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Weber's Law

  1. George H. Robinson

Published Online: 30 JAN 2010

DOI: 10.1002/9780470479216.corpsy1033

Corsini Encyclopedia of Psychology

Corsini Encyclopedia of Psychology

How to Cite

Robinson, G. H. 2010. Weber's Law. Corsini Encyclopedia of Psychology. 1.

Author Information

  1. University of North Alabama

Publication History

  1. Published Online: 30 JAN 2010


Ernst Heinrich Weber (1795–1878), professor of anatomy (1821–1871) and physiology (1840–1866) at the University of Leipzig, on the basis of experiments with stimuli of pressure, lifted weights, and visual distance (line lengths), along with reported observations of others, concluded that, rather than perceiving simply the difference between stimuli being compared, we perceive the ratio of the difference to the magnitude of the stimuli. A similar finding had already been made by the French physicist and mathematician Pierre Bouguer (1698–1758) for visual brightness. Gustav T. Fechner (1801–1887), formerly a student of Weber's and later also a professor at the University of Leipzig, translated this conclusion into the familiar mathematical form used today. Thus Weber's law is usually given as either ΔI/I = k or ΔI = kI, where ΔI is the change required for a just noticeable difference in stimulation (JND), I is the stimulus magnitude, and k is a constant for the particular sense. The value of k is termed the Weber ratio. The equation ΔI = kI shows more clearly the proportional change in stimulation required for a JND. If, for example, the stimulus magnitude is doubled, the amount of change required for a JND is also doubled.


  • Fechner's law;
  • just noticeable differences;
  • sensation