INTENSITY RESOLUTION AND SUBJECTIVE MAGNITUDE IN PSYCHOPHYSICAL SCALING

Several successful theories of psychophysical judgment imply that expo nents of power functions in scaling tasks should covary with measures of intensity resolution such as d' in the same tasks, whereas the prev ailing metatheory of ideal psychophysical scaling asserts the independ ence of the two. In a direct test of this relationship, three prominen t psychophysical scaling paradigms were studied: category judgment wit hout an identification function, absolute magnitude estimation, and cr oss-modality matching with light intensity as the response continuum. Separate groups of subjects for each scaling paradigm made repeated ju dgments of the loudnesses of the pure tones that constituted each of t wo stimulus ensembles. The narrow- and wide-range ensembles shared six identical stimulus intensities in the middle of each set. Intensity r esolution, as measured by d'-like distances, of these physically ident ical stimuli was significantly worse for the wide-range set for all th ree methods. Exponents of power functions fitted to geometric mean res ponses, and in magnitude estimation and cross-modality matching the ge ometric mean responses themselves, were also significantly smaller in the wide-range condition. The variation of power function exponents, a nd of psychophysical scale values, for stimulus intensities that were identical in the two stimulus sets with the intensities of other membe rs of the ensembles is inconsistent with the metatheory on which moder n psychophysical scaling practice is based, although it is consistent with other useful approaches to measurement of psychological magnitude s.