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HOME > PAST ISSUE > May-June 2002 > Article Detail

FEATURE ARTICLE

Why We See What We Do

A probabilistic strategy based on past experience explains the remarkable difference between what we see and physical reality

R. Beau Lotto, Dale Purves, Surajit Nundy

Figure 2. Several features of light determine what we see . . .Click to Enlarge Image

The visual information that reaches the eye cannot uniquely describe the physical world. Because light arising from different physical objects can stimulate the retina in the same way, the source of a light stimulus is inevitably ambiguous. For example, a large object far away and a small one closer by can generate exactly the same retinal image. The visual port of the brain resolves this ambiguity by assigning appropriate values of brightness, color and geometry to the things we see. Purves, Lotto and Nundy argue that this assignment is made on a wholly probabilistic basis: What observers see in any circumstance is simply what the stimulus has typically signified in the past, indicated by behavioral success or failure.


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