Week 5: Dyslexia Flashcards
(27 cards)
cost of low literacy
- Average 18-year-old with “very poor” literacy skills will earn around £33K less during their working life than a person with a basic level of literacy
- About 7 million people in the UK have “very poor” literacy skills (i.e., very poor vocabulary and cannot read lengthy text on unfamiliar topics) National Literacy Trust (2021)
- Low literacy can be a consequence of dyslexia
how does literacy link to dyslexia?
Affects ability to read single words.
Ability to understand the meaning of the text is not directly impacted by dyslexia, however may make it harder if the basic processes are affected.
Pre-history of research on reading problems
- Early research by Adolph Kussmaul introducing term Word blindness attributing the origins of reading problems to visual deficits
- Rudolph Berlin introducing term Dyslexia – from Greek disordered words
- General idea of reading difficulties as an isolated deficit Kirby (2020)
Only about reading - Dejerine (1892), Pure alexia in Monsieur C
- 68-year-old man, who was considered highly intelligent and enjoyed excellent health until his cerebrovascular accident on the 25th of October 1887…
Bub et al. (1993)
Percy F.: the most famous description
Percy F. – a well-grown lad, aged 14 – is the eldest son of intelligent parents
[…]. He has always been a bright and intelligent boy, quick at games, and in no
way inferior to others of his age. His greatest difficulty has been – and is now–
his inability to learn to read. This inability is so remarkable, and so pronounced,
that I have no doubt it is due to some congenital defect […] the greatest efforts
have been made to teach him to read, but, in spite of this laborious and
persistent training, he can only with difficulty spell out words of one syllable […]
The schoolmaster who has taught him for some years says that he would be
the smartest lad in the school if the instruction were entirely oral […]
Description by William Pringle Morgan (1896, p. 1378)
Common characteristics of the early cases (in history)
- Smart
- Boys
- No deficit in vision
- High difficulty in learning to read
- … despite efforts put in teaching
- Potentially congenital
… and not so much changed…
* Independent from other skills (?)
* More prevalent among boys
* Not related to visual deficits
* Difficulty in learning to read
* Resistant against interventions
* Congenital (and heritable)
DEFINITIONS OF DYSLEXIA
Definitions II
Dyslexia is defined by difficulties with decoding, whereas by comparison comprehension is more intact. Peterson and Pennington (2012, p.1997)
Dyslexia in DSM-5
* It sits in the same place as Dyscalculia (i.e., specific learning disorder)
* The diagnostic considerations discussed in
Lecture 4 for Dyscalculia apply for Dyslexia as well
- Specifies impairment in reading, math and written expression
Prevalence
- Common cutoff for reading achievement is 1.5SD below population mean (has to be a cutoff somewhere within the normal distribution)
- This implies that about 7% individuals are diagnosed with dyslexia
– This 7% estimate comes directly from using 1.5SD cut-off! - Different authors propose different cut-offs so there are massive discrepancies in the prevalence estimates, typically somewhere between 5 and 10%(Peterson & Pennington, 2012; Roitsch & Watson, 2019)
- In each classroom it is very likely to have at least one child with dyslexia / meeting the criteria!
- This implies that about 7% individuals are diagnosed with dyslexia
- Children, who struggle with reading should be provided support even without / before formal diagnosis!
