When1: 1820
When2: 1846
Who: Ernst Heinrich Weber [Weber, Ernst Heinrich]
What: physiologist
Where: Leipzig, Germany
works\ On vision and hearing in humans and animals [1820]; Additions to the Theory of Construction and Function of the Genital Organs [1846]
Detail: He lived 1795 to 1878, studied psychophysics, invented theory of signs {Lokalzeichentheorie}, measured skin sensitivity to separated stimuli [1826], studied inhibition by vagus nerve [1845], and developed law of sensation [1834], with Fechner. People can distinguish between two similar sensations {just-noticeable difference}. For each sense, ratio of just-noticeable-difference to intensity is approximately constant for all intensities. Subjective sensation increases as logarithm of physical-stimulus magnitude. Just-noticeable difference increases in direct proportion to stimulus intensity. If I is sensation intensity, intensity change divided by intensity equals constant {Weber-Fechner law} {Weber's law}: (I2 - I1) / I1 = Weber's constant. Weber's constant {Weber fraction} represents smallest stimulus intensity difference that people can perceive. If intensity is higher, differences must be larger for people to perceive them. Weber's constant is typically greater than one to three percent, differs for different senses, and tends to increase with age.
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Date Modified: 2022.0224