Discriminal Sensitivity on the Subjective Continuum

SUMMARY

(1)	It is pointed out that the relation between discriminal sensitivity and perceived intensity in the subjective dimension is an important problem which has attracted too little attention. There seems to be no single investigation directly centering on this question.
(2)	A method is developed for investigating this relation. It is essentially a graphic procedure for differentiating R with respect to S in order to make possible a computation of discriminal dispersions or related measures in terms of R.
(3)	The method is applied to a fictitious numerical example.
(4)	The same method is applied to published experimental data. It is found that the difference limen is an increasing linear function of intensity in the case of subjective weight, and an increasing, definitely non-linear function in the case of subjective salt intensity.
(5)	There is indirect evidence that the difference limen in subjective units is constant in the case of brightness and pitch, but is an increasing function of intensity in the case of loudness.
(6)	The case of qualitative or inter-dimensional variation is discussed. There is indirect evidence that subjective sensitivity is constant along the curvilinear continuum in the multidimensional subjective space of hue.
(7)	An hypothesis advanced by Stevens and collaborators is contradicted by brightness data but supported by color data.
(8)	Relations between sensitivity and position in the subjective continuum may possible be ascribed to central processes, which makes them more promising objects of investigation than conventional psychophysical relations which also depend on highly specific peripheral factors.