On the protheticity of olfactory pleasantness and intensity

In Exp. 1, the "protheticity" of the pleasantness of a diverse set of relatively isointensive odorants was estimated using exponents from power functions fitted by an interative least squares procedure between scale values established by (a) magnitude estimation and (b) category rating and rank ordering. In Exp. 2, this procedure was applied to intensity data derived from quarter-log-step volume dilution series of two hedonically disparate odorants, furfural and methyl salicylate. The goodness of fit of the power functions was somewhat better for the intensity than for the pleasantness data. The pleasantness dimension of the diverse stimuli was slightly prothetic (respective category scaling and rank order/magnitude estimation exponents = 0.60 and 0.63). The intensity dimension of furfural was considerably more prothetic than that of methyl salicylate (respective category/magnitude estimation exponents = 0.20 and 0.68; respective rank order/magnitude exponents = 0.21 and 0.69). These data suggest that the degree of olfactory protheticity depends upon the stimuli as well as the attributes chosen for investigation and support the view that Stevens' metathetic/prothetic dichotomy has little utility in classifying the scaling attributes of odors. Whether the degree of protheticity reflects the nature or distribution of olfactory system receptive elements within the main olfactory pathway remains an empirical question which awaits a more specific understanding of the nature of olfactory coding at the level of the neuroepithelium.