Is a specific learning
is often characterized by
difficulties with accurate
word recognition, decoding
and spellingmay cause problems
slow down vocabulary
is not the result of
is not linked to
the child, despite having normal intelligence and receiving proper teaching and parental
support, has difficulty learning to read.
Learning to read
the child learns to crawl, walk, talk, throw or catch things, ride a bicycle later than the majority
of other kids.
apart from being slow to learn to speak, the child commonly mispronounces words, finds
rhyming extremely challenging, and does not appear to distinguish between different word
at school the child takes much longer than the other children to learn the letters of the
alphabet and how they are pronounced. There may also be problems remembering the days of
the week, months of the year, colors, and some arithmetic tables.
Slow at learning sets
the child may seem clumsier than his or her peers. Catching a ball may be difficult.
the child commonly gets "left" and "right" mixed up.
Left and right
numbers and letters may be reversed without realizing.
may not follow a pattern of progression seen in other children. One word may be spelt in a
variety of ways on the same page.
phonology refers to the speech sounds in a language. If a word has more than two syllables,
phonology processing becomes much more difficult.
children with dyslexia commonly find it hard to concentrate for long, compared to other
More about dyslexia
It is now well established
that dyslexia is a
neurological disorder with a
FMRI and behavioral experiments have generated
significant results so as to suggest the disorder be
viewed as having neurological causes.
has uncovered clear
evidence of biophysical
and structural anomalies
in individuals who are
…But its actual mechanisms are still mysterious and currently
remain the subject of intense research endeavour in various
neuroscientific areas and along several theoretical frameworks.
Indeed, there are no less than three major
theories of dyslexia.
Explains that the origin of the disorder is a congenital
dysfunction of left‐hemisphere perisylvian brain areas
underlying phonological representations, or connecting
between phonological and orthographic representations.
Bradley and Bryant (1978)
The phonological theory
postulates that dyslexics have a
specific impairment in the
representation, storage and/or
retrieval of speech sounds.
Dyslexics’ reading impairment by
appealing to the fact that learning to
read an alphabetic system requires
learning the grapheme–phoneme
If these sounds are poorly represented, stored or retrieved, the learning of
grapheme–phoneme correspondences, the foundation of reading for alphabetic
systems, will be affected accordingly
Specifie that the primary deficit lies in the perception of short or
rapidly varying sounds. The original version of the auditory theory
made no particular claim at the biological level, but abnormal
neurophysiological responses to various auditory stimuli have also
Tallal and Piercy (1973)
Support for this theory arises from evidence
that dyslexics show poor performance on a
number of auditory tasks, including frequency
and temporal order judgement.
The failure to correctly represent
short sounds and fast transitions
would cause further difficulties in
particular when such acoustic
events are the cues to phonemic
There is indeed also evidence that
dyslexics may have poorer
categorical perception of certain
A visual impairment giving rise to difficulties with the processing of
letters and words on a page of text. This may take the form of
unstable binocular fixations, poor vergence or increased visual
Logrelove et al (1980)
The visual theory does not exclude a phonological deficit, but
emphasizes a visual contribution to reading problems, at least in some
The theory postulates that
the magnocellular pathway
is selectively disrupted in
certain dyslexic individuals,
leading to deficiencies in
visual processing, and, via
the posterior parietal
cortex, to abnormal
binocular control and
Here the biological claim is that the dyslexic’s cerebellum is mildly
dysfunctional and that a number of cognitive difficulties ensue. Evidence of
poor performance of dyslexics in a large number of motor tasks in dual tasks
demonstrating impaired automatization of balance, and in time estimation,
a non‐motor cerebellar task, is shown by brain imaging studies, they have
also shown anatomical, metabolic and activation differences.
Nicolson and Fawcett (1990)
Cerebellum plays a role in motor control and
therefore in speech articulation. It is postulated
that retarded or dysfunctional articulation would
lead to deficient phonological representations
Cerebellum plays a role in the
automatization of overlearned
tasks, such as driving, typing and
reading. A weak capacity to
automatize would affect, among
other things, the learning of
Finally, there is a unifying theory that attempts to integrate all the findings
mentioned above. A generalization of the visual theory, the magnocellular
theory postulates that the magnocellular dysfunction is not restricted to the
visual pathways but is generalized to all modalities (visual and auditory as
well as tactile). Furthermore, as the cerebellum receives massive input from
various magnocellular systems in the brain, it is also predicted to be
affected by the general magnocellular defect.
Stein and Walsh (1997)
Through a single biological cause, this theory therefore manages to
account for all known manifestations of dyslexia: visual, auditory,
tactile, motor and, consequently, phonological.
Beyond the evidence pertaining to each of the theories described previously,
evidence specifically relevant to the magnocellular theory includes magnocellular
abnormalities in the medial as well as the lateral geniculate nucleus of dyslexics’
brains, poor performance of dyslexics in the tactile domain and the co‐occurrence
of visual and auditory problems in certain dyslexics
Dyslexia is not a disease. We live in a society where reading and
writing are integral parts of everyday life - interventions that help
people with dyslexia are aimed at improving their coping skills.
Some people claim that dyslexia is part of our differences, here is a nice
video about it.