Friday, March 13, 2020

Reading in the Brain: The Science and Evolution of a Human Invention (Stanislas Dehaene)

Best book notes:

"We identify only ten or twelve letters per saccade: three or four to the left of fixation, and seven or eight to the right"

"whole pipeline of mental processes continues to operate for at least one-half second after the word has been presented."


"It takes only twenty or thirty milliseconds of word viewing for our brain to automatically activate a word’s spelling, but an additional forty milliseconds for its transformation into sound, as revealed by the emergence of sound-based priming"

"Visual analysis is only the first step in reading. Subsequently, a variety of distinct representations must be brought into contact: the roots of words, their meaning, their sound patterns, their motor articulation schemes. Each of these operations typically demands the simultaneous activation of several separate cortical areas whose connections are not organized in linear chains. All the brain regions operate simultaneously and in tandem, and their messages constantly crisscross each other. All the connections are also bidirectional: when a region A connects to a region B, the converse projection from B to A also exists."

"mental operation like reading"

"only one, the left occipito-temporal region, appeared to play a central and specific role in reading"

"This region is systematically located deep in the left lateral occipito-temporal sulcus"

"Reading is a cognitive, social, and cultural activity that dates back five thousand years"

"What is amazing is that in spite of these vast differences in the way we learned to read, we all call on the same area of the brain to recognize the written word."

"Quite apart from cortical topography, words and faces also have different preferred hemispheres. When we recognize a word, the left hemisphere plays the dominant role. For faces, the right hemisphere is essential."

"A good reader can recognize words regardless of how they are positioned (assuming, of course, that they do not exceed our retina’s limited resolution)."

"First, reading is a sophisticated construction game—a complex cortical assembly line is needed to progressively put together a unique neural code for each written word. Second, conscious reflection is blind to the true complexity of word recognition. Reading is not a direct and effortless process. Rather, it relies on an entire series of unconscious operations."

"Any word we read is initially funneled through the letterbox area, which plays a dominant and universal role in the recognition of writing."

"The lateral temporal region seems to play an essential role in the mediation between the shapes of words and the elements that constitute their meaning. This region can be subdivided into subregions that specialize in different categories of words. Faces, people, animals, tools, vegetables . . ."

"two essential stages in reading: the orthographic filter, which accepts legal letter strings, and the semantic filter, which sorts words according to meaning."

"Pseudo-words or meaningless strings of letters like “trid” or “plosh” that respect the spelling rules of English."

"We recognize the written word using a region that has evolved over time and whose specialty, for the past ten million years or more, has been the visual identification of objects."

"the preferred images that make the neuron fire would become increasingly complex. A small, inclined bar is enough to bring on a significant discharge in the primary visual cortex. More complex curves, shapes, fragments of objects, or even entire objects or faces are, however, needed to trigger neurons at the higher levels."

"neurons would begin to respond to increasingly broader portions of the retina. Each neuron is defined in terms of its receptive field, or the place on the retina to which it responds. The receptive fields broaden by a factor of two or three at each step. This means that the part of the retina to which the preferred object must be presented for the neuron to fire doubles or triples in diameter at each step."

"an increasing degree of invariance is present. Early on, neurons are sensitive to changes in location, size, or lighting of the incoming picture. In higher-level areas, in the move up the hierarchy, neurons tolerate increas..."

"Single neurons are slow computers. They receive and transmit information in about ten milliseconds, which is a million times slower than the speed of an electronic microprocessor."

"the Japanese neuroscientist Keiji Tanaka made a remarkable discovery: the monkey brain contains a patchwork of neurons dedicated to fragments of shape. Collectively, these primitive shapes constitute a sort of “neuronal alphabet” whose combinations can describe any complex form."

