Correspondence between Stevens' Terminal Brightness Function and the Discriminability Law

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Science  14 Dec 1962:
Vol. 138, Issue 3546, pp. 1274-1275
DOI: 10.1126/science.138.3546.1274


Stevens' terminal brightness function, an adaptation curve derived from power law data, closely agrees with Troland's just-noticeable-difference (jnd) summation for brightness. The power law itself describes sensation magnitude before adaptation to a test stimulus, whereas the Fechnerian discriminability law describes sensation magnitude after adaptation. This suggests their synthesis in a more general psychophysical equation.