Neurobiological aspects of reading

Verbatim from Alan Jacobs’ The Pleasures of Reading in the Age of Distraction (Oxford UP, 2011; 27-28):

The tale of reading,’ Dehaene writes, ‘begins when the retina receives photons reflected off the written page. But the retina is not a homogenous sensor. Only its central part, called the fovea, is dense in high-resolution cells sensitive to oncoming light, while the rest of the retina has a coarser resolution. The fovea, which occupies about 15 degrees of the visual field, is the only part of the retina that is genuinely useful for reading.’ This limited field of high-resolution sensing means that our eyes have to travel across a page in a series of zig-zag movements called saccades, which, once we have become experienced readers, allow us to identify words even when we just discern some of the letters in them, and sentences even when we can only truly see a couple of words at a time. We are, however, usually aware in a general way of a dozen or so letters ahead of the one we’re focused on at any given time, and about 10 percent of the time our eyes are darting back over words we’ve already read to make sure we got them right. This rather complicated optical dance–or rather, the limited sensorial equipment that mandates the dance–places a pretty firm limit on our maximum reading speed. Fluent readers achieve about five hundred words a minute, and that’s not far from the best we can do, given the limited focal abilities our retinas possess.

Our brains, however, can process words much faster than our eyes can and are extremely skilled at filtering out noise and discerning signals.

The almost frictionless processing of this information takes place mostly in a particular region of the brain: Dehaene says we can find it ‘on the edge of the left occipito-temporal fissure’…

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