Canadian Dyslexia Centre

A Definition of Dyslexia

Dyslexia is a hereditary condition which makes reading, writing and spelling in one’s native language extremely difficult, despite average or high intelligence, good education and adequate sociocultural conditions.

A Learning Disability?

The term “learning disability” is non-specific; it encompasses many conditions that impede knowledge acquisition. The following definition is used only for legislative, financial and pedagogical purposes. It is not a definition of dyslexia, which is more defined as a specific learning disability.

Neurobiological Causes

Recent research has found a hereditary component to dyslexia.

Dyslexia stems from a neurological difference, i.e., a different functioning of the brain. Dyslexic people have a larger right cerebral hemisphere than “normal” readers. This can explain the fact that dyslexic people often display talent in fields associated with the right hemisphere, such as the arts, sports, mechanics, music, 3D visualisation, creative problem solving and intuition in human relationships.

Not only do dyslexic people have a unique cerebral structure, they also have unusual “connections” in their brains. Their neurons can be found in unexpected configurations and are not structured as precisely as in non-dyslexic brains.

Aside from the particularities in their neural and cerebral structures, studies performed using magnetic resonance imaging (MRI) show that dyslexic people do not use the part of the brain that is consistently associated with reading among the other types of readers. In fact, there is very little uniformity regarding the part of the brain they use.

We can therefore assume that dyslexic people do not use the most efficient part of their brains to read. This function is rather put under the charge of another part of the brain.

Phonemic Awareness

The renowned researchers at the National Institutes of Health say the following:

“ Phonemic awareness is more highly related to learning to read… than tests of general intelligence, reading readiness, and listening comprehension. ”

Children with phonemic awareness difficulties have challenges in distinguishing between or manipulating the different sounds that make up syllables or spoken words. They are therefore unable to perform the following exercises:

  • Phoneme segmentation
    E.g.: What sounds can we hear in the word “bag”? – What is the last sound in the word “sea”?
  • Phoneme elimination
    E.g.: What word would remain if we removed the sound /r/ from the word ‘roar’?
  • Phoneme comparison and association
    E.g.: Do the words ‘glue’ and ‘gap’ start with the same sound?
  • Phoneme numbering
    E.g.: How many sounds are there in the word ‘arm’?
  • Phoneme replacement
    E.g.: What word do we get when we replace the /p/ sound in the word ‘papa’ with the /m/ sound?
  • Sound integration
    E.g.: What word do we get if we put together the sounds /p/, /a/ and /r/?
  • Rhymes
    E.g.: Find the most words you can that rhyme with ‘wall’.

If a child lacks phonemic awareness, he or she will have trouble understanding the relationships between the letters of a word and the sounds these letters make. It will also be difficult for him or her to use the relationships between letters and sounds to pronounce the sounds that make up a new word.

As such, kindergarten students who have poor results in the course of activities aiming to develop phonetic awareness will very likely show difficulties acquiring the skills necessary for early word reading. These skills are the basis of learning to read in elementary school.

The skills related to phonemic awareness can and must be taught to children with learning difficulties in this area in a direct and explicit manner.

Research by Sally Shaywitz, co-director of the Yale Center for the Study of Learning and Attention, has demonstrated that to learn to read, all children must develop phonemic awareness, that is, they must discover that the words of spoken language can be broken down into smaller units of sounds called phonemes, and that the words of written language are made up of letters that represent those sounds.

Among dyslexic people, the part of the brain that processes phonemes is different. Since this represents the most basic step in the reading process, all subsequent steps are challenged even if the parts of the brain that control them are intact.

In other words, using a computer analogy, how can we expect the information to be processed if the circuit responsible for data entry works differently or not at all?

See our publications for more information!

our publications