Quantitative judgments of color: The square root rule

Visual intensity judgments: An empirical rule and a theory.

“…In order to test the validity and generality of the square root rule for color, Warren (1967) employed six different colored papers (2 greens, 2 reds, a blue, and a purplish blue) mixed with white. As in the earlier experiments by Richardson and by Maxwell, 5s viewed a rapidly rotating disk (see Figure 1).…”

“…By maintaining colorimetric simplicity and changing only saturation of color, complex psychophysical scales were obtained, with different functions found by the same investigators for different colors, and different functions found by different investigators for the same colors. Warren (1967) pointed out that lightness (or brightness) and saturation do not function as independent variables in psychophysical judgments, but rather that integration of sensory input occurs without analysis into what would be considered as component elements in the Munsell system. However, the Ostwald system (constructed by the Nobel laureate German chemist) does employ a color notation consistent with the experiments by Richardson, Maxwell, and myself, so that with this system it is possible to vary white content for a constant hue along a single continuum.…”

Nonlinear cortical encoding of color predicts enhanced McCollough effects in anomalous trichromats

“…Second, measurements of 'perceived' saturation by magnitude estimation are consistent with a compressively nonlinear relationship between physical and perceived saturation' (e.g. Indow and Stevens, 1966;Warren, 1967). Third, evidence from visually evoked potentials (Rabin et al, 1994;Porciatti and Sartucci, 1999) and fMRI (Wandell et al, 1999;Tregillus et al, 2020) shows a compressive nonlinearity in the neural representation of chromatic contrast.…”