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Comment by bschne | Hacker News Reader

> Problem #1: What about all the other features?

Is this necessarily a problem in the argument? If we consider e.g. color, and construct a blurry image that has a color distribution very similar to a real face, but doesn't fire the edge detection in the same way, we can still recognize it as a face. This could just mean that a sufficiently close match to other examples of the same class on any one of the strong "dimensions" of the image our brain processes is sufficient to make us recognize it, no? The author makes it sound like if edge detection is what makes us recognize line drawings, this implies that our brain discards every other feature in attempts to recognize visual input, but I don't think that's a sound conclusion.

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The "Problem #2" that they mention also has an easy solution.

If the "intermediate" variable / internal representation is just "the input image but with edges only," then of course you can see internal representations.

When you compute that intermediate variable for the line drawing, it will just happen to behave like the identity function for that particular case. So if you have already filtered out non-edges then the transformation is basically a no-op.

The "types" mismatching as they mention is not a concern because the type is just "image" i.e. a big vector of HSL values or something. Edge detection is just a convolution filter so it's going to have approximately the same type as the input.

This stood out to me as well. If I close my eyes and walk into a wall I will still perceive the wall.

Our various senses help build an understanding of what's going on. It's not like we fail to understand anything once you remove one part of the system.

Maybe this person is trying to say something deeper or more nuanced and I fail to understand the meaning behind it.

Yes that stuck out to me as well. The author seems to be setting up a straw man, as if people are arguing that the brain can't distinguish between a line drawing and the real thing (or a line drawing and a photograph).

The other information isn't necessarily discarded. It's just used to identify that this is a line drawing and not the real thing. It's still remarkable that just the lines themselves (I make no claim as to whether it really is edge detection or something else) are still enough information to be able to identify the representation, but it doesn't mean the brain is discarding the other information.

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