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Fechner's Law

  1. George H. Robinson

Published Online: 30 JAN 2010

DOI: 10.1002/9780470479216.corpsy0350

Corsini Encyclopedia of Psychology

Corsini Encyclopedia of Psychology

How to Cite

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

Author Information

  1. University of North Alabama

Publication History

  1. Published Online: 30 JAN 2010


Gustav T. Fechner (1801–1887), professor of physics at the University of Leipzig, sought to measure the mind quantitatively. In approaching this task he studied stimuli and the sensations they aroused. His interest was in ascertaining how sensations changed with changing stimulation. While lying in bed on the morning of October 22, 1850, he conceived the essential idea of what was later to be called Fechner's law. In his subsequent derivation of the law (which appears at the beginning of the second volume of Elemente der Psychophysik), he began with Weber's law (that the just-noticeable difference in stimulation is a constant proportion of the stimulus magnitude, or JND=kI) and the assumption that the sensation (R) of a stimulus is the cumulative sum of equal sensation increments. Translating this into differential form, he started with dR = dI/I and integrated, under the assumption that R = 0 at absolute threshold (I°), to get the equation R = clog (I/I°).