Change. TABLE X. Results of a Rough Attempt to Gauge the Applicability of the Method of Right and Wrong Cases to Smell. Change. Correct judgments of direction. Incorrect judgments Failures to note change Total number of cases. We see that here again the number of mistakes was very large. Yet these were the last experiments made with K., who had worked for us twice a week throughout the year, and who had used butyric ether successfully in experiments by the method of just noticeable differences. He was, however, very tired at the time these last experiments were made. The second stimulus still is more often mistakenly taken for the weaker than for the stronger, showing that in these experiments also exhaustion outweighed adhesion and the timeerror put together. (The tube was cleaned after every eight comparisons.) SUMMARY AND CONCLUSION. In beginning our investigations, we saw that we could not isolate simple olfactory qualities, and that an attempt to prove Weber's law for smell was justified only by the assumption that it might apply to fusions. We also saw that the fact that some olfactory qualities show but few grades of intensity pointed to a rise towards the terminal intensity by geometrical progression. Although Zwaardemaker explains the fact partly by the supposition that different smells have different difference-limina, we believe that two smells with the same difference-limen may exhaust the human sense-organ with very unequal degrees of rapidity, so that one may reach the terminal intensity much sooner than the other. Aside from the condition of the sense-organ, the intensity of a smell depends (1) on the amount of odorous surface exposed to the air, (2) on the time that it is exposed, (3) on the condition of the air in regard to temperature, moisture, etc., which controls the rate of evaporation, (4) on the diffusion-rate of the vapor, and (5) on the rate and manner of the subject's breathing. The great incidental difficulties in olfactometric work are (1) the variability of the organ through obstruction by mucus or (2) exhaustion, (3) the adhesion of the odorous matter to parts of the apparatus, and (4) the presence of compensating smells. The freedom of the nasal passages may be tested, but exhaustion can neither be prevented nor measured, nor can adhesion and the presence of compensating odors be absolutely excluded. We employed Zwaardemaker's olfactometric method in which (1) the measure is the amount of odorous surface exposed, (2) the time of exposure may be disregarded, (3) the diffusion-rate of vapor is under control, and (4) the subject's breathing is supposed to be self-regulating. We did not (5) succeed in regulating the temperature of our laboratory, but its variability was not of primary importance in differencedeterminations. Adhesion makes the method of minimal changes impracticable for most substances with Zwaardemaker's method of smell-measurement, and exhaustion contributes to make the method of right and wrong cases very difficult. We therefore used the method of just noticeable differences. This psychophysical method involves an error from the subject's tendency to judge in terms of hand-movement. Another occasional source of error, incidental to our apparatus, was the escape of some odors between the inhaling-tube and cylinder. Both of these circumstances tend to make the values of Ar smaller for the larger standards. Adhesion and the ordinary time-error tend to balance exhaustion. In spite of the four most serious sources of error, (1) exhaustion, (2) adhesion, (3) the movement-error, and (4) the unmeasured increment to some stimuli, we found to be about 3 in 36% and about r 4 in 26% of our determinations. It was about 1⁄2 in 12%, about in 12%, about in 4%, greater than 1⁄2 in 5% and less than in 5% of the determinations. The slight use we made of the other gradation-methods confirms the general result. There is no great variation from one substance to another, or from one of Zwaardemaker's classes to another. There is much yet to be done and said in olfactometric work -"of making of books there might be no end"-but we believe that enough has been said and done to offer some evidence that Weber's law applies to smell and that the value of Ar lies between one-third and one-fourth. r MINOR STUDIES FROM THE PSYCHOLOGICAL LABORATORY OF CORNELL UNIVERSITY. COMMUNICATED BY E. B. TITCHENER. XVII. CUTANEOUS PERCEPTION OF FORM. By D. R. MAJOR, PH. D. The object of the following experiments was the determination of the limen of form at various parts of the cutaneous surface. Although the investigation is not yet concluded, it seems worth while to publish the results so far gained: especially as there is no literature upon the subject (cf. Henri, Raumw. d. Tastsinnes, 1898, p. 53). The forms employed were angles, open circles, filled circles and filled triangles. The angles (of 35°) were made by fastening strips of sheet rubber to wooden handles. The lengths of side used were 3 to 10 mm., inclusive. The open circles were cut from glass tubing (thickness of glass about .5 mm.), the cut edge of which was ground. The outside diameters ranged between 2 and 11 mm. The filled circles were made from solid glass rods, in the same way: diameters 2 to 12 mm. The triangles (equilateral) were cut from hard rubber blocks, and fastened to wooden handles: sides 2 to 9 mm. In each series the increment of difference was I mm. The method employed was that of just noticeable stimuli, as described by Kuelpe (Outlines of Psych., pp. 55 f.). The subject closed his eyes, and the form was pressed firmly down upon the skin, at the place selected. As soon as the subject had cognised (or definitely failed to cognise) a form, he opened his eyes, and drew upon paper a figure which corresponded to the cutaneous perception. The judgment of cutaneous form was thus recorded in terms of a visual translation. This procedure recommended itself in view of the fact that movement was above all things to be avoided; we were investigating the cutaneous, not the tactual appreciation of form. It may be said at once, however, that one of the subjects (G), who is of the tactual type and has small power of visualization, could hardly be restrained from movement (wrinkling the skin, shifting the fingers, etc.,) in spite of all cautions. With the other two subjects no such difficulty was found. The subjects-Dr. I. M. Bentley (B), Dr. E. A. Gamble (G), and Dr. W. Manahan (M)-were all trained in psychological methods, and knew in a general way the object of the present enquiry. The procedure with knowledge was, of course, followed in experimentation. B soon became aware that only four forms were being employed; G and M showed no trace of any positive opinion on the matter. The surfaces tested were the tip of the tongue, the tip of the middle finger of the right hand, and the central portions of the red areas of upper and lower lips. It was a mistake to work upon all four with the same forms in a single investigation, since information gained from the points of greater discrimination is almost inevitably transferred to other points, whose limina are thus unduly lowered. The results proved that the dimensions taken were not small enough, in the following cases: angles, on the tongue and under lip; open circles, on the tongue; filled triangles, on the tongue. (The results from G, where they stand alone, throw no light on this question, for the reason given above.) On the other hand, the dimensions were too small to allow of liminal determinations on forehead, cheek, ball of thumb, and volar side of wrist. No other surfaces were tried. Results. The following Tables show the results for the three subjects on the four surfaces. Under L is given the average form limen; under m. v. the average departure of the single determinations from L; under no. the number of single determinations made. It must be remembered that a single determination implies the performance of experiments in two directions, ascending and descending; so that, e. g., 10 L's required 20 series of experiments. The m. v.'s of the partial limina were very small; hence neither they nor the limina themselves are shown in the Tables. The thick figures indicate that the limit of the instrument was reached, or, in other words, that the recorded L may be too large. 1On tongue and lips these figures were placed always with the apex pointing upwards or downwards upon the longitudinal axis of the body. Variation of direction made no difference in judgment. On It appears from these Tables that, within the limits of our experiments, the surfaces tested rank, as regards capacity of form cognition, in the order: tip of tongue, tip of finger, lips. (Between upper and lower lip there is no appreciable difference.) It appears further, that the cutaneous surfaces differ in their behavior according as the stimuli are surfaces or outlines thus the lips are at a disadvantage when the filled circle and the triangle are applied. A different selection of stimuli might therefore lead to a different order of rank. The fact is brought out in Table V, which is obtained by massing the results from the three subjects. the finger tip, all four possible positions were employed. Unfortunately, we have no separate records for the longitudinal and transverse directions. The introspective notes, however, show (for all three subjects) that cognition was subjectively a little easier when the forms lay transversely upon the surface. JOURNAL-IO |