the organism, and also in terms of the role of the thermal system in informing us concerning the thermally conductive nature of surfaces and substances. He also examines issues in thermal hedonics. He treats the psychophysics of thermal sensitivity in detail, touching on thermal adaptation phenomena. We thus obtain a detailed picture of how the skin and its various receptor systems may function to signal the CNS concerning thermal changes and differences. This can be extremely important not only in avoiding or minimizing tissue damage, but in discovering other objective or hedonic properties of objects, surfaces, and substances.
Although issues of pain perception are mentioned by authors of other chapters, Rollman takes us deeper into a topic that can be as fascinating as the painful experience can be unpleasant, that is, our sensitivities to pain and painful aspects of certain forms of stimulation. Rollman stresses the impact of cognition and emotional factors in the description and evaluation of stimulation as painful, and their roles in pain alleviation. He also examines receptors and their physiology, as well as the relevant spinal tracts, subcortical and cortical areas of the brain in pain. His discussion amplifies the questionable aspects of simple one-to-one models of punctate skin sensitivity, or even sensation-receptor specificity, in the context of a voluminous catalog of receptor types and their relationship to pain. Any strong tactile sensation can be experienced as pain, including those derived from thermal stimulation, pressure, and chemicals. A further difficulty in pain research has been to clarify the relationships between stimulation and CNS transmission lines (e.g., spinal mechanisms), and it is here that specificity has failed to provide all of the answers. Clinical topics relating to pain alleviation are discussed in detail from both methodological and practical standpoints, with specific attention to various sources of pain.
Researchers on pain are confronted with difficult, but important paradoxes. Pain is a "subjective" phenomenon, but we often try to measure it "objectively." Rollman has tried to come to grips with a number of important theoretical and applied issues in pain perception.
We should point out that there are alternative ways to conceptualize touch, and active movement can modify sensory experiences ( Coquery, 1978). It is rather difficult to tickle oneself! In addition, movement may help to organize sensory experience.
Coquery J. ( 1978). "Role of active movement in control of afferent input from skin in cat and man". In G. Gordon (Ed.), Active touch. Oxford, England: Pergamon Press.
Gibson J. J. ( 1966). The senses considered as perceptual systems. Boston: Houghton Mifflin.