Among the many challenges faced by children with dyslexia (and by their parents and teachers) is the nagging fear that their difficulties with reading are entirely hard-wired: predetermined by their genes and impossible to change. Recent research offers a balm for that fear. It suggests that experience plays a big role in dyslexia, both in exacerbating reading problems and, potentially, in easing them.
Dyslexia is the most common learning disability in the United States, affecting more than 10 percent of the population. Its cause has remained a mystery, however, and over the years scientists have advanced many theories about the biological mechanism leading to dyslexic people’s struggles with reading. Recent research has moved us closer to an understanding of where dyslexia starts and how it develops, illuminating the nature of reading itself along the way.
One longstanding hypothesis about the origin of dyslexia, for example, proposes that the disability stems from deficits in the visual system. Problems with vision might explain why dyslexics sometimes confuse d’s with b’s, or why they substitute one word for another. And indeed, brain scans show less activity in the visual regions of dyslexics’ brains than in the brains of normal readers.
Research led by Guinevere Eden, director of the Center for the Study of Learning at Georgetown University Medical Center, has recently cast serious doubt on this theory. Dyslexia is not a problem of seeing, she contends, but a problem of processing language, of assembling individual sounds into words. Ms. Eden maintains that we should not be focusing on the visual system as we diagnose or treat dyslexia.
But what about those visual deficits, consistently found in dyslexics? Researchers like Ms. Eden have advanced a fascinating explanation for them, one that helps reveal the workings not only of dyslexia, but of normal reading as well.
One of Ms. Eden’s colleagues at Georgetown, Olumide Olulade,notes that reading is a “culturally imposed skill.” That is: Human beings did not evolve to read, as we evolved to naturally and easily understand and produce spoken language. Every one of us who has become literate has had to change our brain significantly to turn the black squiggles on this screen into meaningful symbols. The more we read, the more our brains change.
But in children who have dyslexia, the initial stages of this brain change do not proceed as in other children’s brains.
Recent research led by Bart Boets, of the Catholic University of Leuven in Belgium, indicates that the brains of dyslexics do form accurate neurological representations of language sounds. (This would explain why dyslexics have no trouble understanding spoken language.) When dyslexics go to put together these sounds into words, however, communication between the auditory and language centers of their brains seems to break down. Dyslexia, Mr. Boets and his colleagues say, is a “disconnection syndrome.”
This disconnection makes reading difficult for dyslexic children from the very beginning. Because reading is so hard, they do it less. And because they read less, their brains change less. Visual deficits, according to the latest thinking, are not the cause of dyslexia. They are a result of less reading, of experience. And experience of the right kind — intensive tutoring in phonological and orthographic skills — can undo these visual deficits, the research of Ms. Eden shows, as well as significantly improve children’s reading skills.