The most common myth about dyslexia is that it results from a problem with vision. One often hears that individuals with dyslexia read words “backwards” or they read pages from right to left rather than left to right. To this point there is no credible scientific evidence that dyslexia results from a vision problem.
One also can find claims that dyslexia is caused by dietary issues and that it can be treated by controlling dietary intake. Again, there is no credible evidence that diet has anything to do with dyslexia.
Rather, as will be seen later in these pages, dyslexia is caused by a problem learning and processing the Individual sounds that allow us to produce spoken language.
The language we use is made up of individual sounds that are called phonemes. Children who will become dyslexic have difficulty in accurately learning the phonemes that make up their language. One way to think about this difficulty is to imagine two audio tape recorders; one that is expensive that captures sounds with great clarity and precision, and a second cheap one that blurs the distinction between similar sounds. Individuals who will typically become good readers are equipped with the expensive sound recorder while individuals who will become dyslexics are equipped with the cheap recorder. The cheap recorder is akin to having a phonological core deficit, which is described below.
Difficulties in learning the sounds that make up language (phonemes) have a number of early consequences that precede difficulties in learning to read. One consequence is that children who will develop dyslexia sometimes have delays in learning to speak, and they sometimes develop difficulties in correctly pronouncing words when they do speak. Difficulties in correctly pronouncing words are called articulation disorders and many children who are identified with articulation disorders receive speech therapy to correct the difficulties. Speech therapy may not, however, correct the source of the problem and children who successfully get beyond articulation problems may still develop dyslexia.
Learning to read typically follows a sequence of skill development beginning with learning the names of letters and ending with the ability to effortlessly extract the meaning from sentences, paragraphs, and even books. There are several important steps though between the starting and ending points. After learning the names of letters, most children learn the sounds that letters make, and then they must learn to automatically identify words in context so that they can comprehend what they are reading. Individuals with a phonological core deficit find it very difficult to learn reading skills that involve attaching sounds to letters and words. The difficulty in attaching sounds to letters and words, delays, and in some cases, blocks the development of skilled reading comprehension.
Normal readers quickly move from sounding out words to automatically recognizing words. Automatic word recognition means that there is no thought involved in word recognition; the reader looks at a word and the meaning of the word automatically pops into the reader’s conscious awareness. Dyslexic readers have difficulty attaining this automatic state and typically struggle with word recognition.
The reason for the struggle with word recognition relate back to the phonological core deficit problem. When we read we have specialized processing mechanisms in our brains that quickly (very quickly) transform letters and letter sequences into sounds and then transfer those sound patterns to the speech recognition areas of the brain. In essence, reading is word decoding (transforming letters making up words into sound patterns) plus speech comprehension. The phonological core deficit that prevents the easy capture of phonemes also inhibits the rapid transformation of letter sequences into sounds that can then be interpreted by the speech processing area of the brain.
A phonological core deficit makes it difficult to learn the sounds making up the words in a language. The deficit can make it difficult to learn to speak and can make it harder to correctly pronounce words in the language a child is learning. A phonological core deficit makes it difficult for children to discriminate between closely related sounds such as those formed by the letters “b” and “p.” Not being to hear close distinctions may delay speech learning and may create a situation where the child cannot hear the mispronunciation he or she is making.
Here, for example, is a conversation with a child who may have a phonological core deficit:
Parent: What is this?
Child: A phish.
Parent: No, fish!
Child: That is what I said, phish!!
Difficulties with sound capture may also have a major impact on learning to read. When children begin to learn letter sounds they often make a very important discovery—the sounds that letters make map onto the sounds contained in spoken words. Researcher call this discovery “the alphabetic principle,” meaning that the child realizes that the individual sounds that letters make can be combined to form the words used when speaking.
A skill that develops after letter sounds are learned is the ability to manipulate the sounds that letters make. For example, a child develops the ability to sound out letters and to then rapidly blend those sounds so that he or she can recognize the word. Children also develop the ability to identify words by adding or deleting letters. This is called “phonological awareness.” A child who has phonological awareness can tell if two words rhyme, or what the word “cat” would sound like if the letter “s” was added at the beginning of the word.Phonological core deficits inhibit the ability to acquire phonological awareness.
