To such suggestions, however, Kuelpe objects that: “There is no indication of a continuous transition between the four qualities which tastes appear to present, as there is between the qualities of tone sensations. They form, not a one-dimensional manifold, but a discrete system of unknown relations.”
Titchener, one of the most careful students of sense experience, is less emphatic, but he “doubts whether, in the present state of our knowledge, this idea (that of Wundt) can be accepted.” He doubts “whether the sweet-sour of lemonade stands to its originals as blue-green stands to blue and green, or as orange to red and yellow; and also whether bitter should lie in the same plane with the other three taste qualities. We must suspend judgment; in the meantime, Kiesow’s figure provides us with a working hypothesis.”
Ladd and Woodworth align themselves with Kuelpe and conclude that, “there is no clear indication that the tastes can be arranged in a linear scale, as the primary colors are, nor that any taste stands to any other definitely in the relation of opposite or complementary. On the whole it appears as if the four tastes were rather isolated from each other, each representing almost an independent sense.”
CHAPTER III
The Sensitiveness of Taste
Various Measures of Sensitiveness
In a general way it is well known that exceedingly weak solutions of many substances are sufficient to provoke sensations of taste. It is also known that weak tastes which some individuals are able to detect or to recognize correctly go quite unobserved by others. The same thing is true of differences between tastes. The connoisseur is sensitive to minute differences in the flavor of wine, tobaccos, and sauces. Through practice the expert taster of these substances acquires a skill which is quite incomprehensible to the inexperienced. In part only is such skill a matter of special sensory activity. It is in large measure a matter of perception rather than one of sensation,—a knowledge of what signs to look for and how to interpret these signs,—rather than an increased sensitiveness to stimuli. In the same way the skilled gardener, hunter, or scout is alert to the significance of particular signs and clues and this alertness and apt interpretation may make him appear to have senses of exceeding acuteness, although this may by no means be borne out by actual measurements.
The psychological problems involved in the measurement of keenness of taste are mainly two in number. One problem concerns itself with the question, What is the faintest stimulus that can be sensed,—the weakest taste that can be appreciated? The other concerns itself with the sensitivity to difference between tastes, and would be expressed by some such question as, How slight a change in the amount or intensity of the stimulus is required for one to be able to perceive a change in the intensity of the taste sensation?
Unfortunately for our knowledge of tastes, both these problems are very difficult to approach experimentally. Whether or not a given weak stimulus will provoke a taste sensation depends on very many things other than the strength of the solution. The amount of solution applied, the extent of surface excited, the duration of the application, the temperature of the solution, the state of rest or movement of the sense organ, and the nature of preceding stimuli, among other things, are important.