There's no greater illusion than the way the mind links visual input to tactile sensation... Humans really believe that a cube could never feel exactly like a sphere when touching it. It's almost impossible to imagine running your finger over the corner of a cube and feeling it as smooth as a bowling ball and undifferentiated from the rest of the cube. We can barely comprehend how touching a pointy edge could not feel like a pointy edge.

This link is entirely illusory and created by the brain. There is no TRUE link between the two. Only learned or instinctual.