"Perhaps the most striking feature of the inferior temporal neurons is that many of their preferred shapes closely resemble our letters, symbols, or elementary Chinese characters (figures 3.4 and 3.6). Some neurons respond to two superimposed circles forming a figure eight, others react to the conjunction of two bars to form a T, and others prefer an asterisk, a circle, a J, a Y . . . For this reason, I like to call them “proto-letters.”"

"the inferior temporal cortex relies on a stock of geometrical shapes and simple mathematical invariants. We did not invent most of our letter shapes: they lay dormant in our brains for millions of years, and were merely rediscovered when our species invented writing and the alphabet."

"Complex objects are recognized through the configurations of their contours. At the places where they join, these contours form reproducible configurations shaped as T, L, Y, or F."

"the capacity to learn is the result of a sophisticated evolutionary process."

"Every child, however, in the first few months of life, quickly learns to recognize faces, voices, native language, and a sense of empathy for others"

"Neurons for Reading ... "

"neurons in the letterbox area recognize written words in less than one-fifth of a second"

"tentative model of the neuronal architecture for reading"

"A hypothetical model of the neuronal hierarchy that supports visual word recognition."

"At each stage, neurons learn to react to a conjunction of responses from the immediately lower level. At the bottom of the pyramid, which is shared by word and image recognition, neurons detect local contrasts and oriented bars. As one climbs further up, neurons become increasingly specialized for reading. They detect letters, letter pairs (bigrams), then morphemes and small words. At each stage, the receptive field broadens by a factor of two or three, while the neuronal ..."

"the well-known fact that the ventral visual system is organized as a hierarchy going from the occipital pole in the back of the brain to the anterior regions of the temporal lobe."

"At the next step, when responses from several neurons tuned to letters are combined, we arrive at neurons sensitive to letter conjunctions. Such neurons, for example, might signal the presence of the letter “N” one or two letters to the left of the letter “A”—a very useful feature if one is to separate similar strings such as “AND” and “DNA.”"

"my colleagues and I have proposed that the most useful letter combination to which neurons should attend is a “bigram”—an ordered pair of letters such as “E left of N.” It is easy to wire a neuron so that it responds selectively to this letter pair but can tolerate some shift in the location of its component letters."

"No one has ever seen bigram neurons. Their existence is the matter of an educated guess, based on what we know about the primate visual system. For the time being, they are a purely theoretical construction that cannot be tested directly with our somewhat rudimentary imaging techniques."

"Grainger and Whitney finally came up with the idea of open bigrams. They noted that words could be encoded not as a list of letters, but as a list of the pairs of letters they contained."

"This similarity explains why we can still read the word “bagde” when two of its letters are inverted."

"Another advantage of the bigram code is that it is insensitive to changes in location and size."

"bigram neurons only fire if the first letter of a pair is less than two letters away from the second."

""

"For instance, a neuron coding for the pair AM can react to the words “ham,” “arm,” and “atom,” but not to “alarm” or “atrium.”"

"morphemes, the smallest linguistic units to have semantic meaning"

"more frequent the bigram, the stronger the activation in the letterbox area"

"We should also bear in mind that eye movements, in the course of reading, always draw the relevant words into a narrow area of the visual field, close to the fovea and mostly to the right of it. When we learn to read, only the neurons that code for these locations are given the opportunity to convert to letter and bigram detectors. Indeed, only words presented at the center of gaze, or slightly to the right of it, and at an angle close to horizontal, are efficiently processed by the ventral occipito-temporal pathway.174 Thus only a limited number of neurons are concerned."

"Reading activates a narrow band of cortex, several centimeters long, extending from the back of the brain to the front of the left occipito-temporal sulcus. Functional subdivisions have now been detected in this strip.175 The neuronal code clearly becomes more abstract as it progresses toward the front of the brain."

"visual word form area occupies a relatively extended strip of cortex, whose back end responds to simple letters while the front responds to complex word"

"If my scenario about innate cortical biases is correct, there is no prewired area for reading, but several genetic biases create a gamut of neuronal preferences for different types of visual stimuli. During reading acquisition, visual word recognition simply lands in the cortical location where neurons are most efficient at this task. In all humans, the intersection of genetic gradients creates a single “sweet spot” for letter strings—the letterbox area."

