Jozef J. Zwislocki Institute for Sensory Research Syracuse University
On this occasion it seems to me appropriate to begin my chapter with a tribute to Smitty Stevens and to take his work on psychological scaling as a point of departure for my discussion of what I have called natural measurement. Stevens may have been the most important psychophysicist after Fechner, for he seems to have realized Fechner's psychophysical goal by successfully relating the magnitudes of subjective impressions to the magnitudes of physical stimuli that evoke them ( Stevens, 1975, for review). He spent a considerable effort on convincing his peers in both psychology and physics that subjective impressions are accessible to empirical measurement on ratio scales. If he was not entirely successful, the difficulty seems to have stemmed in part from the Zeitgeist to which he was not entirely immune. Although he attempted to liberalize the definition of measurement to suit his purpose, he accepted its essence from Bertrand Russell and Norman Campbell -- measurement is assignment of numbers to things or events according to rules ( Stevens, 1951). He seems to have distanced himself partially from this definition in his last monograph, but he did follow it through much of his experimental work, in particular, when he introduced his revolutionary methods of magnitude estimation and magnitude production ( Stevens, 1956, Stevens & Greenbaum, 1966). However, the definition was made to order for physics after physics had emancipated itself from philosophy and almost automatically excluded psychology. When Stevens ( 1946) proposed to relax the rules to include psychology, physicists objected.
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