The ability to learn letter names, the sounds of letters, and the ability to manipulate those sounds using phonological awareness skills are important precursors to learning to read. Difficulties in learning these skills are important predictors of reading difficulties. Children who develop dyslexia often display an insensitivity to rhyme as contained in nursery rhymes, they are slow at learning letter names and letter sounds, and they have difficulty acquiring the skills that underlie phonological awareness. These difficulties can all be traced back to a phonological core deficit that was probably present at birth.
Phonological core deficits, and hence dyslexia, probably has a biological basis that is genetic in origin. Reading difficulties tend to run in families, most often on the father’s side of the family. Moreover, there appears to be sex differences in dyslexia with 3 out of 4 of formally diagnosed dyslexics being male.
Dyslexia is characterized by a difficulty in learning to read, but normal performance in other intellectual and academic areas. The discrepancy method of diagnosing dyslexia involves administering reading tests and general measures of intellectual performance (e.g., an IQ tests) and determining if there is a discrepancy between the two. That is, normal performance on the intelligence tests and poor performance on the reading test. The discrepancy procedure is the traditional way of identifying individuals with dyslexia. However, the discrepancy method has critical flaws and more modern procedures have been suggested as diagnostic procedures.
Response to Intervention Is the procedure most commonly used in today’s school system and is the procedure recommended by federal legislation. RTI involves screening all children at the first-grade level to identify children who are deficient in skills (e.g., phonological awareness, letter naming letter sound naming) that are important for the development of skilled reading. These children are then separated from peers and given focused group instruction in missing skills.
Typically, in the second grade another screening test is administered and children who remain well behind peers are given another round of intense instruction (called best practice instruction), perhaps involving one-on-one instruction with a reading professional. This more intense level of instruction may continue through the third grade. If after three years of best practice instruction the child still is well behind peers in reading development the child is diagnosed as having dyslexia.
Another method for identifying dyslexia is the used in the Reading Success Lab software. This method involves a series of reading tasks and examination of the performance profile on the tasks.Here is an image of the cognitive profile diagnostic method:
The graph shows the grade level percentile performance of a typical dyslexic child. The child has normal performance on tasks that measures the speed and accuracy of identifying stars and plusses and letters of the alphabet. However, the speed and accuracy performance on tasks that measure word identification, nonword identification, word meaning, sentence understanding and reading comprehension are well below average for grade level. Notice, however, that listening comprehension is perfectly normal.
The cognitive profile method can identify superior readers, average readers, poor readers who do not have dyslexia, readers who may have an attentional disorder, readers who may have a global cognitive deficit, and readers who likely have dyslexia.
A final procedure that could be used to identify dyslexia is to take a child to a medical or research facility that can conduct fMRI analyses. fMRI is a medical technique that allows a researcher to see what parts of the brain are active when an individual is reading. Individuals with dyslexia typically have different patterns of brain activation than do normal readers, and this difference can be used to identify readers who are dyslexic At this time fMRI analysis is strictly a research procedure and is not used for diagnostic purposes.
Research has shown that up to 20% of children beginning school in the U.S are at-risk for developing a reading problem. The most effective procedures for correcting reading problems are those that are implemented early. There is a substantial body of research showing that intensive early screening procedures that identify and then remediate weak letter identification skills, weak letter sound skills, weak phonological processing skills, and weak word decoding skills can reduce the population of reading problems to approximately 5% of the total population of readers in our schools. There is a good chance, however, that the 5% of readers who do not respond well to early interventions are readers who have truly have dyslexia.
Schools that do not offer early screening and early intervention programs often wait until 3rd grade, or even beyond, to identify readers who may be dyslexic. Almost all students who are formally identified as having a specific reading disability (dyslexia) receive treatments that are based on some type of phonics-based instruction. Phonics based interventions are based on the premise that problem readers have difficulty in attaching sounds to letters and to then blend sounds to identify words. Phonics based interventions work well for some children, but certainly not for all children. In fact, there is the possibility that continued use of phonics with dyslexic children may even be harmful with respect to the ultimate development of skilled reading.he problem is that these children begin to utilize word sounding out strategies for nearly every word they read.This results in a child who can identify words with excellent accuracy but do it so slowly they have no possibility of comprehending what they are reading.
The procedures utilized in the Reading Success Lab software do work with these children. (See the scientific article by Royer and Walles)