"In spite of their obvious diversity, all writing systems share numerous visual features—highly contrasted contours, an average number of about three strokes per character, and a reduced lexicon of shapes that constantly recur, even in unrelated cultures."

"most characters are composed of roughly three strokes (curves that can be traced without ever lifting or stopping the pen). Variability around this mean is rather low—our capital letters, for instance, have either one stroke (C, I, J, O, S, U), two strokes (D, G, L, P, Q, T, V, X), three strokes (A, B, F, H, K, N, R, Y, Z), or four strokes (E, M, W), but never more."

"I would like to propose that the magic formula of three strokes per character was chosen by our forefathers because it corresponds to the way in which the neurons’ receptive field increases across the hierarchy of visual areas."

"Corroborating Leroi-Gourhan’s statement, in Mesopotamia (present-day Iraq), the birthplace of writing, number symbols played an essential role in the emergence of the written code."

"Each of the letters that we routinely use in our Roman alphabet thus contains a small, hidden drawing dating back four thousand years. An “m” symbolizes waves (mem or mayyūma), an “n” is a snake (nahašu), an “l” a goad (lamd), a “k” a hand with outstretched fingers (kaf), an “R” a head (res) . . ."

"Learning to read involves connecting two sets of brain regions that are already present in infancy: the object recognition system and the language circuit. Reading acquisition has three major phases: the pictorial stage, a brief period where children “photograph” a few words; the phonological stage, where they learn to decode graphemes into phonemes; and the orthographic stage, where word recognition becomes fast and automatic."

"At the age of five or six, when children are exposed to their first reading lessons, they already have an expert knowledge of phonology. They also possess a vocabulary of several thousand words, and have mastered the basic grammatical structures"

"In 1985, the British psychologist Uta Frith introduced a model of reading acquisition that has become a classic and distinguishes three main learning stages.221 This is of course a theoretical simplification, since in fact the three stages are not rigidly partitioned."

"Frith’s three simple steps provide a rough outline of the massive changes that occur in the child’s mind. If nothing else, from the standpoint of pedagogy, they provide a very useful description of the child’s learning curve."

"According to Frith, the first reading stage, which occurs around the age of five or six, is “logographic” or “pictorial.” The child has not yet grasped the logic of writing. The visual system attempts to recognize"

"the child’s brain, at this stage, is attempting to map the general shape of words"

"directly onto meanings, without paying attention to individual letters and their pronunciation—a sham form of reading."

"The development of a grapheme-to-phoneme conversion procedure is characteristic of the second stage in reading acquisition, the phonological stage. At this point, whole words cease to be processed. The child learns to attend to smaller constituents such as isolated letters and relevant letter groups (“ch,” “ou,” “ay” . . .). He links graphemes to the corresponding speech sounds and practices assembling them into words. He can now even sound out unfamiliar words."

"The first years of reading instruction lead to the emergence of an explicit representation of speech sounds. The key stage is the discovery that speech is made up of atoms or phonemes, which can be recombined at will to create new words. This competence is called “phonemic awareness.” Studies by the psychologist José Morais have shown that the discovery of phonemes is not automatic. It requires explicit teaching of an alphabetic code.224 Even adults, if illiterate, can fail to detect phonemes in words."

"In the final analysis, the relation between grapheme and phoneme development is probably one of constant reciprocal interaction or “spiral causality.” The acquisition of letters draws attention to speech sounds, the analysis of speech sounds refines the understanding of letters, and so on in a never-ending spiral that leads to the simultaneous emergence of the grapheme and phoneme codes."

