[kazinator]

I don't intuitively understand any illusion. I don't have conscious introspection into what the layers of neurons are doing between the retina and conscious visual perception. The layers of neurons use certain indirect cues in order to detect size, depth and movement. Those cues do their job in most circumstances, but test cases can be constructed which falsely trigger those cues. That's just an intellectual generality that doesn't explain anything specific.

[btilly]

You should add shadow to the list of important cues. Something light in shadow can be the same color as something white in direct light. You can see that optical illusion in https://en.wikipedia.org/wiki/Checker_shadow_illusion.

My favorite example of where shadow matters is "the dress". As https://slate.com/technology/2017/04/heres-why-people-saw-th... explains, those whose brains assumed it was in shadow saw it as white and gold. Those whose brains thought it was in light saw it as blue and black. (It was actually a blue and black dress, in light. But the photo was taken in such a way that most people thought it was in shadow.)

[smeej]

This one drives me crazy because even having seen a picture of the same blue and black dress in direct light, my brain simply will not see this as anything but white and gold. I know I'm seeing it wrong and still can't see it right.

[phatskat]

Mine has changed over the years - usually I see blue and black, but occasionally I see white and gold.