单项选择题

TEXT D
A Polish proverb claims that fish, to taste right, should swim three times—in water, in butter and in wine. The early efforts of the basic scientists in the food industry were directed at improving preparation, preservation, and distribution of safe and nutritious food. Our memories of certain foodstuffs eaten during the World War II suggest that, although these might have been safe and nutritious, they certainly did not taste right. Nor were they particularly appetizing in appearance or smell. This neglect of the sensory appeal of foods is happily becoming a thing of the past. Now, in the book Principles of Sensory Evaluation of Food, the authors hope that it will be useful to food technologists in industry and also to others engaged in research into problem of sensory evaluation of foods. An attempt has clearly been made to collect every possible piece of in formation that might be useful, more than one thousand five hundred references being quoted. As a result, the book seems at first sight to be an exhaustive and critically useful review of the literature. This it certainly is, but this by no means is its only achievement, for there are many suggestions for further lines of research, and the discursive passages are crisply provocative of new ideas and new ways of looking at established findings^①.
Of particular interest is the weight given to the psychological aspects of perception, both objectively and subjectively. The relation between stimuli and perception is well covered, and includes a valuable discussion of the uses and disadvantages of the Weber fraction in evaluation of differences. It is interesting to find that in spite of many attempts to separate and define the modalities of tastes, nothing better has been achieved that the familiar classification into sweet, sour and bitter. Nor is there as yet any clear-cut evidence of the physiological nature of the taste stimulus. With regard to smell, systems of classification are of little value because of the extraordinary sensitivity of the nose and because the response to the stimulus is so subjective. The authors suggested that a classification based on the size, shape and electronic status of the molecule bear the merit for further investigation, as does the theoretical proposition that weak physical binding of the stimulant molecule to the receptor site is a necessary part of the mechanism of stimulation^②.
Apart from taste and smell, there are many other components of perception of the sensations from food in the mouth. The basic modalities of pain, cold, warmth and touch, together with vibration sense, discrimination and localization may all play a part, as of course, does auditory reception of bone-conducted vibratory stimuli from the teeth when eating crisp or crunchy foods. In this connection the authors rightly point out that this type of stimulus requires much more investigation, suggesting that a start might be made by using subjects afflicted with various forms of deafness. It is well known that extraneous noise may alter discrimination, and the attention of the authors is directed to the work of Prof H.J. Eysenck on the "stimulus hunger" of extroverts and the "stimulus avoidance" of introverts.
Which of the following statements concerning the system of classification in taste is TRUE