Cognitive theories of dyslexia Flashcards
(37 cards)
What does the phonological deficit hypothesis say that dyslexia is characterised by?
Impaired representation (storage/retrieval) of sounds in speech; impaired phonological awareness; poor verbal STM and slow naming speed (phonological deficit)
Where did the phonological deficit hypothesis come from? (citations)
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)
What are some questions within the phonological deficit hypothesis?
What is the age of development of each PA skill? How should PA be tested? Is PA independent of IQ or vocabulary?
What are some problems with the phonological hypothesis?
What is the direction of causality? Are well controlled training studies adequate tests? Is there an underlying biological or cognitive cause?
What are the educational implications of phonological deficits?
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)
Castles and Coltheart (2004)
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.
Hulme et al. (2005)
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.
Ziegler et al. (2003)
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
Bus & van Ijzendoorn (1999)
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).
Paulesu et al. (2001)
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.
What is the double deficit hypothesis?
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.
Wolf and Bowers (1999)
Modest correlations between PA and naming speed, with different contributions to word identification skill from each. Used rapid automised naming tasks.
What are the implications of slow naming speed and phonological processing problems?
Prevents connections between graphemes and phonemes occurring, limits the quality of representations in memory, increased practice is required to learn the orthographic code.
Badian (1997)
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.
Lovett et al. (2000)
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?
McBride, Chang & Manis (1996)
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.
Schatschneider et al. (2002)
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.
What is automatization theory?
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.
Where is automaticity most effected in dyslexic people?
In dual tasks e.g. counting and balancing. In single tasks dyslexics can learn to compensate.
Nicolson & Fawcett (1990); Nicolson, Fawcett and Dean (1995)
Tested cerebellar function using behavioural tasks: Balance, coordination and time estimation was impaired in 40-100% of cases with dyslexia.
What skills does impaired automatisation effect?
Articulation, acquiring visual word forms, reading, learning associations between sounds and letters, motor control and other learning tasks.
van Daal & van der Leij (1999); Wimmer et al (1998)
Mixed replication of findings of automatisation theory.
What are problems with automatisation theory? (Savage, 2004)
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.
What are the educational implications of automatisation theory?
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.
