Open peer commentary on the article “Missing Colors: The Enactivist Approach to Perception” by Adrián G. Palacios, María-José Escobar & Esteban Céspedes. Upshot: Palacios, Escobar and Céspedes consider misrepresentation and comparability in the context of the enactivist approach of colour perception. This consideration leads them to propose the introduction of a weak form of representationalism to account for internal representation of “reality” and “shared experience” and to accommodate the Bayesian principle of prior information used in machine vision. The weak representationalism is not limited to brain states but may include embodied factors to be compatible with the enactivist framework. My commentary will essentially consider the misrepresentation and comparability arguments used by the authors to introduce the notion of representation.

We have measured the chromatic threshold sensitivity to stimuli with spectral composition determined by a periodic function of energy over wavelength. This approach is analogous to frequency studies of spatial vision for the study of colour. A device was constructed permitting the synthesis of illuminants over the entire visible range (400–700 nm) in which phase, frequency and amplitude can be independently controlled. We have used 12 frequencies of square-wave functions (from 0.5 to 3.6 cycles/300 nm) and seven values of phase (between 0 degrees and 180 degrees) to obtain the contrast sensitivity function of the chromatic system in three normal trichromats. The results show maximum sensitivity around 1.5 cycles/300 nm and a high-frequency cut-off at 3.6 cycles/300 nm. These empirical values are compared with the predictions obtained from three current psychophysical models of opponent-colour process.