A fascinating exploration of sight, and how compartmentalized the process is in our brains. Inside each of us, the task we think of holistically as "seeing" the world is divided up among over 30 different areas of the brain, including an area that senses all motion, an area that senses all edges, an area that recognizes only faces, and areas that selectively filter our environment and guide our eyes to find the relevant details of a scene. Near the end, professor Rudolfo Llinas states his theory that the majority of our visual process is closely related to dreaming. Since the myriad visual sections of the brain have just as much information flowing into them as out of them, we actually walk around constructing a mental image of what we should be seeing, based on past experience, and comparing it with what our eyes tell us in the present. We do this in an immediate sense to recognize objects, then again to figure out where we are, and as an ongoing process to keep track of what's relevant around us - what needs attention.
Visualize it as a loop of magnetic tape, strung between two reels inside your brain, and your eyes are reading from and writing to one point simultaneously as the tape loops around and around.
I think all us "introspective" people can relate to this idea.