Research
The Sensory
Basis of Reading and Dyslexia
The following research by John Stein and colleagues, at Oxford University, gives us an insight into what is happening when a dyslexic is reading.
Overview:
Dyslexics have slight impairments in vision and hearing which cause:
- Visual confusion of letter order.
- Auditory confusion of letter sounds.
When we are reading we can break the process into 2 parts.
1. Phonological analysis/sounding out the letters.
2. Direct visual analysis/seeing the whole word.
When reading we use 2 visual pathways, the parvocellular and the magnocellular.
The pathway that concerns dyslexic reading is the magnocellular.
The magnocellular pathway is important for timing and motion.
Research shows that most dyslexics have reduced sensitivity to visual motion.
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This is shown in a test which measures the proportion of random dots that are needed to move in the same direction in order to see the motion of a cloud. Dyslexics are less able to detect the cloud when the proportion of random dots is reduced. |
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This magnocellular deficit is mld, BUT it destabilises eye fixation.
This results in letters appearing to move around and their order becoming confused.
For near vision, when reading the eyes have to converge.
This is known as vergence control.
There is evidence in some dyslexics of fixation wobble, which creates vergence control problems.
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Magnocellular processing sharpens:
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into:
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Studies have shown that where this is the case (around 1/4 of dyslexics), if you eye patch children up to the age of 10 their reading age improves by 3 and 1/2 years. |
Auditory confusion of letter sounds is also a common feature in dyslexics.
An experiment was conducted which measured sensitivity to differences in the frequency between letters of the alphabet.
For example, in the case of the letters b and d, b has a higher frequency than d.
Dyslexics were shown to be less sensitive to the changes in sound frequency and intensity.
This lower sensitivity means dyslexics are less able to sound out words.
This is demonstrated in a test where they are asked to read out nonsense words.
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Examples
of words:
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tegwop blint plomt peltip visht sint |
Dyslexics have difficulty sounding out these isolated nonsense words.
This has a direct impact on a person's reading ability.
To recap, dyslexics have slight impairments in vision and hearing which cause:
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Visual confusion of letter order.
- Auditory confusion of letter sounds.
The results of this research should help us to develop:
- Tests in prereaders to predict which children will go on to have problems learning to read.
- Remeditation programmes targeted at each child's specific problems.