Before I go to the specifics of remedial intervention - the "treatment" for dyslexia - I need to explain two fundamental concepts related to reading: one involves spoken language, and the other involves written language.
Before a child begins to read, he must understand that spoken words come apart and that they are made up of very small bits of language. These tiny particles of language are called phonemes, and the development of this insight about words is called phonemic awareness. Once a child appreciates that spoken words can be pulled apart into distinct sounds, he is well on his way to solving the spoken language part of the reading code. The he is ready to take the next big step: figuring out how printed letters link to these sounds - for example, knowing the first sound of the spoken word sat, sss, is represented by the letter s, and the final sound t by the letter t. And then one day he solves the puzzle: he makes the critical insight that the written word sat has the same number and sequence of sounds, sss, aaa, t as the spoken word sat and that the letters represent these sounds. He has broken the reading code! The child has mastered the alphabetic principle. He is ready to read.
This step is extremely important because once the child knows the code, printed words are no longer a mystery. He has a strategy; he knows how to link the letters to the sounds they represent and then to blend the sounds together to read the word. He applies his knowledge of how letters relate to sounds to analyze and to read more and more unfamiliar words. This is referred to as decoding. The better a child gets at decoding words, the more accurate his reading. A child who knows how to sound out printed words is freed from having to memorize every word he wants to be able to read. Sounding out words allows him to unlock the mystery of reading and to read words he has never seen before.
Several studies since the early 1990s have demonstrated that phonological deficits are the most significant and consistent marker of dyslexia in children. In these studies, dyslexic children are typically asked to divide specific words into phonemes and are then asked to delete a specific phoneme. For example, a child must say rock without the rrr sound. Dyslexic children, as compared to non-dyslexic children, have greater difficulty with this phoneme deletion task or are unable to do it.
A related test asks the child to read so-called nonsense or made-up words: she would never have seen these words before and could not have memorized them. We might begin with ree, ip and viv. The words increase in difficulty to rejune, depine and gern, and then to the most challenging of all: pnir, ceisminadolt and byrcal. The point of these strange but pronounceable words is that they test a child’s ability to "sound out words", that is, to map letters to sounds. Each word can be sounded out if you have acquired what is referred to as "phonological decoding" ability. The results from these studies indicate that the deficiency in phonological awareness and decoding demonstrated by dyslexics is fundamental to their lower reading ability.
Before higher-order remediation can begin, a dyslexic must have mastered these two basic elements of reading - phonemic awareness and decoding. If he has not, he will need systematic and direct instruction in these two areas before the next steps described in Part II can begin.