"clearest feature of the orthographic stage is that word length gradually ceases to play a role. At the phonological stage, children slowly decipher words sequentially, one letter at a time. As a result, reading time increases with the number of letters in a word. At the orthographic stage, as reading becomes increasingly fluent, this length effect slowly vanishes. It is essentially absent in expert adults—we all read words using a parallel procedure that takes in all letters at once, at least in short words (eight letters or fewer)."

"In summary, growing parallelism and efficiency are characteristic of the orthographic stage. An increasingly compact word code appears that represents the entire letter string in a single snapshot. This neuronal analysis, organized like a hierarchical tree, can now be effortlessly transmitted in parallel to brain regions that compute meaning and pronunciation."

"Reading time does not depend on word length. It takes us almost the same time to read short and long words, regardless of number of letters (within an interval of about three to eight letters)."

"our visual system simply processes all letters simultaneously and in parallel rather than one after another."

"In young children, however, the process is different. During the first few years of reading acquisition, reading time is strictly related to the number of letters in a word. This word length effect takes years to vanish. The massive impact of the number of letters on young children’s reading time provides clear evidence that reading is not a global"

"Recognizing a whole word can be faster and more efficient than recognizing a single letter. This effect, discovered by Cattell, was replicated by Gerald Reicher and popularized..."

"We are slightly faster at reading words in lowercase than in uppercase."

"Typographical errors that respect the overall contour of a word are more difficult to detect than those that violate it."

"In summary, there is no longer any reason to doubt that the global contours of words play virtually no role in reading. We do not recognize a printed word through a holistic grasping of its contour, but because our brain breaks it down into letters and graphemes. The letterbox area in our left occipito-temporal cortex processes all of a word’s letters in parallel. This fast and parallel processing probably explains why well-known and respected psychologists once propounded theories of global or “syncretic” reading. Today, we know that the immediacy of reading is just an illusion engendered"

"These studies reveal a solid link between early phonological abilities and the ease with which literacy will later be acquired. Most dyslexic children seem to suffer, above all, from a faulty representation of speech sounds. Poor functioning at this level prevents precise processing of spoken words and the consequent pairing with visual symbols."

"In some children, the speech impairment is so drastic that the diagnosis may be different. Pediatricians no longer speak of dyslexia, but of dysphasia or of specific language impairment—yet as soon as these children have phoneme processing deficits, they also tend to suffer from severe reading impairment."

"children learn to read . . . by reading!"

"It is thus essential that children continue to read so that their literacy skills become automatic and enrich their visual vocabulary of graphemes, morphemes, and words."

"reading deficits come from a core impairment in the processing of speech sounds."

"Reading opens up whole new vistas on the nature of the interactions between cultural learning and the brain."

"The neuronal recycling model should extend to cultural inventions other than reading."

"If God existed, he would be a library. —UMBERTO ECO"

"In the case of reading, the hypothetical cultural invariants are concrete and tangible. From Chinese characters to the alphabet, all writing systems are based on a morpho-phonological principle—they simultaneously represent word roots and phonological structures. They also rely on a small inventory of visual shapes shared throughout the world, and first discovered by Marc Changizi (see chapter 4). A broad range of universal, neurologically constrained features underlies the apparent diversity of writing."

"Reading that pleases and profits, that together delights and instructs, has all that one should desire. —JACQUES AMYOT, 1513–1593"

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"Rayner, K., Foorman, B. R., Perfetti, C. A., Pesetsky, D., & Seidenberg, M. S. (2001). How psychological science informs the teaching of reading. Psychological Science in the Public Interest 2:31–74."

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"Rayner, K. (1998). Eye movements in reading and information processing: 20 years of research. Psychological Bulletin 124(3):372–422."

"Rayner, K., Inhoff, A. W., Morrison, R. E., Slowiaczek, M. L., & Bertera, J. H. (1981). Masking of foveal and parafoveal vision during eye fixations in reading. Journal of Experimental Psychology: Human Perception and Performance 7(1):167–179."

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