On 2016 Nov 10, Lydia Maniatis commented:

The authors assert that their findings: “support the idea that there are density-selective channels in the visual system, and that perceived density is in part based on a comparison of these channel responses across space. “

Looking at the stimuli, I would suggest another interpretation. The areas with more closely grouped dots tend to be seen as figure, and the more dilute ones as ground. This is my impression. If this is the case, we should expect the dense areas to appear even denser, and the less dense areas to appear even less dense because: It has been understood since Rubin that figure appears more dense and ground less so: “According to Rubin (1915/1921), figures…adhere or cling together (are compact)…In comparison, the ground…has a “loose” structure....” (Wertheimer/Spillman Ed. 2012 On perceived motion and figural organization, MIT Press).

There is no obvious functional rationale for positing “density channels” that compare the densities (how is this evaluated?) of adjacent or overlapping surfaces.

On 2016 Nov 10, Lydia Maniatis commented:

The authors assert that their findings: “support the idea that there are density-selective channels in the visual system, and that perceived density is in part based on a comparison of these channel responses across space. “

Looking at the stimuli, I would suggest another interpretation. The areas with more closely grouped dots tend to be seen as figure, and the more dilute ones as ground. This is my impression. If this is the case, we should expect the dense areas to appear even denser, and the less dense areas to appear even less dense because: It has been understood since Rubin that figure appears more dense and ground less so: “According to Rubin (1915/1921), figures…adhere or cling together (are compact)…In comparison, the ground…has a “loose” structure....” (Wertheimer/Spillman Ed. 2012 On perceived motion and figural organization, MIT Press).

There is no obvious functional rationale for positing “density channels” that compare the densities (how is this evaluated?) of adjacent or overlapping surfaces.