Reading difficulties

Question 1

what are reading difficulties?

Answer 1

• encompasses range of diagnoses & cog/beh profiles
• dyslexia
• DLD
• poor comprehenders
• other reading difficulties or deficits

Question 2

dyslexia

Answer 2

• learning difficulty affecting skills involved in accurate & fluent word reading, and spelling (British Dyslexia Association, 2009)
• associated with a range of difficulties (Bedias et al., 2013) e.g. speed of word processing & these are broad at cog level

Question 3

who has dyslexia

Answer 3

• 9-12% of population (European Dyslexia Association)
• sim prevalence across ranges of IQ & SES: isn’t associated with social circumstance or general IQ
• more frequent in males - might be due to more variance in reading behs of males (Arnett et al., 2017) or that females better at masking symptoms possibly

Question 4

multi deficit model level of analysis

pennington (2006)

Answer 4

1. aetilogical risk & protective factors
2. neural systems = biological expression e.g. brain structure, comm between diff neural systems
3. cog processes
4. behavioural expression/disorders (also comorbidity & variability between disorders)

Question 5

pennington (2006)

further reading

Answer 5

• need for a measure deficit model arises partly from advances in understanding the complex genetics of behaviourally defined developmental disorders like dyslexia, ASD, ADHD
• emerging etiological model for developmental disorders e.g. dyslexia, is probabilistic & multifactorial
• prevailing cognitive model has been deterministic & often focused on a single cognitive cause e.g. phonological deficit as the cause of dyslexia
• potential contradiction in our explanatory frameworks for understanding developmental disorders
• resolve contradiction by presenting a multiple cognitive deficit model of developmental disorder

Question 6

genetic basis of dyslexia?

multi deficit model

Answer 6

• reading abilities appear to be heritable
• ~40-60% (Raskind et al., 2013)
• child at greater risk if parents have dyslexia (Schuite-Korne et al., 1996)

Question 7

stevenson et al. (1987)

genetic basis of dyslexia?

Answer 7

• studied 285 twin pairs
• heritability 29% for reading abilities
• 73% spelling abilities

all once intelligence was controlled for

Question 8

examples of candidate genes of dyslexia

Answer 8

• KIAA0319
• DCDC2
• DYX1C1
• ROBO1
• FOXP2

Question 9

KIAA0319 on chromosome 6p

candidate genes for dyslexia

Answer 9

• affects neural migration & radial glia adhesion - specialised cells involved in dev of nervous system
• v from genetic pooling of 223 ppts with DD (dyslexia) & 273 controls
• explanation of dyslexia at genetic level

(Cope et al., 2005)

Question 10

DCDC2 in DYX2 locus

candidate genes for dyslexia

Answer 10

• particularly associated with severe phenotype of dyslexia (Schumacher et al., 2006)
• longitudinal study found that genetic risk from DCDC2 strengthens the link between pre-reading maze learning & subsequent reading impairment (Gabel et al., 2021)
• this gene responsible for skills involved in finding a way around a maze but also reading showing particular skills helpful for learning to read

Question 11

pleiotropy

Answer 11

• one gene many effects
• not one-to-one mapping
• not on/off
• gene has multiple effects across multiple domains

Question 12

polygenicity

Answer 12

many genes contribute to a single trait

Question 13

generalist genes hypothesis

plomin & kovas (2005)

Answer 13

• genes for LD are same as those for normal variance
• genes for symptom A are same as those for symptom B
• genes for one LD are same for another LD e.g. dyslexia & ADHD

Question 14

how do genes influence dyslexia?

Answer 14

• high rates of comorbidity with other types of neurodiversity & psychiatric disorders
• genome-wide association study found associations between dyslexia risk & risk for ADHD, bipolar disorders & SZ (Gialluisi et al., 2021)
• genes interact with environment: higher influence when SES is high (Friend et al., 2008) in the expression of dyslexia

Question 15

dilnot et al. (2017)

Answer 15

• investigated risk factors for predicting att, beh & reading readiness in 251 children at risk of dyslexia (parent has dyslexia)
• home literacy env & child’s health predicted reading readiness
• home literacy env & family stresses predicted att & beh
• no main effect of family risk once environmental factors controlled for so heritability no longer predicting factor

Question 16

cog theories for dyslexia

Answer 16

• phonological deficit theory
• automisation hypothesis
• double-deficit theory
• magnocellular deficit theory

Question 17

phonological deficit theory

Answer 17

• deficit in phonological awareness
• e.g. ability to recognise spoken parts of sentences & words
• sounds same, rhyme patterns, repeated sounds (sc,sk), ability to segment between words, syllabic breakdown of words

Question 18

swan & goswami (1997)

phonological deficit theory

Answer 18

• groups: dyslexia, ‘poor readers’, CA control with typical reading ability, reading age MA (younger children)
• measured picture naming & phonological abilities
• picture naming: children with dyslexia poorer performance
• children with dyslexia performed similarity to reading-age controls for syllable & onset-rime measures
• children with dyslexia had poorer performance than reading-age controls for phonemic tasks
• both children with dyslexia & poor readers had better performance for high frequency words on the phoneme tasks

