Perception and dyslexia mr patrick mulcahy chair asasa
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Perception and Dyslexia Mr Patrick Mulcahy, Chair ASASA. Perception is the process of acquiring, interpreting, selecting, and organising sensory information Brain is the organ of perception Neurological processing underlies our perception. Perception.

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Perception and Dyslexia Mr Patrick Mulcahy, Chair ASASA

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Perception and DyslexiaMr Patrick Mulcahy, Chair ASASA

  • Perception is the process of acquiring, interpreting, selecting, and organising sensory information

  • Brain is the organ of perception

  • Neurological processing underlies our perception


  • Darwinian natural selection over countless generations has shaped our sense organs.

  • They have been shaped to give us a useful picture of the world, to help us to survive.

  • What sense organs do is to construct a useful model of the world…a kind of virtual reality simulation of the real world.

  • Very difficult to free oneself from the shackles of pre-conception and ‘common sense’.


  • If reality was represented as the keys on a piano, human perception would be limited to a single chord

Developmental Dyslexia

  • Professor John Stein, Magdalen College, Oxford, states that ‘dyslexia has an organic neurological basis and, contrary to previous strongly held beliefs, it is not 'purely psychological’

  • Professor Stein sees a definite correlation with abnormal magnocellular neurones

Magnocellular Region

Correlation with Dyslexia: Sound and vision being processed differently in this one area of the brain with tasks involving literacy

There are two partially independent mechanisms for reading:

phonological and visual.

Reading and Perception

  • Saying the colours rather than reading the words demonstrates the separate processes

The Phonological Model

  • The phonological model of dyslexia defines it in terms of difficulties associated with converting phonemes (‘smallest meaningful segment of language’) into symbols (letters).

  • The mental activity associated with reading can be divided into word identification, phonological processing, and cognitive reasoning.

  • A deficit in phonological processing will reduce a person’s ability to convert symbols into sounds (reading) and/or sounds into symbols (writing) thus preventing them from exhibiting their true cognitive ability.


  • Different combinations of 44 phonemes produce every word in the English language as with the example used above i.e.

  • CAT = ‘Kuh’, ‘aah’ and ‘tuh’.

  • Before words can be identified, understood, stored in memory or retrieved from it they must first be broken down or parsed, into their phonetic units by the phonological module of the brain.

  • There is no overt clue to the underlying segmental nature of speech and speech appears seamless, i.e. an oscilloscope would register the word ‘cat’ as a single burst of sound


  • Reading is not natural as it is a human invention which must be learned at a conscious level. A child has to learn that orthography (the sequence of letters on the page) represents the phonology. This is what occurs when a child learns to read.

  • When a child has dyslexia, a deficit within the language system of the phonological module impairs his/her ability to segment the written word into its underlying phonological components. The deficit in phonological can prevent word identification.


  • Difficulties with rote memorisation;

  • Difficulties with rapid word retrieval;

  • Difficulties with reading – decoding words automatically can be difficult and the additional energy consumed on this tends to lessen comprehension i.e. students with dyslexia rely more on context when reading and this slows them down;

  • Spelling difficulties can be similarly accounted for as the same process is used when converting sounds into symbols (writing);

  • The additional work required by the brain to decode symbols can result in tiredness and concentration can consequently suffer



Reading requires a series of eye fixations and saccades to the next word.

How could a visual magnocellular deficit cause reading problems?

  • The magnocellular deficit in dyslexics is mild.

  • Hence letters appear to move around and their order becomes confused

Magnocellular processing sharpens:




  • Difference in the area of the brain affecting visual and phonological processing

  • The net result of this is that their perception of literacy will be different.

Student with Dyslexia

Non-Dyslexic Student

Brain Mapping reveals that people with dyslexia rely on different parts of the brain when reading and writing.

The Needs of Students with Dyslexia

  • Context is Higher Education

  • Research, Composition, Proofreading, Note-taking and Time Management

  • Teaching is Lecture-based

The Needs of Students with Dyslexia

  • Students with Auditory Sequential Working Memory and Visual Memory Deficits need Different teaching and Learning strategies

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