TABLE V
| Obs. | H first | H middle | H last | |||
| A | Threshold Mean After Letter | .010 (sec.) | After Letter | .021 (sec.) | After Letter | .025 (sec.) |
| Range | .072 (sec.) | .085 (sec.) | .093 (sec.) | |||
| G | Threshold Mean Before Letter | .007 (sec.) | On Letter | Before Letter | .007 (sec.) | |
| Range | .124 (sec.) | .083 (sec.) | .151 (sec.) | |||
| R | Threshold Mean After Letter | .032 (sec.) | After Letter | .016 (sec.) | After Letter | .042 (sec.) |
| Range | .464 (sec.) | .398 (sec.) | .369 (sec.) | |||
| Sh | Threshold Mean After Letter | .025 (sec.) | After Letter | .015 (sec.) | After Letter | .030 (sec.) |
| Range | .176 (sec.) | .176 (sec.) | .166 (sec.) | |||
| St | Threshold Mean After Letter | .050 (sec.) | After Letter | .062 (sec.) | After Letter | .078 (sec.) |
| Range | .140 (sec.) | .108 (sec.) | .108 (sec.) |
Under these conditions, whatever the effect of the visual series, if it has any effect, opposite tendencies in direction of displacement ought to be shown in the "H last" from those in the "H first," results, as each is contrasted with "H middle." Contrasted in this way, these results, for A and St, show a relative approach of the mean to zero for "H first," and a relative departure from zero for "H last," or a decrease of a negative displacement for "H first" and an increase of the same for "H last." In other words, the series draws the displacement of the click toward itself. A negative displacement is increased by a series coming before the visual stimulus in question, and decreased by such a series coming after. For R and Sh, the negative displacement is increased in both H first and H last as compared with H middle, but relatively the most for H last in both observers. For G there is the same positive displacement introduced by both H first and H last, but it is less than in any of the other cases. The drift of the evidence here, then, is that the visual series draws the displacement in its own direction. Each observer who has a negative displacement (Threshold mean after) with "H middle" increases this when the series all comes before (H last) and two decrease it when the series comes after (H first).
THE EFFECT OF RHYTHM (Repetition of Auditory and of Both Stimuli)
It is very evident to any one who has worked at all in the complication experiment, that rhythm plays an important part in the displacement. Witness also the astronomers' experience cited above, St's waiting for the rhythm to establish itself, and my own readjustment to the new conditions when a new combination of intervals was given in the experiment with varying auditory intervals. In order to show the part played by rhythm, I tested each one of five observers on several different days, to fix for each of them both the "click first" and the "click last" thresholds, as above, under each of the following conditions: (1) one visual (single letter) and one auditory stimulus (one pair), (2) one visual (single letter) and many auditory stimuli, and (3) many visual (single letter repeated) and many auditory stimuli (many pairs). For visual fixation, the observer had a very dim light at the end of the observation-tube. The visual stimulus was a flash of red in the place thus fixated. It had a total duration of less than .005 sec. The surface exposed subtended a vertical visual angle of about seven tenths of a degree. In the case of one visual and many auditory stimuli, the visual stimulus was given when the observer had heard the recurring auditory stimuli several times and had himself given the "ready" signal. The results follow in Table VI.