PENGUIN BOOKS
READING IN THE BRAIN
French scientist Stanislas Dehaene was trained as a mathematician and psychologist before becoming one of the world’s most active researchers on the cognitive neuroscience of language and number processing in the human brain. He is the director of the Cognitive Neuroimaging Unit in Saclay, France; professor of experimental cognitive psychology at the Collège de France; and a member of both the French Academy of Sciences and the pontifical Academy of Sciences. He has published extensively in peer-reviewed scientific journals and is the author of several books, including The Number Sense.
Praise for Reading in the Brain
A Washington Post Best Science Book of 2009
A Library Journal Best Sci-Tech Book of 2009
“In his splendid Reading in the Brain, French neuroscientist Stanislas Dehaene reveals how decades of low-tech experiments and high-tech brain-imaging studies have unwrapped the mystery of reading and revealed its component parts. . . . A pleasure to read. [Dehaene] never oversimplifies; he takes the time to tell the whole story, and he tells it in a literate way.”
—The Wall Street Journal
“Fascinating . . . By studying the wet stuff inside our head, we can begin to understand why this sentence has this structure, and why this letter, this one right here, has its shape. . . . Eloquent . . . Provide[s] a wealth of evidence.”
—Jonah Lehrer
“Dehaene’s masterful book is a delight to read and scientifically precise.”
—Nature
“Combining research and narrative, Dehaene weaves a fascinating explanation of how the prefrontal cortex co-opted primeval neurological pathways to learn a uniquely human skill.”
—Seed
“The transparent and automatic feat of reading comprehension disguises an intricate biological effort, ably analyzed in this fascinating study. . . . This lively, lucid treatise proves once again that Dehaene is one of our most gifted expositors of science; he makes the workings of the mind less mysterious, but no less miraculous.”
—Publishers Weekly
“Richly rewarding.”
—Kirkus Reviews
“[Dehaene] is that rare bird: a scientist who can write.”
—The Globe and Mail (Toronto)
“Inspire[s] a sense of wonder at the complexity at the task readers are performing just by scanning from page to page.”
—A.V. Club.com
“We are fortunate that Stanislas Dehaene, the leading authority on the neuro-science of language, is also a beautiful writer. His Reading in the Brain brings together the cognitive, the cultural, and the neurological in an elegant, compelling narrative. It is a revelatory work.”
—Oliver Sacks, M.D.
“In a moment when knowledge about the reading brain may be the key to its preservation, Stanislas Dehaene’s book provides the next critical rung of that knowledge. He does this through insights gained from his own prolific research, through his comprehensive grasp of the neurosciences, and through his unique combination of common sense and wisdom that shines through every chapter.”
—Maryanne Wolf, author of Proust and the Squid: The Story and Science of the Reading Brain
“Stanislas Dehaene takes us on a journey into the science of reading. We travel past firing neurons in monkeys, brain activation patterns in humans, people with brain damage, and culture as a whole. It’s a proactive and enjoyable synthesis of a tremendous amount of information, with just the right balance between getting the facts right and making them accessible to lay readers.”
—Joseph LeDoux, University Professor, New York University, and author of Synaptic Self and The Emotional Brain
“Reading in the Brain isn’t just about reading. It comes nearer than anything I have encountered to explaining how humans think, and does so with a simple elegance that can be grasped by scientists and nonscientists alike. Dehaene provides insight about the neurological underpinnings of the spectacular cognitive skills that characterize our species. Students of human evolution are not the only ones who will find Reading in the Brain fascinating. Parents, educators, and anyone else who nurtures the intellectual development of children cannot afford to ignore Dehaene’s observations about the best methods for teaching them to read!”
—Dean Falk, author of Finding Our Tongues: Mothers, Infants, and the Origins of Language
“The complicated partnership of eye and mind that transforms printed symbols into sound, music, and meaning, and gives rise to thought, is the subject of this intriguing study. It’s a wondrous journey: like that of stout Cortez, like H. M. Stanley’s search for Dr. David Livingstone, like the next stunning probe into outer space.”
