Inside the Letterbox: How Literacy Transforms the...

June 16, 2013

$Inside the Letterbox: How Literacy Transforms the Human Brain Although I find the diversity of the world’s writing systems bewildering, there is also a striking regularity that remains hidden. Whenever we read—whether our language is Japanese, Hebrew, English, or Italian—each of us relies on very similar brain networks. In particular, a small region of the visual cortex becomes active with remarkable reproducibility in the brains of all readers. A brief localizer scan, during which images of brain activity are collected as a person responds to written words, faces, objects, and other visual stimuli, serves to identify this region. Written words never fail to activate a small region at the base of the left hemisphere, always at the same place, give or take a few millimeters. Experts call this region the visual word form area, but in a recent book for the general public, I dubbed it the brain’s letterbox, because it concentrates much of our visual knowledge of letters and their configurations. Indeed, this site is amazingly specialized. The letterbox responds to written words more than it does to most other categories of visual stimuli, including pictures of faces, objects, houses, and even Arabic numerals.Its efficiency is so great that it even responds to words that we fail to recognize consciously—words made subliminal by flashing them for a fraction of a second. Yet it performs highly sophisticated operations that are indispensable to fluent reading. For instance, the letterbox is the first visual area that recognizes that “READ” and “read” depict the same word by representing strings of letters invariantly for changes in case, which is no small feat if you consider that uppercase and lowercase letters such as “A” and “a” bear very little similarity. Furthermore, if it is impaired or disconnected via brain surgery or a cerebral infarct (type of stroke), the patient may develop a syndrome called pure alexia. He or she will be unable to recognize even a single word, as well as faces, objects, digits, and Arabic numerals. Yet many of these patients can still speak and understand spoken language fluently, and they may even still write; only their visual capacity to process letter strings seems dramatically affected. The brain of any educated adult contains a circuit specialized for reading. But how is this possible, given that reading is an extremely recent and highly variable cultural activity? The alphabet is only about 4,000 years old, and until recently, only a very small fraction of humanity could read. Thus, there was no time for Darwinian evolution to shape our genome and adapt our brain networks to the particularities of reading. How is it, then, that we all possess a specialized letterbox area? Read more$

Inside the Letterbox: How Literacy Transforms the Human Brain

Although I find the diversity of the world’s writing systems bewildering, there is also a striking regularity that remains hidden. Whenever we read—whether our language is Japanese, Hebrew, English, or Italian—each of us relies on very similar brain networks. In particular, a small region of the visual cortex becomes active with remarkable reproducibility in the brains of all readers. A brief localizer scan, during which images of brain activity are collected as a person responds to written words, faces, objects, and other visual stimuli, serves to identify this region. Written words never fail to activate a small region at the base of the left hemisphere, always at the same place, give or take a few millimeters.

Experts call this region the visual word form area, but in a recent book for the general public, I dubbed it the brain’s letterbox, because it concentrates much of our visual knowledge of letters and their configurations. Indeed, this site is amazingly specialized. The letterbox responds to written words more than it does to most other categories of visual stimuli, including pictures of faces, objects, houses, and even Arabic numerals.Its efficiency is so great that it even responds to words that we fail to recognize consciously—words made subliminal by flashing them for a fraction of a second. Yet it performs highly sophisticated operations that are indispensable to fluent reading. For instance, the letterbox is the first visual area that recognizes that “READ” and “read” depict the same word by representing strings of letters invariantly for changes in case, which is no small feat if you consider that uppercase and lowercase letters such as “A” and “a” bear very little similarity. Furthermore, if it is impaired or disconnected via brain surgery or a cerebral infarct (type of stroke), the patient may develop a syndrome called pure alexia. He or she will be unable to recognize even a single word, as well as faces, objects, digits, and Arabic numerals. Yet many of these patients can still speak and understand spoken language fluently, and they may even still write; only their visual capacity to process letter strings seems dramatically affected.

The brain of any educated adult contains a circuit specialized for reading. But how is this possible, given that reading is an extremely recent and highly variable cultural activity? The alphabet is only about 4,000 years old, and until recently, only a very small fraction of humanity could read. Thus, there was no time for Darwinian evolution to shape our genome and adapt our brain networks to the particularities of reading. How is it, then, that we all possess a specialized letterbox area?