Cognitive theories of dyslexia

Question 1

What does the phonological deficit hypothesis say that dyslexia is characterised by?

Answer 1

Impaired representation (storage/retrieval) of sounds in speech; impaired phonological awareness; poor verbal STM and slow naming speed (phonological deficit)

Question 2

Where did the phonological deficit hypothesis come from? (citations)

Answer 2

Dyslexia is on a continuum with normal reading; difficulties were present across cultures, languages and education, and the need to learn g-p correspondences varies across languages. Simply, phonological awareness influences reading progress and vice versa. (Bradley and Bryant, 1983; Bruck, 1992; Share, 1995)

Question 3

What are some questions within the phonological deficit hypothesis?

Answer 3

What is the age of development of each PA skill? How should PA be tested? Is PA independent of IQ or vocabulary?

Question 4

What are some problems with the phonological hypothesis?

Answer 4

What is the direction of causality? Are well controlled training studies adequate tests? Is there an underlying biological or cognitive cause?

Question 5

What are the educational implications of phonological deficits?

Answer 5

Mild PA deficit: delayed development.
Severe PA deficit: rely on context for decoding.
Effortful decoding means needed more time for reading comprehension. Can teach phoneme awareness and g-p conversions. Early identification and intervention through schools is helpful (Wise et al., 1990)

Question 6

Castles and Coltheart (2004)

Answer 6

PA plays a causal role in dyslexia as it is seen across languages and cultures, but no studies reviewed have found reliable results that show that the causal link exists. Argue that this reflects that once children acquire reading and spelling skills, they change the way in which they perform phonological awareness tasks, using their orthographic skills either in addition to or instead of phonological skills. This means that methodologies and measurements should reflect this and control for pre-existing literacy skills.

Question 7

Hulme et al. (2005)

Answer 7

Commentary on Castles & Coltheart

• Claimed Castles & Colthearts view was ‘overly narrow’ and criticised their methodological rules
• PA (phonological awareness) was important in learning to read
• PA training with letter-sound knowledge had limited but reliable effect on later reading.
• Orthographics are used to solve PA tasks according to Castles & Coltheart, but this paper argues this is only relevant to shallow languages such as Hebrew
• Moderator and mediator effects from other language skills may affect the role of PA.

Question 8

Ziegler et al. (2003)

Answer 8

Most of the research occurs in English-speaking countries (need to assess the generalisability of the core findings)
Studying German and English speaking children: more similarities than differences in the deficits associated with dyslexia
Dyslexic individuals across cultures exhibited a reading speed deficit, a nonword reading deficit and a slow and serial phonological decoding mechanism
If a phonological deficit is core to dyslexia, it should be universal and present in all children, regardless of their native language. This appears to be the case.
Replicate Landerl et al (1997) but with better methodology - they found English showed much more severe deficits in word and nonword reading

Question 9

Bus & van Ijzendoorn (1999)

Answer 9

A meta analysis, large sample, A training of phonological awareness improves children’s phonological awareness as well as their reading skills but to a lesser extent. They found phonological awareness explained about 12% of the variance in word-identification skills. Preschoolers tend to profit more from phonological training than participants from kindergarten or primary school. children from special groups did not seem to profit more from phonological training than “normal” children whom we expected to reach their maximum performance earlier.
PA is an important but not sufficient condition for learning to read (partial support).

Question 10

Paulesu et al. (2001)

Answer 10

The recognition of dyslexia as a neurodevelopmental disorder has been hampered by the belief that it is not a specific diagnostic entity because it has variable and culture-specific manifestations. In line with this belief, we found that Italian dyslexics, using a shallow orthography which facilitates reading, performed better on reading tasks than did English and French dyslexics. However, all dyslexics were equally impaired relative to their controls on reading and phonological tasks. Positron emission tomography scans during explicit and implicit reading showed the same reduced activity in a region of the left hemisphere in dyslexics from all three countries, with the maximum peak in the middle temporal gyrus and additional peaks in the inferior and superior temporal gyri and middle occipital gyrus. We conclude that there is a universal neurocognitive basis for dyslexia and that differences in reading performance among dyslexics of different countries are due to different orthographies.