Question 19

automisation hypothesis

Answer 19

• dyslexia is as result of a deficit in automatic processing
• e.g. difficulty ‘automising’ reading behs once learnt
• might be caused by reduced activation in cerebellum

Question 20

moores et al. (2003)

automisation hypothesis

Answer 20

• ppl with dyslexia & controls took part in tasks that required focusing & shifting att between 2 target types (shapes and colours)
• dyslexia & control performance was sim for focusing att
• but dyslexia performed sig worse when relied on shifting att
• recog doesn’t appear to be automatic
• 2 hypotheses from this study - general resource deficit, automisation deficit

Question 21

general resource deficit

automisation hypothesis

Answer 21

inds with dyslexia lack the resources to perform well on the att-shifting task

Question 22

automisation deficit

automisation hypothesis

Answer 22

inds with dyslexia struggle to automise some skills, & therefore need more resources for these particular skills

Question 23

moores et al. (2003) investigating general resource deficit and automisation deficit

Answer 23

• normal & degraded stim (shapes)
• will increasing attentional load disproportionally affect the dyslexia group?
• dyslexia group weren’t uniquely affected by degraded stim
• suggests a general lack of resources doesnt explain performance diffs
• could be explained by an automisation deficit

Question 24

double-deficit theory

badain (1997)

Answer 24

• phonological awareness
• rapid naming
• 3rd orthographic deficit?

Question 25

single deficit models

Answer 25

* 1 to 1 relationship between bio factors or cog deficits & presentation of the disorder * e.g. trying to find a singular 'core' explanation for dyslexia that fits every diagnosis

Question 26

multiple deficit models

Answer 26

* complex etiology * shared & independent factors contributing to a cog skill * genes have a probablistic influence (not on/off) * pennington & bishop (2009)

Question 27

explanations of comorbidity

Answer 27

* one diagnosis increases likelihood of receiving another diagnosis * shared liabilities - could have a genetic, cog, or cellular basis * correlated liabilities - associated but distinct risk factors

Question 28

comorbidity within dyslexia

Answer 28

* DLD (Catts et al., 2005) * ADHD (Gilger et al., 1992) * developmental dyscalculia (Landerl & Moll, 2010) * developmental coordination disorder (Kaplan et al., 1988)

Question 29

snowling et al. (2019)

Answer 29

* family risk of dyslexia or DLD vs TD controls * observed before entering school (t1,t2) & during school (t3-5) * measured range of cog predictors * classified in year 3 of school into disorder groups * severity changes over time * poor lang as preschool precursor of deficits * dyslexia & DLD show diff dev trajectories * more severe phonological deficits in comorbid cases * motor & EF deficits as a marker of wider neural deficits (corr but unrelated to lang performance) * improvements in lang dev in comorbid group could be protective * very important to examine influence of time on outcomes

Question 30

why does comorbidity occur between dyslexia & other neurodev disorders?

Answer 30

* shared genetic etiology * shared cog bases * ev points towards sim underlying mechanisms rather than causality (van Bergen, 2023)

Question 31

evidence based interventions

Answer 31

* theory of how a skill develops * theory of how a skill is promoted * high quality evidence | snowling & hulme (2011)

Question 32

theory-based interventions

Answer 32

* theories inform which skills are targeted by the intervention * e.g.: * phonological deficit theory identifies phonemic awareness as a key skill * intervention based on isolating, identifying & blending phonemes

Question 33

review of phonologival awareness training

Answer 33

* effect sizes reported by the national reading panel (NICHD, 2000) * 0.86 on phonological awareness * 0.53 on reading outcomes * 0.59 on spelling outcomes * highly effective across literacy domains * not effective outside domain e.g. maths * improved in combination with letter knowledge intervention

Question 34

theory of how a skill develops

Answer 34

* ev reviewed to see how a skill is best promoted * e.g. phonics instruction can be used to improve letter-sound knowledge * different techniques: synthetic phonics, analytic phonics * both focus on segmenting & understanding words but do this in different ways * both techniques useful, but combined approach with synthetic phonics instruction appears most successful

Question 35

high quality evidence

Answer 35

* rigorous trials * educationally realistic trials - able to implement them, reflect types of behs appropriate to classroom & ind * randomised controlled trials * scaled up classroom research - approaching interventions which are realistic to which they would be implemented and that which would be most helpful

Question 36

things to consider

Answer 36

* cost of intervention - realistic and affordable * implementing into educational settings - e.g. how long does it take? * accommodating for inds with reading difficulties if interventions aren't successful - relates to variability in behavioural phenotype of dyslexia, comorbidity. What are the other options?

Question 37

snowling & hulme (2011) ## Footnote further reading

Answer 37

* decoding difficulties appear to be caused by problems with phonological (speech sound) processing * any well-founded educational intervention must be based on a sound theory of the causes of a particular form of learning difficulty, which in turn must be based on an understanding of how a given skill is learned by TD children * phonologically based interventions are effective in ameliorating children's word level decoding difficulties * smaller evidence base showing that reading & oral language (OL) comprehension difficulties can be ameliorated by suitable interventions to boost vocabulary and broader OL skills