| Order of Æsthetic Value | Number of Discriminable Qualities | Sharpness of Discrimination | Average Speed of Reaction | Average Duration of a Sensation, Degree of Inertia |
| Sight | About 40,000 | Difference of 1% | .189 sec. | About .030 sec. |
| Hearing | About 15,000 | Difference of 33% | .146 sec. | About .002 sec. |
| Smell | Nine classes, each with hundreds of qualities | Difference of 25% | Difficult to determine | Very long and difficult to determine |
| Touch | Three or four classes with qualities no easily determined | Difference of 33% | .149 sec. | .001 to .002 sec. |
| Taste | Four classes with number of qualities not determined | Doubtful | .300 sec. to 1.000 sec. | Very long and difficult to determine |
| Kinæsthetic (Movement, Strain, etc.) | Four or five classes with number of degrees not determined | Difference of 5% | Difficult to determine | Undetermined |
| Temperature | Two classes, degrees not determined | Variable and difficult to determine | .150 sec. to .180 sec | Difficult to determine |
| Organic | About six classes | Unknown | Unknown | Unknown |
It requires only a glance at this table to reveal the fact that we possess much more definite knowledge about sight and hearing in these respects than we do about the other modes of sensation. In the case of these two senses, the four characteristics indicated in the table can be stated with considerable precision and certainty. But in the case of the other senses, and of taste in particular, only broad and vague statements can be made, for the most part. Even the number of discriminable qualities which these senses afford is unknown, and statements concerning the other properties are mainly confessions of difficulty or ignorance. It is difficult to judge to what degree this state of affairs is due simply to the greater attention that has been given to sight and hearing in precise psychological investigation, and to what degree it is due to difficulties inherent in the nature of the sense impressions afforded by the other modes. Nevertheless, it is apparent that no one of the special characteristics indicated in the table can be held responsible for the sharp cleavage commonly made between the worthy and the ignoble senses. Consideration of the characteristics in detail shows that we must look elsewhere for the reasons why the lower senses are unæsthetic, and even, perhaps, for the reasons why they are lower.
With respect to number of discriminable qualities, for instance, sight and hearing, with their many thousand distinguishable degrees of impression, might seem to afford such an abundance of raw material that this alone would explain why the principal fine arts have come to be based on these senses. But it must be pointed out that this enumeration of qualities has reference only to the definitely identifiable, classifiable, and controllable degrees of impression. The mere fact that odors can be classified under only nine headings, to which general terms can be given, does not at all mean that there are but nine distinguishable smells. Almost every different object in the world has its own characteristic odor. We have not developed abstract names for these odors, to be sure. We are usually content to designate the odor by the name of the object with which it is associated. And when one bears in mind the multitudinous variations of these odors, their different intensities, mixtures, and modifications, one is inclined to believe that it is only the infinite variety of smell experiences that prevents our enumerating, classifying, and designating them. And what has just been said of smell is equally true of touch, taste, and organic sensations. It is also true that the separate lower senses are seldom stimulated independently,—thus taste is always accompanied by smell, touch, temperature, etc. May it perhaps be true that the very fact that these impressions cannot be estimated, isolated, and reproduced at will has something to do with their inferior æsthetic value? However this may be, it is clear that the mere variety of impressions afforded is not the criterion of which we are in search.
One might be tempted to suppose that the sharpness of discrimination of the various senses, the keenness with which differences in the strength and intensity of impressions can be detected, might be an important factor in determining their availability for æsthetic manipulation. The figures given in the table under this heading indicate the proportion that must be added to a stimulus in order to make it just perceptibly more intense. The temptation is removed at once by a mere inspection of the values. Sight is, to be sure, the most delicate of the senses in this respect, as it is also in number of isolable qualities. But kinæsthetic sensation follows close upon it, while smell stands third in the list, and hearing is no more sensitive than pressure. In the case of taste and the other senses the values are unknown or difficult to determine, but it is clear that the æsthetic values of the different senses do not depend merely on their various psychophysical constants.
The quickness with which one can react to or perceive impressions from the various senses discloses much the same state of affairs. Basing our comparison on the average reaction times to the most commonly available impressions and intensities in each case, hearing, touch, and temperature are seen to be about equally prompt, while sight stands fourth on the list. With respect to the period of time through which a sensation continues to persist, the so-called “life span” of an impression, only three of the values, those for sight, hearing, and touch, have been determined, and these bear no significant relations to each other. But these times are all very short, and the corresponding modes of sensation stand high in the æsthetic scale. The other values, although not determined, are known to be much longer than these. Is it possible that the sluggishness of these senses and the persistence of impressions once set up through them is so great that the impressions do not submit to the forms, patterns, and structures which constitute artistic treatment? Or may it not be equally true that the fugitive character of impressions from the higher senses is what has made necessary the development of treatment by means of pattern and structure?
The Tendency to Adaptation
Suggested by this question of “life span” of sensations is another characteristic which one might expect to find important,—viz., what we have in an early chapter referred to as the “tendency to adaptation” of the different senses. In the case of odors, temperatures, and contacts, we easily and speedily become adapted to continuous presence of impressions and cease to be aware of their existence. Thus, we soon become adapted to the presence of hats on our heads, the clothes on our backs, the smell of smoke, and even to such extreme temperatures as that of the stoking room. Continuous stimulation of one of these senses so raises the threshold of the sense organ that the original stimulus ceases to be effective. So far as practical and æsthetic purposes are concerned, we are then fatigued to the particular impression. We may be gratified to find that this tendency to adaptation is not nearly so conspicuous in the case of sight. But we will be equally dismayed to learn that the tendency is as prominent in the case of hearing as it is in the so-called lower senses. Moreover, this tendency refers to continued stimulation of the same degree or quality, whereas in æsthetic manipulation the qualities presented are varied from moment to moment and from point to point.
Spatial Attributes of Taste Qualities
On the whole, then, these strictly psychological or psychophysical comparisons are so unsatisfactory that we are compelled to look elsewhere for the criteria of the raw material of æsthetics. Some writers have suggested that the absence of definite and formal spatial attributes and systems is what makes certain of the senses unsuitable for æsthetic treatment. But there are two important objections to this suggestion. One is our earlier question as to the reasons why æsthetic treatment should necessarily consist of arrangement in spatial and temporal series and patterns. Unless some excellent reason to the contrary is given, we are free to assume that this is not a necessity, but merely an incidental result, following from the character of the materials, which, for other reasons, for which we seek, are chosen as the raw materials for æsthetic treatment. The other objection, which is, perhaps, more convincing, is the fact that, whereas touch and kinæsthetic impressions both possess immediate voluminousness and take their place readily in a spatial manifold of position, direction, distance, and form, they do not yield to æsthetic treatment; while sound and taste, one of which easily ranks second and the other of which belongs low down in our æsthetic scale, possess extent in only a very doubtful and probably analogical manner, and are almost, if not wholly, lacking in those qualities which would enable them to participate in a manifold of position, direction, distance, and form. As for temporal attributes, such as duration and sequence, all impressions possess them, from whatever sense they originate. The idea that the difficulty or impossibility of giving spatial and temporal form to the lower sensations prevents the representation of nature by means of them, and that this is a sufficient reason for regarding them as inferior is anything but adequate.