The ability of bisection procedures to specify the form of the psychophysical scale depends upon the precision of the technique. It is demonstrated that this precision is a function of the stimulus interval bisected. The testing of interval scale properties of derived scales is discussed. (Author/JKS)

Psychophysicists neglect to consider how error should be characterized in applications of the power law. Failures of the power law to agree with certain theoretical predictions are examined. A power law with lognormal product structure is proposed and approximately unbiased parameter estimates given for several common estimation situations.…

Thurstone's landmark papers on psychophysics, published in the twenties, are discussed in this presidential address to the Psychometric Society. The development of psychophysics from Thurstone to the present is presented in some detail. (JKS)

A probabilistic choice model, based on L. L. Thurstone's Law of Comparative Judgment Case V, is developed for paired comparisons data about psychological stimuli. The model assumes that each stimulus is measured on a small number of physical variables. An algorithm for estimating parameters is illustrated with real data. (SLD)