5.49 psychophysical power law; Stevens power law. Description of the relationship between stimulus magnitude and the resulting sensation magnitude. Mathematically,
where Ψ is sensation magnitude, ∅ is stimulus magnitude, ∅0 is the absolute threshold, n is a constant related to a given sense modality, and k is a proportionality constant.
Annotation The psychophysical power law replaces the Weber-Fechner equation (see 5.64) which held that equal stimulus ratios corresponded to equal sensation differences. The psychophysical power law states that equal stimulus ratios correspond to equal sensation ratios.« Back to Standards Terminolgy Index