sharply discerns only a small portion of the field of view. A series of eye jerks constructs a composite, high-resolution image of the interesting portion of the visual field.
Consciousness and memory do not record or notice each jerky ‘exposure’. Indeed, if we were to make a motion picture that jumped around the way the eye does, the product would be nervewracking or nauseating. Our vision does not bother us as this movie would, because attention controls the focus target; attention does not passively follow the jumps.
A closer analogy to functioning of the eye and mind is the photomosaic, a composite image formed by superimposing the best parts of many overlapping images. To make a photomosaic of a region from satellite photographs, analysts do not simply paste overlapping images. They pick the best photo for each region, discarding the photos taken during night or through clouds. Perhaps the eye/mind pair acts somewhat similarly; from an airplane it can put together an image of the landscape, even through scattered small clouds. Furthermore, it can see even with stroboscopic light. Both motion pictures and fluorescent light are stroboscopic; we do not even notice because of the high frequency of flashes.
Julian Hochberg suggested a simple exercise that offers insight into the relationship of vision to memory: remember how many windows are on the front of your house or apartment house [Neisser, 1968]. You may be able to solve this problem ‘analytically’, by listing the rooms visible from the front and remembering how many windows face front in each room. Instead, you probably will use more obvious visualization, creating a mental image of the front of your house, and then scanning this image while counting windows. This mental image does not correspond to any single picture that the eye has ever seen. There may be no single location outside your house where you could stand and count every window; trees or bushes probably hide some windows.
During the last thousand years, various cultures have grappled with the discrepancy between construct and reality, or that between perspective and reality. More than six centuries before Descartes’ experiment with the eye of an ox, Arab scientists were making discoveries in optics. Alhazen, who wrote Optics [~1000 A.D.], realized that vision consists of light reflecting off of objects and forming a cone of light entering the eye. This first step toward an understanding of perspective was ignored by western scientists and artists. Artists tried to paint scenes as they are rather than as they appear to the eye. Beginning in the 15th century and continuing into the 16th century, artists such as Filippo Brunelleschi began to deliberately use Arab and Greek theories of perspective to make paintings appear more lifelike.
The perspective painting is lifelike in its mimicry of the way an eye or camera sees. In contrast, the older attempts to paint objects ‘as they are’ are more analogous to mental schemata. In this sense, the evolution of physics has paralleled that of art. Newton described dynamics as a picture of ‘how things are’, rather than how they appear to the observer. In contrast, Einstein demonstrated that we can only know things from some observer’s perspective.
The electrical activity in the brain is not designed to store a photograph in a certain location, the way that one can electrically (or magnetically) store a scanned image in a computer. True, visual imaging is generally located in one part of the brain called the visual cortex, but removal of any small part of the brain does not remove individual memories and leave all others unchanged; it may weaken certain types of memories. Memories are much more complex than mental images. They may include visual, auditory, and other sensual data along with emotional information. Recollection involves their simultaneous retrieval from different parts of the brain. A memory consists of mental electrical activity, more analogous to countless conductors in parallel than to a scanned image. However, this analogy offers little or no real insight into how the mind/brain works.
