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What is Dyslexia?
An Extreme Difficulty in Learning to Read
Dyslexia is one of the reasons children have trouble learning to read. It is distinct from other difficulties.
Dyslexia causes a problem learning phonemes, the separate sounds that make up speech. Dyslexia is a brain processing issue, not a hearing issue. The brain blurs the phonemes and what the child hears. This blurring continues to interfere with the ability to attach sounds to letters and words, making learning to read very difficult. Difficulty recognizing phonemes is called a “phonological core deficit”.
More about Phonemes
All languages consist of a set of sounds, called phonemes that make up the language. The English language has 44 phonemes. Other languages may have different phonemes and a different number of phonemes.
Many languages have phonemes that do not exist in English. Those phonemes are often difficult for English speakers to hear because the brain has not been trained to recognize them.
Phonological Core Deficits
Children with difficulty learning phonemes often display a variety of problems such as:
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Delays in learning to speak
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Articulation Disorder – Difficulty correctly pronouncing some words when they speak. This often results in a child having speech therapy before entering school
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When of appropriate age, difficulty learning nursery rhymes and rhyming activities
More Info About Phonological Core Deficits
Phonological core deficits, like dyslexia, have a biological and genetic origin. Reading difficulties tend to run in families, most often on the father’s side of the family.
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.
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 able 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.
An example of 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!!
The child in the above example not only blurs the sound of the word the parent is speaking, he also blurs the sound of his own pronunciation. Difficulties with sound capture will 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.
Phonological Core Deficits and Learning to Read
Important steps in learning to read:
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Learning letter names.
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Learning the sounds that letters make.
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Automatically recognizing words.
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Automatically extracting the meaning from sentences, paragraphs, and even books.
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.
Dyslexia and Word Reading
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 their conscious awareness.
Dyslexic readers have difficulty attaining this automatic state and typically struggle with word recognition.
More About Dyslexia and Word Reading
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.
Many people while reading actually hear a voice speaking the words they are reading.
Phonological Awareness and Phonological Core Deficits
After learning letter sounds a child develops the ability to sound out letters and then to rapidly blend those sounds to recognize words.
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.
More About Phonological Awareness and Phonological Core Deficits
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.