In an interesting experiment at the University of Arizona, researchers have found that your brain does a lot of processing of visual information, and sees things that your conscious self doesn’t “see”.
When looking at the famous image of a vase that has faces on either side, your bring is doing processing of the negative images in white. They hooked subjects up to an EEG, the researches looked at the brainwaves of the subjects when they were exposed to images of black middle figures (silhouettes) with negative white space on either side, similar to the faces and vase picture. There is an N400 spike when looking at images where there is something in the negative white. That means that 400 ms after the image is shown, the brain shows a negative voltage spike. But it only does this when there is something in the negative white. There is no N400 spike if it’s just a center black object and the sides don’t mean anything.
So the brain is processing the white shapes, but not necessarily passing that on to the consciousness. There are things that your brain senses, but you don’t perceive.
Oliver Sacks had an interesting case study about something similar — a woman who was blind as far as her consciousness was concerned. However, when given tests like “put this envelope in a mail slot that’s somewhere on this wall”, she could correctly find the slot (without, say, touching the wall.)
It was one of the ones in The Man Who Mistook His Wife for a Hat, I think. Pretty cool. 🙂