PS2011 & PS2016 Cognitive
Psychology – Dr John Beech
Developmental Dyslexia
Definitions of dyslexia
Definitions
• Hinshelwood (1900): “word blindness”.
• Orton (1937) “strephosymbolia” (“turning of symbols”).
• “Dyslexia” - late 19th C: German dys “difficult” and Greek
lexis “speech”. Made popular by Samuel Orton, a
neuropathologist.
• “Dyslexia” means that a child is:
1. Below normal in reading “age”.
2. In average range of IQ.
3. No visual nor auditory problems.
4. Emotionally stable.
5. Normal educational opportunity.
2
Definitions of dyslexia
• The term “dyslexia” can also be applied to adults in the
context of their reading level being below what would be
expected for their level of IQ.
• Dyslexia in children is referred to here as “developmental
dyslexia” to differentiate from “acquired dyslexia”, which
we’ll examine briefly after the current topic.
3
Definitions of dyslexia
Vellutino (1979) suggested for experiments:
1. 2 years behind in reading
2. WISC-R: >90 (Mean 100)
3. Acuity in sight and hearing
4. Not maladjusted
5. Only from middle class areas
These are exclusionary criteria
4
Definitions of dyslexia
Nowadays for assessment purposes in UK:
1. Statistically significant discrepancy on WORD reading
tests on expected v. observed scores, based on the
WISC-IV. Known as the “discrepancy measure” to
obtain dyslexia.
2. No problems in sight, hearing or maladjustment
Thus there is a little bit of confusion with the use of the term
“dyslexia”. The educational establishment in the UK can
tend to lump in children who are behind in reading, who
are also weak in IQ.
5
Characteristics of dyslexia
Some reported characteristics
1. 4:1 boys:girls
2. Problems with time, naming sequences (e.g. months)
3. Left/right reversals (e.g. was/saw, b/d, p/q)
4. Problems with differentiating the left from the right
5. Difficulty in repeating things
6. Problems in understanding spoken directions
7. Problems in remembering what has just been said
8. Poor handwriting
9. Minor neurological impairments
6
Characteristics of dyslexia
Is dyslexia anything special?
• It sounds like a medical label, but doesn’t explain the
condition. All it does is exclude possibilities.
• Dyslexia has not been conclusively linked to brain
damage so far, except that there is more brain symmetry
in poor readers. But 35% of everyone has this.
• The rationale behind dyslexia is that if a child is poor at
reading AND has normal or above average IQ, then that
child has dyslexia.
• But outside the frame of dyslexia is the child who is poor
at reading AND has low IQ. We would expect reading
to be poor if IQ is also low – as shown in the Isle of
7
Wight study…
Characteristics of dyslexia
Isle of Wight study (Michael Rutter et
al., 1970; Rutter & Yule 1975)
• Examined all 9-11 yrs children on Isle
of Wight
• Correlation between mental age and
reading: r = 0.6. They found that 6.6%
with reading difficulties when they used
the criterion of being 2yr 4mth behind
chronological age in reading age.
• They produced 2 distinct groups
among this 6.6%. One group they
defined as “backward readers” with low
IQ and another group were called
“specific reading retarded (SRR)” who
were also poor readers, but by contrast
had reasonable IQ.
8
Characteristics of dyslexia
Isle of Wight study (Michael Rutter et
al., 1970; Rutter & Yule 1975)
By taking out the low IQ backward
readers from this 6.6% Rutter et al.
were left with 3.7% who were SSRs.
These were children who were at least
2 yr 4mth behind in their reading age,
but within the average range of IQ or
above average in IQ.
9
Characteristics of dyslexia
Isle of Wight study (Michael Rutter et
al., 1970; Rutter & Yule 1975)
• The frequencies of SSRs were plotted
against their reading scores. They
found a “hump” at the bottom of the
curve. There were more than would be
expected with very poor reading
scores.
• Both backward readers and SRRs had
a family history of problems in reading
and speech delay and current speech
problems. These problems were 3
times greater than the rest.
10
Characteristics of dyslexia
• Rutter and Yule did not think they’d identified “dyslexia”.
They did not see it as single disorder with a genetic
component. They noted great regional variations in the
incidence of SRR, suggesting an environmental incidence.
• Despite this, educators cite this study as evidence for
dyslexia.
• Some people would argue that there is not a biological
connection with dyslexia. However, there is a connection
between genetics and phonological processing weakness.
• There is a continuum of phonological weakness and not
all individuals who are weak have problems in reading.
They may well have had a good education to overcome
their potential reading difficulties.
11
Dyslexia: prognosis
• Can children with dyslexia eventually recover?
• Rayner et al. (1989) studied a professor (SJ) in the USA
who’d been classified as a developmental dyslexic. So
here’s one case showing that it’s possible to become a
fluent reader, and in this case to became a professor.
• Felton, Naylor and Wood (1990) studied 115 adults
who had their reading well-documented in childhood.
These made 3 groups:
37 were reading disabled in childhood,
38 had been borderline
40 had had no reading difficulties
(37 + 38 + 40 = 115).
12
Dyslexia: prognosis
As children
As adults
Reading
disabled
Border
Still RD
18
-
Border
10
9
Average
9
29
The table shows,
for example, that
18 children who
were reading
disabled (RD)
remained so
when adults; but
10 children who
were RD
became
borderline
readers when
adult, and 9 who
were RD actually
grew up to
become average
readers.
