Reading in the Brain: The Science and Evolution of a Human Invention
- Stanislas Dehaene
Reading is a vital portal to knowledge. Unique to humans, this evolutionarily recent invention intertwines language and vision in such a new way that years of education are needed to become fluent. The written word occurs in a dazzling variety of writing systems, from Roman and Greek alphabets to Chinese and Japanese characters, reflecting both universal similarities and the idiosyncratic evolutions of different languages. In his accessible and provocative book Reading in the Brain, cognitive neuroscientist Stanislas Dehaene explains how our brain empowers us to read.
A leading researcher in this field, Dehaene views reading as a tour de force of the human brain that is intellectually fascinating and important for education. Understanding how we read requires consideration of many themes: psychology, the organization of vision and language in the brain, primate neurophysiology and its evolution, the history of writing, the development of the child's mind and brain, and cultural variation. The book weaves these aspects into a compelling synthesis.
Dehaene describes pertinent neurological cases, such as that of a man with word blindness. After having a stroke, the man's vision was intact and he could hear, speak and write down dictated words, but he couldn't read words, not even those he had written himself. Dehaene explains that when we read, we visually process about 12 letters at a time. He reveals the neural architecture of reading, describing the role of brain regions such as the 'letterbox', in which printed words are recognized as the gateway to meaning.
A theme throughout the book is how reading involves a balance between evoking the sound of a word in spoken language and rapidly translating print to meaning. The competing auditory and visual demands produce two interactive pathways in the brain — a phonological route that translates printed words to sound and then meaning, and a direct route that translates print to meaning. The reading system is so impressive that we can identify a word, from among the 50,000–100,000 words that we know, in a mere 50 thousandths of a second.
Dehaene then takes us on a global tour. Languages vary markedly in how they are written down and how that print relates to sounds and words. In Italian, letters or small groups of letters — known as graphemes — correspond almost on a one-to-one basis to the smallest linguistic units of sound, or phonemes, with about a 33:25 ratio of graphemes to phonemes. By contrast, on account of its complex history, the English language has to ascribe a greater variety of sounds using the same alphabet. Thus it contains many irregularities, such as the evocation of different sounds with the same letter. This results in about a 1,120:40 ratio of graphemes to phonemes. In Mandarin Chinese, thousands of characters reflect the mixture of words and information about pronunciation.
This variation in writing systems has profound effects on education. A child becomes a skilled reader in Italian in about a year, in English in about three years, and in Mandarin Chinese in about a decade. Cultural variation places different demands on brains that share universal principles of organization.
Dehaene is forthright about how scientific evidence about reading can contribute to educational policies and practices, and about the limits of such contributions. He argues that children should be taught 'phonics' as a core component of initial reading — a learning process that connects the sounds of spoken language with individual or groups of letters in alphabetic languages. He also explains how evidence for the contrasting method of 'whole-word' reading was misunderstood in promoting its most extreme versions.
The book ends by exploring two fascinating topics. First, Dehaene considers the remarkable frequency with which children reverse the writing of letters. He argues that this developmental phase may reflect a residual consequence of our specialized ability to recognize print, emerging from our general ability to recognize visual objects. Second, he considers how reading may be one case of a uniquely human brain capacity to create new cultures, thanks to neural systems that support multimodal integration, abstract thoughts and our ability to represent the intentions and beliefs of others — known as the theory of mind. It takes a powerful theory of mind for the writer to imagine what can be communicated to the reader.
Dehaene's masterful book is a delight to read and scientifically precise. It is vibrant with intellectual curiosity, fascinating perspectives and amusing examples. Reading in the Brain is compelling for anyone who is curious about how we read.
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Gabrieli, J. Deciphering the printed word. Nature 463, 430–431 (2010). https://doi.org/10.1038/463430a