What causes dyslexia?

Dyslexia (the brain’s inability to read, write and spell with ease) has many causes, not all of which apply to every impaired reader.

In people with dyslexia, nerve cells in the brain are thought not to work well together in order to achieve reading. Or those cells might cooperate, but at slower rates than for average readers. Why?


What might cause dyslexia?


faulty genes

brain injuries

problems connecting sounds to symbols

blockage of brain pathways

using the right hemisphere for left hemisphere functions

migrating neurons

hearing problems

unskilled reading teachers


  • Genetics might play a role for some readers. Defects in a gene known as DCDC2 and its interaction with another gene, KIAA0319, have been identified as related to dyslexia, according to researchers at Yale University.
  • Physical problems in certain parts of the brain might cause dyslexia. Sections of the brain specializing in language or vision, in particular, are needed to see letters; to associate those letters with sounds, syllables and words; and to derive meaning by combining words into sentences. If one part of the brain used in reading is damaged, dyslexia could result. Injuries to parts of the brain might have occurred before birth—a stroke, for example—or they might have happened after birth—a fall, for example.
  • Problems identifying sounds within words and connecting those sounds to letters or to letter patterns is the most studied possible cause of dyslexia. Children with this problem have trouble sounding out c-a-t. When they hear words like “Tyranasaurus Rex,” they don’t hear syllables or individual letter sounds; they hear words. No problem. But when they learn to read, they must take the sounds inside words apart and attach letters to those sounds and put the letters back together again to know words. For some people, this is hard.
  • Failure (blockage?) of the pathways normally used in reading could be a cause of dyslexia. Or weakness at connecting points along the brain’s pathways could cause slow processing.
  • While most readers use the left hemisphere of the brain in a dominant way when reading, it is thought that some dyslexic readers might use the right hemisphere more dominantly, or they might use both hemispheres equally. If so, reading becomes a labor-intensive undertaking.
  • Some researchers think that when the brain is developing, neurons that should be part of one section of the brain “migrate” to another spot in the brain and develop there. When a reader tries to access those cells, they are not where they are supposed to be, hampering the reading process.
  • Young children who have hearing problems might develop a life-long problem associating sounds with symbols for those sounds, resulting in dyslexia.
  • A well trained reading teacher who can identify anomalies in a child’s struggle to read can’t undo the above problems, but she can suggest strategies to lighten or even overcome some of these problems. However, if a child’s teacher is not savvy concerning strategies in the field of reading, the child might flounder. A teacher isn’t the cause of dyslexia, but her lack of skill can make the child’s struggle to read harder.

Reading is about a 6,000-year-old activity for human beings, a new activity in the evolution of the brain. The brain is not programmed to read any more than it is programmed to sing opera. Rather, in learning to read, we humans use parts of the brain which our non-reading ancestors used for something else—seeing and speaking, for example. Those same pathways which evolution streamlined for one purpose are now being used for additional purposes relating to reading, writing and spelling.

Work with brain imaging technology is revealing to researchers the parts of the brain involved in dyslexia. Work with the genome is revealing gene interactions which might have an effect upon reading. The answer to your question—What causes dyslexia?—is the brain and the complicated way in which the brain works.

For detailed information on some of these causes, read expert Maryanne Wolf, Ph.D., author of Proust and the Squid; The Story and Science of the Reading Brain.

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