Reading in the Brain: The Science and Evolution of a Human Invention
By Stanislas Dehaene
Viking, 388 pp.
$27.95

Having tackled math in the brain with The Number Sense, Stanislas Dehaene takes on letters with his new book Reading in the Brain. Math is easily seen as an abstract and artificial exercise, but reading, as it turns out, is no more natural. While high school algebra teachers have to teach the absurdity of x and y representing unknown numbers, first grade teachers have the equally unenviable task of teaching x and y as letters. Letters are meaningless by themselves, and when they are strung together in words, you only have to add, shift, or drop one letter—any letter—to screw up the meaning. The rules seem arbitrary. “Kex” is a meaningless string but “key” is clearly something used to open a lock, even though it no more resembles a real key than “kex.”

In tracing the process of how the brain learns to read, Dehaene’s book spurs appreciation for what we, now so accustomed to reading, take for granted. The human brain is not evolved for reading, and our ability to do so may be a happy biological accident: it just so happens that the neurons for vision tenuously connect to language and sound centers in the brain. Dehaene puts forth a “neuronal recycling hypothesis,” in which the brain repurposes neurons originally adapted to other tasks. Learning to read is also a process of unlearning; our brains’ tendency to generalize mirror images explains why we have to pay special attention to mind our lowercase Ps and Qs. Evolution did not shape the reading brain, but the process of learning to read reinforces connections between visual, auditory, and language areas in each of our brains. It is no overstatement to say that reading changes the way our brains work. Learning how to spell actually makes us better at distinguishing sounds. Getting a pun or spoonerism, whose cleverness lies at the intersection of sound and spelling, is a corollary of reading.

Dehaene is professor of experimental cognitive psychology, and he does not shy away from science. Brain areas are precisely named in jargon, so be ready to acquaint yourself with the superior temporal sulcus and ventro occipito-temporal region. A map of the brain with relevant areas highlighted is the single most useful page in the book. Almost all the other images are charts and graphs reprinted from scientific papers, and Dehaene often draws from his own research. Fortunately, most of his book reads less like a Nature paper and more like a book for anyone interested in reading, both the act and the idea of it. This is all the more remarkable because French, not English, is Dehaene’s first language.

In fact, the linguistic scope of Reading in the Brain is one of its virtues. Written in English, the book is necessarily English-centric, but the most compelling examples come from juxtapositions with other languages. Italian children learn to read faster than Americans because of Italian’s highly regular spelling—evidence for the linking of auditory and visual circuits in reading. At first glance, Chinese characters seem to require a different mode of reading, but Dehaene convincingly argues that the building blocks of all written language systems have their root in universal brain circuitry. For example, certain shapes – such as a T or L-like configuration – exist in all languages because they are the ones most easily identified by our eyes. Additionally, the frequencies of these shapes in each language are constant, and they correlate with their frequencies in the natural environment.

Dehaene weaves together neuroscience and linguistics research articles with patient narratives à la Oliver Sacks. A chapter on dyslexia presents the disorder as a largely unsolved puzzle of neurodevelopment. Dyslexia was once thought to be a problem with fast visual processing, but one dyslexic patient could read normally only when the text flickered for less than one-tenth of a second. She took to reading under a strobe light. For the rest of us looking to read more quickly, consider this: the rate-limiting step of reading is not comprehension but the speed at which our eyes scan across the page. When words are presented sequentially at the eye’s focal point, reading speed can increase by a factor of four – faster than even the best speed readers. Makers of the next generation Kindles and Nooks should take note.

Although Dehaene goes into detail on how our brains parse words, he says little about how our brains parse the meanings of these words. His explanation seems unsatisfactory if we consider reading to be not only the decoding of written symbols but also the active process of reflecting on ideas articulated in them. Indeed this seems to be the definition of reading expressed in laments on modern culture like, “Nobody reads novels anymore.” The omission of this piece from Dehaene’s explanation of reading reflects not so much the limits of his book as the limits of current cognitive science research.

In the final unfurling of his argument, however, Dehaene alights on something more ambitious, what he calls a “culture of neurons.” He suggests that human culture as a whole—including science, art, religion, and as his previous book anticipated, mathematics—can be seen as a way of recycling neurons. Such pieces of culture are universal, argues Dehaene, because they tickle our underlying brain circuits. Ultimately, he would like to “understand the neuronal restrictions that define the scope of human cultural invention.” Achieving this would seem to be a paradox in human abilities: a grand accomplishment for science but a sobering resume of culture. But if anything, the evolution of reading has demonstrated that the human brain, despite its physical limits, is capable of remarkable innovation.

Sarah Zhang writes and works in a neuroscience lab in Cambridge, MA.