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Amazement awaits us at every corner.
—James Broughton, American poet and filmmaker (1913–1999)
To people, the world looks richly complete in all details, like a film. The information transmitted by the retina to the brain is constrained by physical limitations, however, such as the relatively small number of nerve fibers in the optic nerve. One way our visual system overcomes these limitations—thus presenting us with the perception of a fully realized world—is by disregarding redundant features in objects and scenes, thereby extracting, emphasizing and processing only the unique components that are critical to describing an object. Next time you visit the Guggenheim Museum in New York City and see a white canvas hanging on the wall, realize that what you perceive—a rectangular field of white—and what your eyes send to your brain—information about where the canvas's edges meet the wall behind the painting—are not equivalent.
As American vision scientist Fred Attneave proposed in the 1950s, just as edges inform the viewer more than uniform fields of color, “points of maximum curvature,” or discontinuities in edges, such as curves, angles and corners, are less redundant and thus contain more information than the edges themselves. British neuroscientist Horace Barlow proposed in the 1960s that the brain throws out some information, but little of what is important about the visual world is lost. This idea, known as the redundancy-reducing hypothesis, may explain why neurons at the early stages of visual processing respond more intensively to the edges of objects than to interiors. Redundancy reduction applies to other visual features as well, such as the edges of edges: curves and corners.