Fechner, Gustav Theodor
Gustav Theodor Fechner was a German experimental psychologist and philosopher. He is also considered by many to be the father of modern psychophysics. Initially, Fechner took a degree in medicine and worked in that area for a while. During that time he began publishing a series of humorous and satirical articles and poems lampooning the medical profession. These were published under the pseudonym Dr. Mises, and one of his most famous publications of this genre was on the Comparative Anatomy of Angels (1825). The writings of Dr. Mises certainly provide insight into the breadth and depth of Fechner’s intelligence and abilities.
Fechner then moved on to physics by learning about contemporary advances in electricity and magnetism through translation of great French works as well as handbooks of chemistry and physics into German. With this new knowledge in hand, Fechner taught at the University of Leipzig, eventually obtaining a professorship and making distinguished contributions to the field. Interestingly, Dr. Mises also continued to publish on occasion.
All along, Fechner was interested in the mind-body problem and desired to determine an empirical relationship between the physics of the world (and body) and the perceptions of the mind. Some of his studies in this vein included the discovery of perceived colors for slowly flickering black-and-white patterns (known as Fechner’s Colors or Fechner-Benham Colors after Benham made the work accessible in English) and the detailed study of color afterimages. It was the study of afterimages that set Fechner off in his next direction. He was studying afterimages by staring at the sun through colored filters. This led him to give up his chair in physics in 1840 due to induced photophobia from eye injuries that made him an invalid, and overly sensitive to light, for about a decade.
During this period, on October 22, 1850, while lying in bed he finally figured out the basis of linking physical measurements in the environment with human perceptions in the mind that is currently referred to as Fechner’s law. Based on his knowledge of Weber’s law (coined by Fechner) that, for many perceptions, the ratio of a just-noticeable change in a stimulus to the initial magnitude of a stimulus is a constant, Fechner figured out that the differential equation implied by Fechner could be integrated and assumed that the just-noticeable differences could be summed to predict perceptual magnitude. The resulting relationship, now termed Fechner’s law, mathematically suggested that the magnitude of a perception would be proportional to the logarithm of the stimulus intensity.
More modern knowledge tells us that the specific relationship depends on the perceptual quantity and that it is not valid to sum JNDs to predict magnitudes. Nonetheless, Fechner’s contribution was very significant in founding the field of psychophysics. Fechner published further details of the theory and practice of psychophysics in his seminal work, Elements of Psychophysics (1860),  which remains a useful guide for practitioners in the field. Interestingly, Fechner is also credited with being the first to introduce the concept of the median to formal data analysis.
From Boring’s introduction in Adler’s translation of Elements of Psychophysics, we find that Fechner was for 7 years a physiologist (1817–1824), for 15 years a physicist (1824–1839), for 12 years an invalid (1839–1851), for 14 years a psychophysicist (1851–1865), for 11 years an experimental estheticist (1865–1876), and for periods throughout a philosopher.
- 1.G. Fechner: Elements of Psychophysics (trans.: H. E. Adler). Holt, Rinehart and Winston, New York (1966)Google Scholar