Fechner's law refers to named after the German physicist and psychologist Gustav Fechner. Large increases in the intensity of a stimulus produce smaller, proportional increases in the intensity perceived. It is expressed mathematically as S=k log R, where S is the intensity experienced, R is the actual physical intensity and k is a constant. This is one of the first attempts at a mathematical statement of a psychological phenomenon. It grew out of the studies in psychophysics with which psychology became an experimental science in the 1870s.
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