4. The Influence of Size of Objects.
A study of this factor was made possible by substituting for the usual objects steel balls of a smaller size, 1-4 in. The results are contained in Table XX. They are not so striking as those obtained in our study of distribution. Still the influence of this new factor is evident, in the reduction of the apparent number. Olmsted shows this more generally for the smaller numbers. We find it in Hutchison when we compare the new results with the second standard series. This tendency to underestimation increases in the two final series of the present set. At the beginning of these two he remarked that he thought he had been overestimating the group. This tendency of smaller size to reduce apparent number was found true for the majority of observers in our earlier study of relative number.
5. The Influence of the Length of Exposure.
I found that in relative number the shorter the look the more marked was the influence of certain factors. Reports of the observers making this seem highly probable happened in this way: When working with the One-Group Apparatus in relative number the shutter of the camera would occasionally stick, leaving a group exposed beyond its usual time. The effect of this upon some but not all the observers was to cause a noticeable shrinking in numerousness. Of those questioned, the only one failing to notice this effect is included among the observers in this new study.
To test this possibility resort was had to the One-Group Apparatus as affording a more satisfactory means for getting different lengths of exposure of small absolute magnitude. Cards were prepared containing a single group of larger area (67 × 82 mm.) than had been used for relative number. The objects were the usual white circles. Each corner was marked as usual; and, by reason of the number involved, the outline of the area was more regular than had been true in the earlier work. The number of circles on each card varied by steps of two from 16 to 30, giving eight cards in all. The series was arranged irregularly as before, and two of the cards repeated immediately upon their first presentation, making ten experiments in one set. The order of the series follows:
- 1. 24
- 2. 22
- 3. 26
- 4. No change
- 5. 18
- 6. 28
- 7. 16
- 8. 20
- 9. 30
- 10. No change
Two time-magnitudes were used for comparison,—1-25 sec. and 1 sec. The latter was managed with bulb exposure. All the experiments with the shorter time were made before those with the longer had been begun. The results are given in Table XXI. So far as the material is comparable, we may include in our comparison the standard experiments of Tables XIX and XX with 2 sec. exposure.
TABLE XXI
| Baldwin | Miller | Hutchison | Olmsted | ||||||
| Actual Numbers | 125 sec. | 1 sec. | 125 sec. | 1 sec. | 125 sec. | 1 sec. | 125 sec. | 1 sec. | |
| Number of trials with each number | |||||||||
| 5 | 6 | 5 | 5 | 5 | 4 | 4 | 4 | ||
| 16 | 6 | 9 | -2 | -3 | 11 | -1 | 2 | -5 | |
| 18 | 8 | 10 | -4 | -1 | 12 | -1 | -3 | -5 | |
| 20 | 34 | 19 | 1 | 3 | 19 | 1 | 1 | 1 | |
| 22 | 37 | 17 | 6 | 6 | 14 | 6 | 4 | -2 | |
| 24 | 49 | 26 | 12 | 5 | 14 | 10 | 5 | 0 | |
| 26 | 70 | 33 | 15 | 8 | 12 | 9 | 5 | 4 | |
| 26 | 79 | 37 | 21 | 9 | 14 | 4 | 9 | 4 | |
| 28 | 93 | 42 | 29 | 11 | 18 | 7 | 8 | 7 | |
| 30 | 106 | 52 | 38 | 12 | 18 | 5 | 19 | 10 | |
| 30 | 103 | 50 | 45 | 11 | 20 | 4 | 19 | 4 | |
For the meaning of these figures see note under Table XIX.