The Weber–Fechner law: A misnomer that persists but that should go away.

The term “Weber–Fechner law” is arguably the most widely used misnomer in psychological science. The unification reflects a failure to appreciate the logical independence and disparate implications of Weber’s law and Fechner’s law as well as some closely aligned ones. The present statement, long overdue, is meant to rectify this situation. I discuss the roots and derivations of the relevant laws, eschewing formalism to bare essentials for sake of wider accessibility. Three of the most important conclusions are (a) Weber’s law is not indispensable for deriving Fechner’s law; (b) arguably, Fechner himself did not use Weber’s law in his original derivations; and (c) many investigators mistake the principle that subjective distance is determined by physical ratio for Weber’s law. In truth, the principle, here called the Weber principle, and Weber’s law, are different and independent. I stress the importance of drawing the distinction and illustrate confusions in the literature coming from misapplications of Weber’s law and the use of misnomer.