13
Dyslexia: prognosis
• As shown in the previous table, Felton et al.
demonstrated that of 37 who were RD in childhood, 19
(51%) left that category in adulthood. The situation is
even better for those children who were borderline as 29
out of 38 (76%) were fluent readers in adulthood.
• Felton et al. also found that nonword reading (e.g. blant,
gront) and manipulation of phonemes much worse for
adults who were still RD, even controlling for IQ and
SES. This suggests that these had problems with
phonology.
14
Dyslexia v. “garden variety”: worth the distinction?
• Both types have the same phonological deficits when
equalised on word recognition (Stanovich & Segal,
1994).
• Matching both types on chronological age rather than
reading, shows even greater similarity (Fletcher, et al.,
1994).
• There may be special cases, but there is substantial
evidence against dyslexia being a unique syndrome.
• Another problem is the use of IQ as a basis for calculating
“potential”. Many think of IQ as multidimensional rather
than unitary. The conventional IQ test may be too
narrow.
• Both types require the same kind of reading instruction.
And importantly, most or all children can learn to read
well with good instruction.
15
Reading comprehension
• There have been attempts to look at a listening
comprehension - reading achievement discrepancy. These
types of readers have small differences from conventional
readers (Fletcher et al, 1994).
• Another aspect of using an IQ basis is the child of high IQ,
who has a significant discrepancy between reading
performance and potential.
• However, in absolute terms reading may be below average.
In terms of teaching this child potentially has extra reading
instruction and resources over another child at the same
reading level, but with average or slightly below average IQ.
• But the absolute level of performance is an important
problem. If there are weaknesses in reading, spelling or
writing, so that a child is operating below a criterion level,
then that child needs to be taught these skills to the
appropriate level.
16
Summary so far
• There is controversy whether dyslexia is a special
condition in relation to other types of poor reader.
• A problem from the educational aspect is that it does not
define a group who need a distinctive educational
approach.
• The diagnosis may also be detrimental if it gives the
impression that this is a condition that cannot be cured.
It has to be said that it can also confer a sense of relief in
some that a concrete diagnosis has supposedly been
achieved.
17
Biological theories of dyslexia
Hormonal theory
Beech & Beauvois (2006) have proposed that prenatal
hormonal experience in the womb can affect phonology
(processing of sounds), which in turn affects reading.
Those who experience more testosterone (male
hormone) were found to perform worse in phonology and
in audition.
Genetic factors
There has been much work in this area examining the
inheritance of component reading skills. Also work on
finding gene markers on certain chromosomes.
Language areas
Positron emission tomography (PET) and functional
magnetic resonance imaging (fMRI) has been very useful
at developing our understanding of both processes and
18
structure in relation to dyslexia.
Biological theories of dyslexia
The cerebellum
This theory (Nicolson & Fawcett, 1990) suggests that
the cerebellum, which has control over automaticity
and dexterity could explain dyslexia. The
cerebellum influences the processing of speech and
motor control. For example, the estimation of time
and balance are connected with the cerebellum.
Connected with this, is the next theory:
19
Biological theories of dyslexia
Magnocellular/transient systems
Magnocellular theory was advocated by Stein
& Walsh (1997)
The magnocells—which are large neurones
in the brain—control the timing of sensory
and motor events. The connection with the
cerebellum is that the cerebellum processes
the magnocellular brain regions. Weakness
in the visual magnocellular system can
confuse letter order and lead to weak visual
memory. Similarly there could be an
analogous weakness in phonology. Many
concur that this system and its implications
for timing is important for accounting for
dyslexia.
20
Cognitive theories of dyslexia
Phonological processing
We’ll deal with this in more detail later. There has been a
lot of research on this with some suggesting that
phonological difficulties (processing the sounds in words)
are the main cause of dyslexia. But it is probably not this
simple. There is a dominant view (esp. University of
York) that phonology is very important.
21
Cognitive theories of dyslexia
Temporal (timing) problems
This can be closely connected to phonology problems as if
there are problems in timing, then processing sounds is
going to be difficult. Similarly, information entering the
retina has to be processed rapidly and problems in
timing can also be detrimental to visual processing.
Visual problems
There have been different kinds of theories, including
problems with binocular vision and problems with
forming stable fixations. There could also be confusions
in letter order (e.g. girl read as ‘grill’).
22
Cognitive theories of dyslexia
Working memory
This retains information for a brief time while it is being
processed and perhaps transferred into long term
memory. Weak working memory may help to explain
dyslexia.
Automaticity
We’ve already seen this in relation to the operation of the
cerebellum, which controls automaticity. Normally when
we learn a skill we become so good that we become
automatic. For example, when driving. Because those
with dyslexia don’t achieve automaticity, it means that they
are slowed down in their processing. They may, however,
achieve automaticity eventually—it just takes much longer.
23
Summary on developmental dyslexia
• Developmental dyslexia is considered to be a condition in
which reading (and spelling) is not progressing at the same
pace as other intellectual areas. Testing involves identifying
cut-off points to identify the condition. But, getting a clearer
cut-off means waiting longer, which also means remediation
may be just slightly more difficult.
• There is controversy concerning the status of dyslexia,
particularly as identifying the condition does not necessarily
lead to a way forward for remediation.
• The biological factors related to dyslexia are: hormonal,
genetic, the language areas, the cerebellum, magnocellular
systems.
• The cognitive factors are not unrelated to the biological
ones: phonology, timing, automaticity, visual and working24
memory.