Question 11

What is the double deficit hypothesis?

Answer 11

An extension of the double deficit hypothesis where dyslexic people have 2 independant sources of dysfunction- phonological processing (accuracy) and naming speed (fluency). Predicts an addictive effect of PA and naming speed deficits on reading.

Question 12

Wolf and Bowers (1999)

Answer 12

Modest correlations between PA and naming speed, with different contributions to word identification skill from each. Used rapid automised naming tasks.

Question 13

What are the implications of slow naming speed and phonological processing problems?

Answer 13

Prevents connections between graphemes and phonemes occurring, limits the quality of representations in memory, increased practice is required to learn the orthographic code.

Question 14

Badian (1997)

Answer 14

Testing double deficit hypothesis with dyslexic children and controls as well as adding orthographic skills. Most of the dyslexic children had double or triple deficits, suggesting that it’s a combination. More research is needed to test if the third factor is a product of one of the 2 or its own factor.

Compares dyslexic readers to garden variety, those with low verbal IQ(high reading scores), and younger reading-level matched. 99 children overall.

Used phonological measures such as non-word reading test and phoneme deletion task. Tested naming speed (rapid automatized naming task); orthographic skills (Jordan Left-right reversal test); and verbal intelligence.

All dyslexic children had at least one deficit but 68% had 2 deficits; dyslexia is not solely based on having both deficits- potentially just adds to severity.

Question 15

Lovett et al. (2000)

Answer 15

Compares 166 children with phonological awareness deficits (22%), visual naming-speed deficits (24%) and those with both deficits (54%).

Those with double-deficits performed worse in tests than those with just one.
VNS group is specifically impaired in word identification and accuracy but better at letter-cluster sounds.

35 hours of interventions (4 x 60 minute sessions per week) - one of: Word Identification Strategy Training (WIST), Phonological Analysis & Blending/Direct Instruction (PHAB/DI) or Classroom Survival Skills Program (CSS, control condition). Found all children improved after interventions.

Either deficit can lead to dyslexia but those children with both deficits together will have more severe dyslexia.

Deficits in visual naming speed disrupt reading acquisition by inhibiting growth in the connections between phonemic and orthographic patterns.

54% of their sample had both deficits - how separate are the two?
Interventions improve all the groups - so how specific are the deficits?
Doesn’t find strong proof - why not stick to phonological deficit hypothesis? Is VNS influenced by PA rather than being a distinct, separate deficit?

Question 16

McBride, Chang & Manis (1996)

Answer 16

Poor readers (at or below the 25th percentile on the WRAT Wide Range Achievement Test Revised) speeded naming + phonological awareness sig associated. Word reading, verbal intelligence no association.
·       Good readers (at or above the 50th percentile on the WRAT) PA + verbal intelligence sig associated. word reading, naming speed not.
·       Evidence for differential associations naming speed + PA w word reading for good + poor readers

8 years 3 months - 10 years 5 months

86 White, 19 Asian, 12 African American, 5 Hispanic, and 3 East Indian (but didn’t analyse specifically within those who may be bilingual)

(None with reading disorders)

Support DD hyp as found evidence for differential associations in naming speed + PA for word reading for good + poor readers.

Question 17

Schatschneider et al. (2002)

Answer 17

Key message of abstract = PA and double deficits combined will cause more of a deficit (this is widely accepted)
Demonstrated that greater severity of reading impairment is found in those with a double-deficit
However, these results may have been found due methodological issues
Due to statistical artifact from grouping children and on their performance of two correlated continuous variables
This artefact makes it difficult to establish the impact of deficits in naming speed on reading ability independent of deficits in PA
When the relationship between naming speed and PA was investigated, they found a positive correlation which means that those in the double-deficit group will have a lower PA skill than those in the single phonological deficit group - which means that you can’t isolate the effects of naming speed
There is also a curvilinear relationship between phonological awareness and reading skills meaning lower PA skills have a larger impact on reading ability.

