Stevens' power law

Author: Leandro Alegsa Creation date: November 13, 2022

Stevens' power law is a proposed relationship between the magnitude of a physical stimulus and the intensity or strength that people feel.

Most people think that it describes a wider range of sensations than Weber-Fechner law. But critics argue that the validity of the law is not sure.

The theory is named after psychophysicist Stanley Smith Stevens (1906–1973). Although the idea of a power law had been suggested by 19th century researchers, Stevens is credited with reviving the law and publishing a body of psychophysical data to support it in 1956.

The general form of the law is

\psi (I)=kI^{a},\,\!

where $I$ is the magnitude of the physical stimulus, $\psi$ is the psychophysical function capturing sensation (the subjective size of the stimulus), $a$ is an exponent that depends on the type of stimulation and $k$ is a proportionality constant that depends on the type of stimulation and the units used.

The table to the right lists the exponents reported by Stevens.

Questions and Answers

Q: What is Stevens' power law?

A: Stevens' power law is a proposed relationship between the magnitude of a physical stimulus and the intensity or strength that people feel. It suggests that there is a correlation between these two factors, which can be expressed in the form of an equation.

Q: Who developed this theory?

A: The theory was developed by psychophysicist Stanley Smith Stevens (1906–1973). Although the idea of a power law had been suggested by 19th century researchers, Stevens is credited with reviving it and publishing data to support it in 1956.

Q: How does the general form of the law look like?

A: The general form of the law takes the following form: ψ (I)=kI^a, where I is the magnitude of the physical stimulus, ψ is the psychophysical function capturing sensation (the subjective size of the stimulus), a is an exponent that depends on type of stimulation and k is a proportionality constant that depends on type of stimulation and units used.

Q: What does Weber-Fechner Law describe?

A: Weber-Fechner Law describes how people perceive changes in stimuli such as sound or light intensity. It states that when there are small changes in intensity, people will not perceive them unless they are large enough to cause noticeable differences.

Q: Is validity of Steven's Power Law certain?

A: Critics argue that validity of Steven's Power Law has yet to be proven conclusively.

Q: What exponents have been reported by Stevens?

A: The table accompanying text lists exponents reported by Stevens for different types of stimulations.