We·ber \ˈvā-bər\ Ernst Heinrich (1795–1878), German anatomist and physiologist. Weber undertook studies of the sense of touch that are important to both psychology and sensory physiology. He introduced the concept of the just noticeable difference between two similar stimuli. In 1851 he published an expanded report on his experimental findings on the sense of touch. Some consider this work to mark the founding of experimental psychology. Weber's empirical observations were expressed mathematically by Gustav Fechner.
Fech·ner \ˈfeḵ-nər\ Gustav Theodor (1801–1887), German physicist and psychologist. Fechner was one of the founders of the science of psychophysics. He brought out a fundamental work in this field in 1860 which established his lasting importance in psychology. Fechner also developed experimental procedures for measuring sensations in relation to the physical magnitude of stimuli. In particular he formulated an equation to express Weber's theory of the just noticeable difference. Subsequent research has revealed that the equation is applicable within the middle range of stimulus intensity and then is only approximately true.