Does not support DD hyp: A lack of sufficient evidence which isn’t based on the grouping of children based on performance of the two correlated continuous variables
Not enough evidence that naming speed exists independently, current evidence has found that both PA and naming speed are highly correlated.

Question 18

What is automatization theory?

Answer 18

A sensory theory where impaired ability to automatise in dyslexia and dysfunctional motor control affects articulation with knock on effects for phonological reps and learning of grapheme-to-phoneme correspondence rules.
Nicolson and Fawcett- brain basis: cerebellar deficit hypothesis.

Question 19

Where is automaticity most effected in dyslexic people?

Answer 19

In dual tasks e.g. counting and balancing. In single tasks dyslexics can learn to compensate.

Question 20

Nicolson & Fawcett (1990); Nicolson, Fawcett and Dean (1995)

Answer 20

Tested cerebellar function using behavioural tasks: Balance, coordination and time estimation was impaired in 40-100% of cases with dyslexia.

Question 21

What skills does impaired automatisation effect?

Answer 21

Articulation, acquiring visual word forms, reading, learning associations between sounds and letters, motor control and other learning tasks.

Question 22

van Daal & van der Leij (1999); Wimmer et al (1998)

Answer 22

Mixed replication of findings of automatisation theory.

Question 23

What are problems with automatisation theory? (Savage, 2004)

Answer 23

Replication of findings has mixed results, potential overlap with symptoms of comorbid disorders, the theory is not very specific, the quality of research conducted in this area is varied, reading and motor skill are not linearly related (like PA and reading), the theory is circular as you can’t learn to be automatic but practice helps.

Question 24

What are the educational implications of automatisation theory?

Answer 24

Children can adapt to impaired automatisation but may find dual-taks difficult and will need additional time to develop automaticity across skills. Training in reading may not improve motor skills.

Question 25

Nicolson and Fawcett (1990)

Answer 25

Supports Conscious Compensation Hypothesis, which suggests that dyslexic children can attain equivalent performance to normal on a wide range of tasks, but they do so by “working harder”.
Partially supports the Dyslexic Automatization Deficit (DAD), but realises that this isn’t the only possible interpretation of the results.
Attentional allocation deficit is another possible interpretation.
Dyslexic children could perform tasks as well as normal, in isolation, (balance task), but showed sig impairment when under dual-task conditions.
The results found would be hard to describe using reading-specific theories. So, future research should look at general skill acquisition.

Question 26

Wimmer (1999) & Rayberger & Wimmer (2003)

Answer 26

Both believe that there is more to the Automatization Theory, as there was failure in replicating balancing task
Found poor balancing is not associated with Reading Difficulty (RD) but with ADHD children
Poor performance of Rapid Naming tasks is not associated with ADHD but with RD children
Believe the original study (Nicolson) did not test solely children with dyslexia - they included those with ADHD which changes the results
Wimmer 2003 - suggests that only the automatization of processes connecting vision with language may pose a problem for dyslexic children (this is due to a specific cerebellar dysfunction)

Question 27

Rochelle & Talcott (1998)

Answer 27

Meta analysis working out the connection between balance problems and dyslexia
Aimed to study the magnitude/consistency of balance difficulties in dyslexia populations and what sampling/stimulus characteristics modulate the strength of effects gained for measure of balance across studies
Comparisons between dyslexic populations and non-dyslexic populations
Selection criteria: 17 studies, 15 for statistical analysis. 9 studies with 70 separate dependent measures measures of effect size
Found balance deficits are associated with dyslexia, but this was connected to third variables such as co-morbid ADHD and low IQ, as opposed to reading ability

Question 28

Ramus (2003)

Answer 28

Aim: to investigate whether cerebellum dysfunction is a cause for motor deficit in dyslexia.
Ramus et al tested this through phonological and motor skill tests.
They assured testing for the cerebellum through motor skill tests and time estimation tests. If all these tests were impaired, this would imply that there is a dysfunction in the cerebellum.
Findings were that, there were general motor skills in those with dyslexia. However, this could be due to co-morbid disorders such as ADHD or DCD.
No significant impairments were found for time estimation, therefore, this study refutes the idea that the cerebellum is impaired in individuals with Dyslexia.
Any significant findings for impairments for motor skills were also not significantly correlated with phonological/reading abilities and therefore, the Cerebellar theory is refuted.

