Written language is processed in about a dozen different brain areas (and principally in the left hemisphere in most people). Written language must be explicitly taught, and is more difficult to master than speech, which children effortlessly master with limited explicit instruction. For example, when did you teach your children prepositional phrases or how to form plurals?

One explanation for the greater difficulty of learning to read and write is that written language is only a few thousand years old, not enough time for innate systems for processing reading/writing to evolve. The neuroscientist Stanislas Dehaene (2003) suggests that the reason we can learn to read and write is that written language makes use of visual recognition capabilities that are innate. The basic brain structures we use to recognize words also exist in the visual systems of primates, where they are used to recognize important objects—dangers and opportunities.

For example, a monkey must be able to quickly recognize a lion. Although each lion is slightly different from other lions, all have a characteristic lion face, and it is that configuration (a sort of cartoon lion with only the essential details) that the monkey's object recognition system tunes into. Further, the lion might be looking up/down/sideways/etc., so the object recognition system must be able to recognize the conceptual lion in any possible positional variation.

Nature contains many basic recurring shapes such as ovals and triangles that combine to form more complex objects such as a face. To natural object forms such as trees and stones that we instantly recognize regardless of the variations, we humans have added many cultural icons—such as a Nike swoosh, a McDonald's arch, and various traffic symbols. All contain only the minimum amount of information needed for rapid recognition (a phenomenon that cartoonists also exploit in their work).

Dehaene argues with considerable research support that we simply adapted this existing innate object recognition system to written language when it entered into human culture. For example, draw a capital A with the horizontal line extending a bit beyond the two diagonal lines, and place a couple dots above the horizontal line within the triangle. Invert the drawing and it's a cartoon bull. Our letter A derives from the Greek alpha, which emerged out of the ancient Semitic word for bull (alf). As suggested above our brain has no difficulty in recognizing a shape such as A whether it's right side up, upside down, or sideways.