Abstract
Many of the laws and empirical observations of fundamental psychophysics can be unified with a single equation, which has been called the complete form of Fechner’s law. It can be shown that this law embraces both of the commonly used forms: Stevens’s and Fechner’s laws. It assumes one or the other form with appropriate values of the parameters. However, the complete equation confers an advantage beyond simply containing the classical laws. It offers greater flexibility in the representation of experimental data. It is shown that psychophysical phenomena may be represented by any number of triplets of quantities: subjective magnitude of stimulus, subjective just noticeable difference (jnd), and differential threshold. Each of the preceding quantities are functions of the physical magnitude of the stimulus. The investigator has the license to choose two of these quantities in the form he or she thinks is best; the third quantity is determined by the choice of the first two. Thus, for example, different forms of the law of sensation and different forms of the mathematical function for differential threshold may coexist with equal validity.
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This research has been supported by an operating grant from the Natural Sciences and Engineering Research Council of Canada. W.W. has been supported by a University of Toronto Open Fellowship. K.H.N. is a member of the Institute of Biomedical Engineering, the Departments of Physiology and Physics at the University of Toronto. W.W. is a member of the Institute of Biomedical Engineering and the Department of Physics at the University of Toronto.
An erratum to this article is available at http://dx.doi.org/10.3758/BF03211927.
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Norwich, K.H., Wong, W. Unification of psychophysical phenomena: The complete form of Fechner’s law. Perception & Psychophysics 59, 929–940 (1997). https://doi.org/10.3758/BF03205509
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DOI: https://doi.org/10.3758/BF03205509