and inclined still farther forward at the second--and just before the third--tap. But at 3 there is a sudden upward jerk. The number thought of had been 4, tension therefore had exploded, as it were, too soon. [Illustration: FIG. 10.] Figure 11 (again of Schillings) gives indications, on the other hand, of a medium and economic concentration of attention, which is more normal in character. The number thought of was 4. [Illustration: FIG. 11.] Figure 12 (Schillings again) is indicative of a low degree of psychic tension. With the very first tap the head begins to rise and continues to do so throughout the test. A true final jerk does not occur, we note rather in all three curves registering the head movements, slight time-marking movements, especially in the second curve. In the third curve they are at first minute, but increase steadily in size until the fourth tap, after which they suddenly disappear. The subject had, as a matter of fact, thought of the number 4, but it is hardly probable that Hans would have reacted properly upon these stimuli. [Illustration: FIG. 12.] Mr. Schillings had thought of the same number in all three tests given in figures 10, 11 and 12. The probabilities are that if he had been working with the horse at the time, in the first case Hans would have reacted with three taps with the right foot and a final tap with the left, as a result of the questioner's bending forward again after the premature head-jerk at 3. In the second instance the horse would probably have given four taps with the right foot, and in the third, the chances are that he would have continued to tap beyond the 4. These curves give, on the whole, a fair idea of the intensity and of the course of attention of the various subjects.