Zwaardemaker concluded that for a standard of from 2 to 5 cm., the difference limen was about 1.5 cm., and that for a standard of from 5 to 9 cm., it was about 3–5 cm. This would make the value of Δr⁄r ruu from about 1⁄3 to about 3⁄4. Our own results agree fairly well with his, and are a very pretty confirmation of the results obtained by the method of just noticeable differences. The writer intends to use the method of minimal changes much farther.
In contrast with these excellent results are those of the next Table:
Table IX.
Results obtained by the Method of Right and Wrong Cases.
SUBJECTS—C., D., K., ROB., ROG., AND T.
Instrument—Standard Olfactometer. Substances—Black Rubber or Tolu Balsam.
| r AND r1. | Right Cases. | Wrong Cases. | Mistakes Made in Taking the Second Stimulus for Weaker when Stronger. | Total Number of Cases. |
| 20 and 25 | 37 | 19 | 12 | 56 |
| 50 and 70 | 30 | 30 | 9 | 40 |
| 20 and 30 | 47 | 19 | 12 | 66 |
| 30 and 50 | 33 | 11 | 5 | 44 |
| 20 and 40 | 42 | 22 | 18 | 64 |
| 30 and 60 | 4 | 2 | 6 | |
| 20 and 50 | 39 | 11 | 8 | 50 |
| 20 and 60 | 7 | 1 | 1 | 8 |
The stimuli given were never equal, and the judgment “equal” was counted a mistake, The results of all the subjects are massed.
As we said before, while exhaustion makes the errors nearly all run in one direction, confusion due to the unfamiliarity of olfactometric work is probably most at fault, More experiments should be made with the standard olfactometer and trained subjects. It is difficult to use the large olfactometer with this method, because the intervals between stimuli must be made very long or the subject can guess from the time spent in manipulation how they have been changed.
As a rough method of testing the applicability of the method of right and wrong cases to smell, we blind-folded one subject, stopped his ears with absorbent cotton, and required him to tell which way we had moved from a given standard on the large olfactometer. The results are given in the following Table :
