Interaction between short- and longer-wavelength cones in hue cancellation codes: nonlinearities of hue cancellation...

Hue cancellation experiments were carried out to test the linear additivity of chromatic valences. There were two kinds of experiments: the measurements of the yellow-blue cancellation function and of the red-green one. The opponent-color equilibria were determined as a function of stimulus intensity for mixture lights of various spectral compositions. The results of the yellow-blue cancellation functions showed that the nonlinearity of the cancellation code strongly depended on the spectral compositions of stimuli: the nonlinearity became evident under conditions producing a relative increase in the long-wavelength-cone excitation, while it was reduced under conditions producing a relative increase in the middle-wavelength-cone excitation. This property could be well explained if we assume that the gain of the short-wavelength signal might be controlled by a difference signal between the long- and middle-wavelength cones. The results of the red-green cancellation functions showed that the cancellation function for a violet light was nonlinear under some specific conditions, while the cancellation function for a red light remained linear. The nonlinearity of the short-wavelength red response became more prominent under conditions producing a relative increase in the long-wavelength-cone excitation. It is suggested that the cone-interaction between the short- and longer-wavelength cones may be responsible for the nonlinearities of the yellow-blue and red-green hue cancellation codes.