David Smith tweeted: “Mind = blown. These two blocks are exactly the same shade of grey. Hold your finger over the seam and check.”

I’d like to do some more thinking on perceptual illusions. I don’t think that the grays look different due to any conceptual inference. The grays look very different, until the seam is covered, and then they look the same.

Yet I don’t think that these are “perceptual errors.” Rather, this is exactly how our perceptual system is supposed to work, perhaps because such mechanisms enable us to properly judge shades and depth in the real world. However, particular with computer images, we can reveal these oddities and limits in our perceptual systems in a stark way.

Notably, these kinds of cases are very different from many traditional illusions like a stick bent in water, which are a function of the medium of perception (i.e. air versus water). Still, I don’t think that they reveal that our senses aren’t reliable or valid: they just reveal, in yet another stark way, that the diaphanous model of perception is wrong.

Thoughts?