Storia e problemi della psicofisica

This paper illustrates the problems of psychophysics through an historical analysis. The analysis begins with noting that, about 150 years before Christ, Hipparchus of Rhodes was the first to use a psychophysical method to measure the intensity of the sensation of stellar brightness. Astronomers discovered that the relation between this intensity and the corresponding quantity of light measured by the photometer was approximately logarithmic. Fechner proposed that such a logarithmic relation was a psychophysical law valid for all sensations. Alternatively, Plateau proposed that a power function described the psychophysical law. An analysis of these laws shows, however, that they are arbitrary. This conclusion leads to the redefinition of the objectives of psychophysics. These new objectives are illustrated in the context of Anderson’s theory of information integration. Besides the problem of measuring sensory intensity, modern psychophysics faces both the problem of discovering the laws governing the integration of information involved in the generation of sensations and the problem of measuring such information. Curiously, the psychophysical method found today to be adequate for this purpose is the method used by Hipparchus more than 2000 years ago. Finally, philosophical analysis shows that physics and psychophysics share the objective of explaining perceived objects and that, to make these explanations possible, each of these sciences is compelled to make use of imperceptible explanatory principles.