In 2009, French cognitive neuroscientist Stanislas Dehaene proposed in his book Reading in the Brain a hypothesis to describe brain activity in humans when they read. He calls it neuronal recycling, and it’s based on a few elementary facts.
Writing systems and reading have been around for only about 5,000 years, much too short a timeframe for humans to evolve brain structures tailored specifically to reading. So, obviously, humans did not evolve reading as a skill. Dehaene’s thesis is based on MRIs of peoples’ brains while they read, and research into the anatomy of primate brains. In chimpanzee and macaque brain structures, neurologists have learned that synapses within the occipital and inferior temporal areas fire when the subject is shown certain shapes.
Dehaene has also found the analagous areas in human brains in use while a person is reading. In simple terms, the author’s hypothesis states that reading “hijacks” these brain structures evolved to recognize certain critical shapes and directed their use to recognizing letters and words. From there, writing systems have adapted to take advantage of some apparently pre-programmed, or evolved, primate brain functions. The result is a literate population who can communicate in great detail with the dead, and can leave communications for future generations after they themselves are dead. It’s obviously a superpower.
A survey of writing systems through the last few thousand years revealed some intriguing parallels. For instance, most characters are composed of roughly three strokes that can be traced without ever lifting or stopping the pen or stylus. Dehaene proposes that this formula corresponds to the way the neurons’ react to increasing complexity of the symbols. In all writing systems across the world, characters appear to have evolved to an almost optimal combination that can easily be grasped the multi-tiered way the brain works as we read. At lower levels of our visual comprehending system, the strokes themselves consist of two, three or four line segments. At one level up, in our alphabetical systems, multiletter units such as word roots, prefixes, suffixes, and grammatical endings are almost invariably two, three, or four letters long. In Chinese, most characters consist in a combination of two, three, or four semantic and phonetic subunits. Visually speaking, all writing systems seem to rely on a pyramid of shapes whose golden section is the number 3 plus or minus 1.
I confess there are chapters in this book I did not read. They were very technical, written for other neuroscientists, covering dyslexia and the implications for the teaching of reading. The level of detail here is deep and comprehensive. The style is straightforward and clear, comprehensible to any adult reader. I did get the diverting feeling as I read, as I’m sure Dehaene did while writing, that readers of his book had to engage in this marvelous, unique skill, while learning about the marvelous, unique skill they were using. Quite enjoyable.
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