Question 29

What is the amplitude modulation hypothesis?

Answer 29

Is a sensory theory that children and adults with dyslexia have trouble discriminating between different amplitude envelope (rise-time) patterns in voices. These patterns are thought to be important in early life in detecting speech rhythm and prosody. (Goswami)

Question 30

What type of speech was intelligible to dyslexic participants in Goswami’s study?

Answer 30

Speech with only slow temporal modulations

Question 31

What is amplitude envelope and what is its function?

Answer 31

refers to the changes in the amplitude of a sound over time a.k.a rise time. It is important in speech for syllable segmentation.

Question 32

Goswami and Thomson (2002)

Answer 32

Impairment in identifying modulation frequencies which are important in subsyllabic (phoneme/ onset-rime) elements of speech in dyslexics.

Question 33

Goswami (2011)

Answer 33

Phase locking of neurons to temporal aspects of speech (only respond to specific aspects of speech). The core deficit in dyslexia is phonological. Temporal sampling of speech by neuroelectric oscillations that encode incoming information at different frequencies could explain the perceptual and phonological difficulties with syllables, rhymes and phonemes found in individuals with dyslexia.

Question 34

What does the amplitude modulation hypothesis predict about development?

Answer 34

Exposure to sound changes begins in early life in the womb. Acoustic cues to rhythm of language important to phonological development. Amplitude modulations in the 2Hz range are important for child directed speech and are impaired in dyslexia. Amplitude modulation detection is also useful for identifying larger grain-size segments used by pre-readers. Print-sound correspondences are important once a child starts to read.

Question 35

Vanvooren (2017)

Answer 35

Longitudinal study of pre-readers at risk of developing dyslexia later in life.
Found that there was no effect of family risk on pre-reading auditory skills & speech perception, but that their skills (especially amplitude envelope processing) in kindergarten were related to later phonological processing and literacy.
Links are found with the auditory processing of cues characteristic for the temporal speech amplitude envelope, rather than with other auditory cues important for speech intelligibility

Provides behavioral support for the link between pre-reading speech amplitude envelope processing and speech perception for future phonology and reading

Question 36

Goswami, Huss et al. (2013)

Answer 36

First longitudinal study to assess rhythmic musical processing as a predictor of individual differences in word reading, comprehension and non-word reading.
It was an important independent longitudinal and concurrent predictor of variance in reading attainment in children.
Partially supports - a year on children with dyslexia had fallen behind younger RL controls in rise time sensitivity and performance on musical tasks.
But they were not statistically behind younger RL controls in reading or phonological tasks.

Question 37

Bhide et al (2013)

Answer 37

Those with dyslexia and other reading difficulties seem to display impaired auditory rhythm perception and difficulty with musical beat perception tasks. This is important to note, due to the fact that knowing what dyslexia affects can help us to treat and improve it. For example, in this case, musical interventions with poor readers may improve their rhythm perception and simultaneously lead to greater reading and phonological skill. Therefore, the paper aimed to establish whether the musical intervention leads to benefits comparable with phoneme-grapheme interventions.

Musical training (training perceptual and cognitive skills that underpin poor phonological development) is as effective as direct (computer based) training. This direct training has already been proven to be an effective intervention. Various musical training was used, for example, tapping along to a metronome

Supports - theory claims children have deficits in discriminating rise time and rhythm, study showed musical intervention improved phonological performance of dyslexics. So, there is support for the foundations of the theory.

The musical intervention trains the rhythmic perception and rhythmic entrainment skills that are important for the development of phonological awareness. As the musical intervention was effective, this shows support for this hypothesis