On 2016 Oct 22, Lydia Maniatis commented:

As is well-known, perceived color and lightness are contingent on the distribution of luminance/chromaticity in the proximal stimulus and on the corresponding structure of the percept, via the visual process and the principles instantiated therein.

This being the case, any conclusions regarding perceived color contrast that do not explicitly include structure in the discussion will not generalize but will be strictly ad hoc. The results of the present study apply to "plaids", and surely not all plaids, as a category, given the relevance of particular chromaticity values and distributions. The title of the paper, however, implies generality.

The authors also inappropriately leave structure out of the conversation when they speculate that:

"Superimposed luminance and color contrast without co-alignment commonly occurs in natural scenes when shadows or shading fall on a colored surface, whereas co-aligned color and luminance borders are indicative of object and material boundaries, suggesting these two situations activate different color-luminance interactions. "

As descriptions the terms "superimposed luminance and color contrast without co-alignment" and "co-aligned color and luminance borders" are not specific enough, being structure-blind, to assure whether and where "shadows" and "object boundaries" will result in the percept. An easy example, always to hand are the amodally-completed boundaries (which occur in addition to the subjective contours) in the Kanizsa triangle, as well as the appearance of overlap within figures without a luminance step, as well as situations in which the color spectrum or intensity range is shifted and which produce the impression of colored illumination or shading. Whether two areas are interpreted as overlapping ("superimposed" is a description of the percept not the proximal stimulus or the stimulus presented on a screen) depends on relative surface properties and their shapes, not simple "alignments."

So to refer to two different "situations" on the basis of the result - the percept - and to assume different mechanisms ("different color-luminance interactions), without adequately specifying a priori how these two situations are differentiated with respect to the stimulus structure, is putting the cart before the horse.

On 2016 Oct 22, Lydia Maniatis commented:

As is well-known, perceived color and lightness are contingent on the distribution of luminance/chromaticity in the proximal stimulus and on the corresponding structure of the percept, via the visual process and the principles instantiated therein.

This being the case, any conclusions regarding perceived color contrast that do not explicitly include structure in the discussion will not generalize but will be strictly ad hoc. The results of the present study apply to "plaids", and surely not all plaids, as a category, given the relevance of particular chromaticity values and distributions. The title of the paper, however, implies generality.

The authors also inappropriately leave structure out of the conversation when they speculate that:

"Superimposed luminance and color contrast without co-alignment commonly occurs in natural scenes when shadows or shading fall on a colored surface, whereas co-aligned color and luminance borders are indicative of object and material boundaries, suggesting these two situations activate different color-luminance interactions. "

As descriptions the terms "superimposed luminance and color contrast without co-alignment" and "co-aligned color and luminance borders" are not specific enough, being structure-blind, to assure whether and where "shadows" and "object boundaries" will result in the percept. An easy example, always to hand are the amodally-completed boundaries (which occur in addition to the subjective contours) in the Kanizsa triangle, as well as the appearance of overlap within figures without a luminance step, as well as situations in which the color spectrum or intensity range is shifted and which produce the impression of colored illumination or shading. Whether two areas are interpreted as overlapping ("superimposed" is a description of the percept not the proximal stimulus or the stimulus presented on a screen) depends on relative surface properties and their shapes, not simple "alignments."

So to refer to two different "situations" on the basis of the result - the percept - and to assume different mechanisms ("different color-luminance interactions), without adequately specifying a priori how these two situations are differentiated with respect to the stimulus structure, is putting the cart before the horse.