Friday, July 09, 2010

The reading module of our brains.

I’ve been meaning to mention an excellent article by Oliver Sachs in the June 28 issue of The New Yorker “A man of letters”. It describes a class of stroke patients who selectively loose the ability to read letters, frequently seeing them as some kind of foreign gibberish, yet can still write (“alexia sine agraphia”). In this article, unlike some of his others which have frustrated me by not getting down to the brain basics, he give an excellent summary of how it is that our brains come to have a specialized module for a skilled activity that was invented only ~5,000 years ago, less than an eye blink in evolutionary time. Here is my editing of chunks that give the bottom line:
There may be objects that are recognized at birth, such as faces, but beyond this the world of objects must be learned through experience and activity: looking, touching, handling, correlating the feel of objects with their appearance...Visual object recognition depends on the inferotemporal cortex..where neuronal function is very plastic...Mark Changizi and colleagues at Caltech, from examining more than a hundred ancient and modern writing systems, have shown that all of them, while geometrically very different, share certain basic topological similarities...which resemble topological invariants in a range of natural settings, leading them to hypothesize that the shapes of letters "have been selected to resemble the conglomeration of contours found in natural scenes, thereby tapping into our already-existing object recognition mechanisms."

The origin of writing and reading cannot be understood as a direct evolutionary adaptation. It is dependent on the plasticity of the brain, and on the fact that, even within the small span of a human lifetime, experience - experiential selection - is as powerful an agent of change as natural selection... We are literate not by virtue of a divine intervention (which Alfred Russel Wallace proposed, contra Darwin) but through a cultural invention and a cultural selection that make a brilliant and creative new use of a preexisting neural proclivity.

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