Weber’s Law: Why We Miss the Small Changes
Scientifically Reviewed · Dr. Marwa Abd-Alazim · September 26, 2026
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Weber’s law, also known as the Weber-Fechner law, is a psychophysical law established by German physicist Ernst Heinrich Weber and German psychologist Gustav Fechner in the early 19th century. This law states that the magnitude of a stimulus required to produce a given response is proportional to the magnitude of the existing stimulus. In simpler terms, this means that when two stimuli differ from each other, the difference in the magnitude of the stimuli required to produce a response will be proportional to the magnitude of the existing stimulus (Weber, 1834; Fechner, 1860).
This law has been used in a variety of applications, including the study of human perception, sensory physiology, and visual psychophysics. For instance, in the field of psychology, Weber’s law has been used to study how human vision is affected by changes in intensity of light and how humans perceive the differences in brightness or loudness of sound (Fechner, 1860; Stevens, 1975). In the field of sensory physiology, Weber’s law has been used to study the effects of changes in pressure on the perception of pain (Kandel, Schwartz, & Jessell, 2000).
In addition to its application in the field of psychology and physiology, Weber’s law has also been used in the field of economics. Specifically, this law has been used to explain the relationship between the absolute price and the percentage change in price. This is known as Price Elasticity of Demand, which states that the percentage change in demand for a certain good or service will be proportional to the absolute change in price (Hirshleifer, 1971).
Overall, Weber’s law is a fundamental psychophysical law that has been used in a variety of applications across the fields of psychology, physiology, and economics. This law states that the magnitude of a stimulus required to produce a given response is proportional to the magnitude of the existing stimulus, providing an important insight into the way humans perceive and respond to stimuli.
References
Fechner, G. (1860). Elements of psychophysics. Leipzig, Germany: Breitkopf & Härtel.
Hirshleifer, J. (1971). The private and social value of information and the reward to inventive activity. The American Economic Review, 61(4), 561–574.
Kandel, E. R., Schwartz, J. H., & Jessell, T. M. (2000). Principles of neural science (4th ed.). New York, NY: McGraw-Hill.
Stevens, S. S. (1975). Psychophysics: Introduction to its perceptual, neural, and social prospects. New York, NY: John Wiley & Sons.
Weber, E. H. (1834). On the tactual sensibility of the human skin. In G. Fechner (Ed.), Planck’s Treatise on Human Nature (pp. 5–14). Leipzig, Germany: Breitkopf & Härtel.