—Howard Engel, coauthor of The Man Who Forgot How to Read
Reading in the Brain
The New Science
of How We Read
STANISLAS DEHAENE
INTRODUCTION
The New Science of Reading
Withdrawn into the peace of this desert, along with some books, few but wise, I live in conversation with the deceased, and listen to the dead with my eyes
—FRANCISCO DE QUEVEDO
At this very moment, your brain is accomplishing an amazing feat—reading. Your eyes scan the page in short spasmodic movements. Four or five times per second, your gaze stops just long enough to recognize one or two words. You are, of course, unaware of this jerky intake of information. Only the sounds and meanings of the words reach your conscious mind. But how can a few black marks on white paper projected onto your retina evoke an entire universe, as Vladimir Nabokov does in the opening lines of Lolita:
Lolita, light of my life, fire of my loins. My sin, my soul. Lo-lee-ta: the tip of the tongue taking a trip of three steps down the palate to tap, at three, on the teeth. Lo. Lee. Ta.
The reader’s brain contains a complicated set of mechanisms admirably attuned to reading. For a great many centuries, this talent remained a mystery. Today, the brain’s black box is cracked open and a true science of reading is coming into being. Advances in psychology and neuroscience over the last twenty years have begun to unravel the principles underlying the brain’s reading circuits. Modern brain imaging methods now reveal, in just a matter of minutes, the brain areas that activate when we decipher written words. Scientists can track a printed word as it progresses from the retina through a chain of processing stages, each of which is marked by an elementary question: Are these letters? What do they look like? Are they a word? What does it sound like? How is it pronounced? What does it mean?
On this empirical ground, a theory of reading is materializing. It postulates that the brain circuitry inherited from our primate evolution can be co-opted to the task of recognizing printed words. According to this approach, our neuronal networks are literally “recycled” for reading. The insight into how literacy changes the brain is profoundly transforming our vision of education and learning disabilities. New remediation programs are being conceived that should, in time, cope with the debilitating incapacity to decipher words known as dyslexia.
My purpose in this book is to share my knowledge of recent and little-known advances in the science of reading. In the twenty-first century, the average person still has a better idea of how a car works than of the inner functioning of his own brain—a curious and shocking state of affairs. Decision makers in our education systems swing back and forth with the changing winds of pedagogical reform, often blatantly ignoring how the brain actually learns to read. Parents, educators, and politicians often recognize that there is a gap between educational programs and the most up-to-date findings in neuroscience. But too frequently their idea of how this field can contribute to advances in education is only grounded in a few color pictures of the brain at work. Unfortunately, the imaging techniques that allow us to visualize brain activity are subtle and occasionally misleading. The new science of reading is so young and fast-moving that it is still relatively unknown outside the scientific community. My goal is to provide a simple introduction to this exciting field, and to increase awareness of the amazing capacities of our reading brains.
From Neurons to Education
Reading acquisition is a major step in child development. Many children initially struggle with reading, and surveys indicate that about one adult in ten fails to master even the rudiments of text comprehension. Years of hard work are needed before the clockwork-like brain machinery that supports reading runs so smoothly that we forget it exists.
Why is reading so difficult to master? What profound alterations in brain circuitry accompany the acquisition of reading? Are some teaching strategies better adapted to the child’s brain than others? What scientific reasons, if any, explain why phonics—the systematic teaching of letter-to-sound correspondences—seems to work better than whole-word teaching? Although much still remains to be discovered, the new science of reading is now providing increasingly precise answers to all these questions. In particular, it underlines why early research on reading erroneously supported the whole-word approach—and how recent research on the brain’s reading networks proves it was wrong.
Understanding what goes into reading also sheds light on its pathologies. In our explorations of the reader’s mind and brain, you will be introduced to patients who suddenly lost the ability to read following a stroke. I will also analyze the causes of dyslexia, whose cerebral underpinnings are gradually coming to light. It is now clear that the dyslexic brain is subtly different from the brain of a normal reader. Several dyslexia susceptibility genes have been identified. But this is by no means a reason for discouragement or resignation. New intervention therapies are now being defined. Intensive retraining of language and reading circuits has brought about major improvements in children’s brains that can readily be tracked with brain imaging.
