A.'s cases were these. The 'wraith' of a small box whose image was out at the right, appeared above the other image off at the left and it was turned with a corner to the front. Again, at the central position each image was duplicated, the true pair being of full size, bright and distinct, the false pair small, dim and on a more distant plane, i.e., behind the others. One of the extra images persisted against all effort to banish it, for fifty-five seconds. Again, when twelve inches apart each image was similarly duplicated. In the fourth instance the images were at the center of the field. In the fifth, the right image, eight inches from the center, was duplicated, the extra image being still farther away and above. This second image was very dark, dim and vague in outline, and came and went slowly. The right image of C., when seven feet from the center, had a dim double above it. F. had moved the right-hand image (a violet disc) close to the left when a blue disc also appeared above it. Though repeating the word 'violet' he had imaged the violet disc as blue. K. was holding the two images a foot and a half apart when an extra pair appeared at the center. Both pairs persisted for sixty seconds and then the outer pair vanished, and the inner, the false pair, grew brighter.
As was said in the case of a single image, so with double images, the motion could be traced and often was traced when the movements were away from the original positions, but on the return to the original positions the images were not usually seen in transitu. For ten of the subjects, the image moved downward uniformly on an arc whose center was at the eye; and often the right and left movements were likewise on an arc. With E. the ends of the arc for motion right and left were higher also. H., I. and J. reported that all the movements were in the same plane. The upward movement was always to a less distance and the downward movement to a greater distance than the horizontal movements.
In most cases the images were the size of the percepts, in a number of cases smaller, and in a few cases larger. This was determined by comparison between the image and the percept immediately on opening the eyes and seeing the object at the end of the five minutes occupied by the experiment. A similar mode of comparison showed that, in about half of the experiments, the images were at the end of five minutes approximately equal to the percept in clearness and distinctness of outline. A comparison of these results with those obtained in a series of experiments involving passive observation of the image seems to indicate that active manipulation of the image tends to maintain the qualitative fidelity of the image when at its original position. During the progress of the experiments the reports were almost unanimous and constant that at its original position the image was vivid and distinct, but lost in both respects when away from that position, the loss being greater the greater the distance to which it was moved. Frequently there was fluctuation,—a loss of vividness and then a restoration,—which A. frequently found to be rhythmical, while in general it was evident that an increase of effort or of attention was successful in restoring lost vividness and distinctness.
D., after three minutes, read the time in the image of a watch. In superposing green on yellow, in two instances, the yellow shone through, making a mixed color, and again, in moving a green disc and a yellow disc, the green became suffused with yellow, so that the two discs were one yellow and the other greenish-yellow. For C., similarity in the two objects presented tended to make both images less vivid and distinct and to render more difficult their retention and manipulation. When one of the two objects partially overlapped the other it was difficult to separate the two images, and the area of contact was very vague in the image of the under one, and when the scrutiny reached that portion the other image returned to its original overlapping position.
IV. SUPPRESSION OF ONE OF TWO IMAGES.
The next tables (V. and VI.) give the results of experiments in suppressing one of two images, the objects presented being saturated color squares, discs, triangles, etc., placed side by side, one above the other, or a smaller one superposed on a larger. The time of perception was five seconds. After the disappearance of after-images, if there were any, the subject was directed to suppress one of the two memory images, the one to be suppressed being indicated by the director. The subject reported as soon as the indicated image disappeared, and reported any return of the suppressed image and its later disappearance in consequence of his efforts. Also he reported any disappearance and reappearance of the retained image. Five minutes was the limit of the time for the experiments with a few exceptions. The times were recorded, and those given for the first suppression include the time between the director's command and the subject's report 'now' or 'gone,' and include, therefore, two reaction times. The later suppressions include but one reaction time.
TABLE V.
SUMMARY OF ALL SUPPRESSIONS. AVERAGE TIME IN SECONDS.
| Image Suppressed | No of Exper. | Time of First Supp. | Time of Ab. of Supp. Im. | No. of Later Supp. | Time of Later Supp. | No. of Ab. of Supp. Im. | Time of Ab. of Supp. Im. | Time of All Supp. | Time of All Absence of Supp. Im. |
|---|---|---|---|---|---|---|---|---|---|
| Right. | 46 | 11.59 | 82.39 | 221 | 8.43 | 216 | 35.74 | 8.94 | 43.93 |
| Left. | 43 | 11.89 | 79.34 | 175 | 7.79 | 173 | 44.86 | 8.60 | 51.26 |
| Upper. | 22 | 11.67 | 49.77 | 150 | 6.26 | 147 | 29.75 | 6.95 | 32.35 |
| Lower. | 17 | 14.23 | 64 | 71 | 7.88 | 70 | 46.68 | 9.11 | 50.04 |
| Central. | 42 | 18.24 | 96.93 | 357 | 3.90 | 352 | 18.13 | 5.41 | 26.54 |
| Marginal. | 20 | 14.25 | 181.57 | 24 | 8.93 | 24 | 78.08 | 11.35 | 125.12 |
| Sundry. | 7 | 8.71 | 127.21 | 19 | 13.34 | 19 | 47.27 | 12.09 | 68.78 |
| Averages. | 13.48 | 91.25 | 6.46 | 32.14 | 7.60 | 41.86 |