Stability of dyslexia
- Early onset
- Persists into adulthood
- Restricted progress in learning to read / spell out
- Do not catch-up spontaneously, not possible to remediate completely
Comorbidities
- Speech language disorders:
– Language impairment – problems in the development of structural language, including syntax (grammar) and semantics (vocabulary)
– Speech sound disorder – problems with accurate and intelligible production of sounds of one’s own language- Dyscalculia
- ADHD
Gender differences
- More often diagnosed in boys than in girls (1.5-3:1)
* In referred samples this difference is higher (3-6:1)- Probably boys with dyslexia are referred more often because of higher comorbidities including ADHD (i.e., they are more “problematic” when it comes to behavior)
Peterson and Pennington (2012) - Discuss: what are the consequences of that?○ Girls with dyslexia without comorbidity may be missed with intervention - harder to catch up
- Probably boys with dyslexia are referred more often because of higher comorbidities including ADHD (i.e., they are more “problematic” when it comes to behavior)
Dyslexia and other abilities
- Dyslexia occurs at all general ability levels
– Discrepancy criterion abandoned but still sometimes used in educational settings (e.g., in the US; Carr, 2023)- It is an isolated deficit
- It means that among people with dyslexia other abilities are normally distributed (as in the rest of the population)
(Peterson & Pennington, 2015)
Risk factors to dylexia: genetics
- Moderate heritability of both typical and non-typical reading
- Estimates similar across different samples
- Heritability changes with age:
– From .22 at age of six years
– To .82 at age of twelve years
Risk factors: gene - environment vs gene x environment
- Gene × Environment interaction:
– Heritability of dyslexia increases as parent education increases
– Home literacy environment gets more favorable and less variable, as parent education increases- Gene – Environment correlation:
– Passive: Home literacy environment dependent on parent’s genes
– Evocative: Family seeking to foster child’s interest
– Active: Child actively seeking environments matching their genotype Peterson and Pennington (2015)
- Gene – Environment correlation:
Risk factors: molecular genetics
- There are some candidate genes identified as related to dyslexia
- Effect of each of them is small, but they are offering new areas of investigation
Peterson and Pennington (2015)
- Effect of each of them is small, but they are offering new areas of investigation
Risk factors: Environment
- Low socioeconomic status (SES)
- SES accounts for about 10% of the variance in reading outcome
- In preschool years, individual differences in vocabulary and other literacy precursors are more influenced by family environment than by genes
Peterson and Pennington (2015)
Risk factor criticism:
- Definition too general to be helpful
– Not sufficient to distinguish from any other possible causes of reading failure- Potentially deficit is not selective
– This seem to be the case - Middle-class diagnosis
– Exploited by over-concerned and engaged parents for their children to get some advantage
– BUT: UK Disability Discrimination Act mandates support for all see Kirby (202
- Potentially deficit is not selective
Cognitive mechanisms: typical characteristics (Roitsch & Watson, 2019)
1 - phonological awareness and processing
2 - decoding nonsense/ unfamiliar words
3 - Reading single words in isolation
4 - innaccurate and labored oral reading
5 - lack of reading fluency
6 - names of letters and associated sounds
7 - learning to spell
8 - word finding and rapid naming
9 - aspects of written composition
10 - reading comprehension
Reading symptoms
- Effortful
- Numerous mistakes, often based on visual similarity of the words
– “witch” and “watch” hard to distinguish
- Numerous mistakes, often based on visual similarity of the words
Problems with writing
- Phoneme-to-grapheme-conversion is much more complex than grapheme-to-phoneme conversion (44 phonemes represented as 250 graphemes in English)
- Recall is more demanding than recognition
- Inconsistent spelling errors
– Phonetic errors e.g., bokly for broccoli
– Orthographic errors e.g., battelship
– Reversal errors e.g., b confused with d
Phonological theory
phonological problems (problems with processing sounds in oral language) lead to later problems processing written language
* Ability to attend to and manipulate linguistic sounds is crucial for the establishment and automatization of letter-sound correspondences, which underlie fluent word recognition through phonological coding
Multiple deficits account, Peterson and Pennington (2015)
- Phonological deficit, even if important, is neither sufficient nor necessary for dyslexia to develop:
– Phonological awareness
– Rapid serial naming
– Verbal short-term memory
– Vocabulary- The most powerful individual predictor varies with developmental stage:
– toddlers and young children, broader language development
– age 4 or 5 years, phonological awareness is the dominant predictor;
– tasks emphasizing speed (i.e., rapid serial naming and processing speed) become increasingly important as literacy development progresses, probably because they are more linked to reading fluency than to single- word reading accuracy
Peterson and Pennington (2015)
- The most powerful individual predictor varies with developmental stage:
Visual crowding: RAN activity
Prepare a stopwatch and try to name the objects on the slide as fast as possible. (rows of images)
Visual crowding
* Even though most studies focus on phonological problems, there is some evidence that visual crowding may contribute to reading problems in individuals with dyslexia
* Problem not at the “eye” level but at the visual processing level
Zorzi et al. (2012)
visual crowding
- The visual crowding affects pseudo-words reading more, which may indicate it is affecting the phonological processing
- Visual crowding affects reading also in adults, including individuals without dyslexia
- It is not about letters overlapping with each other, just about being very close one to another
Montani et al. (2015)
TREATMENT AND INTERVENTITON Peterson and Pennington (2015)
- Explicit instruction in:
– phonological awareness (ability to attend to and manipulate sounds in words)
– the alphabetic principle (understanding that words are composed of letters that represent sounds in a systematic fashion)
– phonics (matching sounds of spoken English with individual letters or groups of letters)
– word analysis
– reading fluency
– reading comprehension - The earlier it starts the better
- More efficient if provided in a one-to-one setting
- Phonics instruction particularly helpful
- Training of phoneme awareness
- Supported reading of increasingly difficult text, writing, comprehension strategies
(for visual crowing - extra space between words help with reading, Zorzi et al. 2012)
