This is interesting and really counterintuitive for me after seeing the results.
I would assume (and still can't shake the feeling) that a blind person would clearly know that a cube/square has corners and a sphere/circle does not. It's hard to understand how that isn't obvious when seeing for the first time. Even if it wasn't immediately understood, one should be able to trace, with fingers or eyes or whatever else, the outline of a cube vs sphere and observe that only one has corners. The act of tracing should match the tactile sensation of moving your fingers around similar objects.
I think it is a mistake to think that what we "see" comes from our eyes rather than from a large, trained visual network in the brain. Consider, for instance, the behavior of the eye's blind spot, or the fact that we perceive objects in one plane of vision despite having two eyes. These effects can't come from just raw data.
Someone who hasn't learned/trained that processing is probably going to see something much more strange--do you think you would be able to differentiate between a sphere and a square by looking at hexdumps of bitmap files?
I would assume (and still can't shake the feeling) that a blind person would clearly know that a cube/square has corners and a sphere/circle does not. It's hard to understand how that isn't obvious when seeing for the first time. Even if it wasn't immediately understood, one should be able to trace, with fingers or eyes or whatever else, the outline of a cube vs sphere and observe that only one has corners. The act of tracing should match the tactile sensation of moving your fingers around similar objects.