Putting Neurons into Culture
Our ability to read brings us face-to-face with the singularity of the human brain. Why is Homo sapiens the only species that actively teaches itself? Why is he unique in his ability to transmit a sophisticated culture? How does the biological world of synapses and neurons relate to the universe of human cultural inventions? Reading, but also writing, mathematics, art, religion, agriculture, and city life have dramatically increased the native capacities of our primate brains. Our species alone rises above its biological condition, creates an artificial cultural environment for itself, and teaches itself new skills like reading. This uniquely human competence is puzzling and calls for a theoretical explanation.
One of the basic techniques in the neurobiologist’s toolkit consists of “putting neurons in culture”—letting neurons grow in a petri dish. In this book, I call for a different “culture of neurons”—a new way of looking at human cultural activities, based on our understanding of how they map onto the brain networks that support them. Neuroscience’s avowed goal is to describe how the elementary components of the nervous system lead to the behavioral regularities that can be observed in children and adults (including advanced cognitive skills). Reading provides one of the most appropriate test beds for this “neurocultural” approach. We are increasingly aware of how writing systems as different as Chinese, Hebrew, or English get inscribed in our brain circuits. In the case of reading, we can clearly draw direct links between our native neuronal architecture and our acquired cultural abilities—but the hope is that this neuroscience approach will extend to other major domains of human cultural expression.
The Mystery of the Reading Ape
If we are to reconsider the relation between brain and culture, we must address an enigma, which I call the reading paradox: Why does our primate brain read? Why does it have an inclination for reading although this cultural activity was invented only a few thousand years ago?
There are good reasons why this deceptively simple question deserves to be called a paradox. We have discovered that the literate brain contains specialized cortical mechanisms that are exquisitely attuned to the recognition of written words. Even more surprisingly, the same mechanisms, in all humans, are systematically housed in identical brain regions, as though there were a cerebral organ for reading.
But writing was born only fifty-four hundred years ago in the Fertile Crescent, and the alphabet itself is only thirty-eight hundred years old. These time spans are a mere trifle in evolutionary terms. Evolution thus did not have the time to develop specialized reading circuits in Homo sapiens. Our brain is built on the genetic blueprint that allowed our hunter-gatherer ancestors to survive. We take delight in reading Nabokov and Shakespeare using a primate brain originally designed for life in the African savanna. Nothing in our evolution could have prepared us to absorb language through vision. Yet brain imaging demonstrates that the adult brain contains fixed circuitry exquisitely attuned to reading.
The reading paradox is reminiscent of the Reverend William Paley’s parable aimed at proving the existence of God. In his Natural Theology (1802), he imagined that in a deserted heath, a watch was found on the ground, complete with its intricate inner workings clearly designed to measure time. Wouldn’t it provide, he argued, clear proof that there is an intelligent clockmaker, a designer who purposely created the watch? Similarly, Paley maintained that the intricate devices that we find in living organisms, such as the astonishing mechanisms of the eye, prove that nature is the work of a divine watchmaker.
Charles Darwin famously refuted Paley by showing how blind natural selection can produce highly organized structures. Even if biological organisms at first glance seem designed for a specific purpose, closer examination reveals that their organization falls short of the perfection that one would expect from an omnipotent architect. All sorts of imperfections attest that evolution is not guided by an intelligent creator, but follows random paths in the struggle for survival. In the retina, for example, blood vessels and nerve cables are situated in front of the photoreceptors, thus partially blocking incoming light and creating a blind spot—very poor design indeed.
Following in Darwin’s footsteps, Stephen Jay Gould provided many examples of the imperfect outcome of natural selection, including the panda’s thumb.1 The British evolutionist Richard Dawkins also explained how the delicate mechanisms of the eye or of the wing could only have emerged through natural selection or are the work of a “blind watchmaker.”2 Darwin’s evolu...
