WEB TEXT: The Science of Sight

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Science  14 May 2004:
Vol. 304, Issue 5673, pp. 935
DOI: 10.1126/science.304.5673.935a

Do you see faint blobs where the white “avenues” cross in the diagram? You're not losing your eyesight; you've simply fallen for the Hermann grid illusion, one of the tricks that help researchers deduce the workings of the visual system. For a clear view of how we see, check out The Joy of Visual Perception, an undergraduate-level Web text by professor emeritus of psychology Peter Kaiser of York University in Toronto, Canada. Students can start by focusing on physiology and anatomy, including the structure of the eye and the transmission of messages across the gaps between neurons. Other sections let us peer into subjects such as how we perceive contrast, size, motion, and distance.

The text also reveals the secrets behind a long list of fun and instructive illusions. The shadows on the Hermann grid, for instance, result from the arrangement of inhibitory and excitatory receptors in the retina.


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