SENSORY RECEPTION, HUMAN

means by which the human organism reacts to changes in the external and internal environments. Ancient philosophers called the human senses the windows of the soul, and Aristotle enumerated at least five sensessight, hearing, smell, taste, and touchand his influence has been so enduring that many people still speak of the five senses as if there were no others. Yet, the human skin alone is now regarded as participating in (mediating) a number of different modalities or senses (e.g., hot, cold, pressure, and pain). The modern sensory catalogue also includes a kinesthetic sense (sense organs in muscles, tendons, and joints) and a sense of balance or equilibrium (so-called vestibular organs of the inner ear stimulated by gravity and acceleration). In addition, there are receptors within the circulatory system that are sensitive to carbon dioxide gas in the blood or to changes in blood pressure; and there are receptors in the digestive tract that appear to mediate such experiences as hunger and thirst. Not all receptors give rise to direct sensory awareness; circulatory (cardiovascular) receptors function largely in reflexes that adjust blood pressure or heart rate without the person being conscious of them. Though perceptible as hunger pangs, feelings of hunger are not exclusively mediated by the gastric (stomach) receptors. Some brain cells may also participate as hunger receptors. This is especially true of cells in the lower parts of the brain (such as the hypothalamus) where some cells have been found to be sensitive to changes in blood chemistry (water and other products of digestion) and even to changes in temperature within the brain itself. Additional reading E.G. Boring, Sensation and Perception in the History of Experimental Psychology (1942), a classic historical account of the early work in sensation and perception; John Field (ed.), Handbook of Physiology, section 1, Neurophysiology, vol. 1 (1959), a technical and detailed review of modern sensory physiology; F.A. Geldard, The Human Senses (1953), a scholarly overview of the senses, suitable as an introduction to the subject; D.R. Kenshalo (ed.), The Skin Senses (1968), a specialized report of a symposium held in 1968 that gives the reader with a special interest in this field a good idea of modern research; P.M. Milner, Physiological Psychology (1970), an advanced textbook in general physiological psychology with a good section on the senses; C. Pfaffmann (ed.), Olfaction and Taste, III (1969), a somewhat specialized but good overview of research in olfaction and taste; J.S. Wilentz, The Senses of Man (1968), an excellent popular account for the general reader that serves as a good introduction to the field. Later monographs on human sensory physiology include discussions of modern theories of pain and on space perception, in addition to traditional studies of smell, taste, vision, and hearing. See Christiaan Barnard and John Illman (eds.), The Body Machine (1981); Herbert Hensel, Thermal Sensations and Thermoreceptors in Man (1982); Trygg Engen, The Perception of Odors (1982); Ronald Melzack and Patrick D. Wall, The Challenge of Pain, rev. ed. (1983); Lawrence Kruger and John C. Liebeskind (eds.), Neural Mechanisms of Pain (1984); Herbert L. Pick, Jr., and Linda P. Acredolo (eds.), Spatial Orientation: Theory, Research, and Application: Proceedings of a Conference on Spatial Orientation and Perception, July 1416, 1980 (1983); R. Robin Baker, Human Navigation and the Sixth Sense (1982); Michael Potegal (ed.), Spatial Abilities: Development and Physiological Foundations (1982). Carl Pfaffmann