Published Online: 30 JAN 2010
Copyright © 2010 John Wiley & Sons, Inc. All rights reserved.
Corsini Encyclopedia of Psychology
How to Cite
Robinson, G. H. 2010. Fechner's Law. Corsini Encyclopedia of Psychology. 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°).