Mind Reading
January 5th 2010 20:32
Signature Tune
By ALISON GOPNIK
neurons
At this very moment, you are actually moving your eyes over a white page dotted with black marks. Yet you feel that you are simply lost in the universe of The New York Times Book Review, alert to the seductive perfume of a promising new novel and the acrid bite of a vicious critical attack. That transformation from arbitrary marks to vivid experience is one of the great mysteries of the human mind. It’s especially mysterious because reading is a relatively recent invention, dating to some 5,000 to 10,000 years ago. Our brains didn’t evolve to read.
Brain path
READING IN THE BRAIN
The Science and Evolution of a Human Invention
By Stanislas Dehaene
Illustrated. 388 pp. Viking. $27.95
Stanislas Dehaene, a distinguished French cognitive scientist, has helped unravel that mystery. His gifts, on display in “Reading in the Brain,” include an aptitude for complex experiments and an appetite for detail. This makes for excellent science but not, paradoxically, easy reading. Still, his book will repay careful study, even if it doesn’t inspire blissful absorption.
Dehaene begins by describing the remarkably complicated neural circuitry devoted to getting from marks to thoughts. He then explains how reading developed historically (from Sumerian inscriptions and Egyptian hieroglyphics to the Greek and Roman alphabets and Chinese characters), how we learn to read as children and why dyslexia makes reading so hard.
Every time you complete a word recognition security test on a Web site, you are paying unconscious homage to the sophistication and subtlety of the reading brain. The most advanced spambots can’t even recognize letters as well as we can, let alone recover the meaning that lurks behind them. Cognitive science has shown that the simplest experiences — talking, seeing, remembering — are the result of fiendishly complex computations. Dehaene’s work, along with that of others, adds reading to the list.
But Dehaene also makes an argument that goes beyond reading, an argument about human nature itself. In “Reading in the Brain,” he adopts the rhetoric of innateness, a complex of ideas developed by Noam Chomsky 50 years ago and popularized by evolutionary psychologists like Steven Pinker. He argues that reading is highly constrained by fixed, innate brain structures with only a little flexibility, just enough to allow this unprecedented skill to emerge at all.
But there are two very different kinds of innateness. Chomsky proposed that we are born with specific, genetically determined neural and cognitive structures, structures that go far beyond a few general learning mechanisms. This kind of innateness has become the established wisdom in cognitive science. The brain is not a blank slate.
However, the other, more significant, kind of innateness concerns not the history of the mind but its future. Chomsky also argued that innate structure places very strong constraints on the human mind. Evolutionary psychologists who echo Chomsky say we are stuck with the same brains as our hunter-gatherer ancestors, with just a little tinkering around the edges.
Many social scientists reject this second claim. A new generation of cognitive scientists and neuroscientists are starting to reject it, too. In the past few years, computer scientists have developed new machine learning techniques that allow computers to make genuinely new discoveries, and cognitive scientists have begun to discover that even young children’s minds learn in much the same way. At the same time, neuroscientists have discovered that the brain is much more plastic — more influenced by experience — than we used to think. The brain is highly structured, but it is also extremely flexible. It’s not a blank slate, but it isn’t written in stone either.
Dehaene describes some fascinating and convincing evidence for the first kind of innateness. In one of the most interesting chapters, he argues that the shapes we use to make written letters mirror the shapes that primates use to recognize objects. After all, I could use any arbitrary squiggle to encode the sound at the start of “Tree” instead of a T. But actually the shapes of written symbols are strikingly similar across many languages.
It turns out that T shapes are important to monkeys, too. When a monkey sees a T shape in the world, it is very likely to indicate the edge of an object — something the monkey can grab and maybe even eat. A particular area of its brain pays special attention to those significant shapes. Human brains use the same area to process letters. Dehaene makes a compelling case that these brain areas have been “recycled” for reading. “We did not invent most of our letter shapes,” he writes. “They lay dormant in our brains for millions of years, and were merely rediscovered when our species invented writing and the alphabet.”
However, the very fact that our brains have become so exquisitely adapted for reading looks like an argument against the second kind of innateness — the written in stone kind. Dehaene also endorses the Chomskyan view that reading is highly constrained — that “new cultural inventions can only be acquired insofar as they fit the constraints of our brain architecture” — but it’s not so clear that he really believes it himself. For example, he argues that the primate brain has evolved to treat symmetrical shapes, like the letter pairs p and q, or b and d, as if they were the same. This explains why children, and dyslexics, have so much trouble distinguishing these letters. It also explains our extraordinary ability to “mirror-read” and “mirror-write.” Many children spontaneously reverse not just single letters but whole paragraphs of text.
Alison Gopnik is the author of “The Philosophical Baby: What Children’s Minds Tell Us About Truth, Love, and the Meaning of Life.”
From: The New York Times
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