Reading models and dyslexia

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Reading models and dyslexia

• Lorna Bourke

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Aims

• To understand the context of reading development
• To gain an awareness of acquired dyslexia in its
  different forms
• To gain understanding and knowledge of acquired
  dyslexia in terms of models of normal reading
• To be introduced to neuropsychological case
  studies that have advanced the study of acquired
  dyslexia
• To develop knowledge of the assessment battery
  typically used by Educational Psychologists to
  diagnose developmental phonological dyslexia

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Reading
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The need for written communication

• The invention of writing around 4000 B.C. was an
  important turning point in civilisation
• It allowed humans to communicate ideas across
  space and time
• Early writing took form of pictographs (drawings
  of objects)
• Most cultures developed symbols based on sounds,
  then able to spell out concepts that could not be
  easily pictured.
• Most languages use an Alphabetic writing system

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How do we learn to read?

• Reading is an artificial activity. It is a skill
  that must be taught to us.
• Reading is a complex perceptual task which
  involves scanning text, perceiving and
  understanding symbols and sounding out these
  symbols.
• Spoken language is a necessary precondition for a
  reading writing system.
• Even deaf children "read a spoken language, not
  a sign" Perfetti Sandak (2000)

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Friths Stages of Reading

• Frith (1985) proposed a set of stages of reading
  development.
• Children progress through these stages, and can
  be in more than one stage at the same time.
• Three stages are
• (1) Logographic
• (2) Alphabetic
• (3) Orthographic

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Logographic reading

• Logographic reading is based upon the visual form
  of a word.
• A child starting to learn how to read links the
  visual form with a sound and/or meaning.
• This stage relies heavily upon visual acuity.
• The words that a child can read based upon their
  shape is called the child's "sight vocabulary".

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Logographic reading

• The "sight vocabulary" is not perfect. Mistakes
  are frequently made with visually similar words
• Reading in a purely logographic way is not an
  optimal strategy.
• The sight vocabulary is limited by visual acuity,
  and each word must be learned independently, e.g.
  walk and walked.

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Alphabetic reading

• Frith's next stage of reading development is
  based upon grapheme-phoneme correspondence.
  (GPC)
• Grapheme is the term for a letter shape
• Phoneme refers to a unit of sound.
• In some languages this correspondence is
  straightforward (transparent) and/or
  rule-governed.
• When reading children sound the word out
• E.g. kitten is read k-I-t-t-e-n.
• Our ability to pronounce nonsense words depends
  upon knowledge of the relation between letters
  and sounds, e.g. baticks

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Alphabetic reading

• Some words have irregular spelling-
  pronunciations which are too complicated for the
  straightforward rules of GPC
• E.g. pint does not rhyme with hint or mint or
  lint.
• Plough, cough, or ought
• But it is possible for a child to be in two
  stages at the same time.
• In Frith's model this is key to reading
  development.
• The first two stages therefore support each other

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Orthographic reading

• Frith's final stage of reading development
• Characteristic of the adult, mature reader.
• Orthographic reading is evidenced by less
  reliance on grapheme-phoneme conversion and more
  'whole word' reading.
• An interaction between more basic reading skills
  (such as logographic strategies), linguistic
  knowledge and other cognitive processes.

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Mechanics of reading

• Eye Movements
• When we scan a scene or text, our eyes make rapid
  jerks called
• Saccades
• The study of saccades is possible with the use of
  an eye-tracker.
• This keeps track of the gaze by focusing on and
  monitoring the pupil while the participant reads.

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Recording eye movements during reading
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Eye tracking in progress
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Scanning Text

• Saccades 10-20 msecs
• Fixations
• pause for 250 ms
• perception occurs here
• The perceptual span
• (3/4 to the left, 15 to the right)

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How many Fs?

• Read the following Just ONCE! 
• FINISHED FILES ARE THE RESULT OF YEARS OF
  SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF
  YEARS.

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How many did you count?

• 2
• 3
• 4
• 6
• Most people count 3, but theres 6!!
• One reason you may have missed counting all Six
  is your brain does not process the "F" in "OF".

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What do we fixate on?

• 20 of function words
• 80 content words
• Just Carpenter (1980)
• Sometimes skip function words
• I love Paris in the
• the Springtime
• Rare words
• Shocking/unexpected words

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Reading in adults Dual-Route Model of Reading

• Two theories
• Speech recoding or Assembled Route
• Once recognised, the word is translated into an
  articulatory-acoustic code (GPC)
• Visual access or Addressed Route
• identified as a whole looked up from our
• Lexicon (an internal word pool)

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Evidence for Speech recoding

• Electromyographic recording.
• Recording throat movements to see if any movement
  occurs during reading, which could indicate
  acoustic coding because the voice-box would seem
  to be in use.
• The evidence is consistent with speech recoding.
• However, the evidence is indirect, and leaves
  several questions unanswered such as are those
  movements necessary? Do they help or hinder
  reading?

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Lexical decision times.

• Recording the time it takes to read words
  presented via computer screen.
• Homophones are used in these studies (e.g., plain
  plane), as well as non-word homophones (e.g.,
  brane).
• Phonemic similarity has been found to increase
  decision times, so people are slower to respond
  "Non- word" to "brane" than to "nokim"
• Such results suggest that it is the phonemic
  similarity that is causing the delay.
• These delays are called the pseudohomophone
  effect.

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The Lexical Decision task
PLANE PLAIN BRAIN BRANE BOKIM
Time taken to identify words is
recorded. Non-words take longer than
words Non-word homophones take longer than
non-words that are not phonemically similar
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Proof-reading and letter search errors

• People are more likely to miss unpronounced
  letters (e.g., silent 'e's) than pronounced
  letters
• This has been found for both vowels (the e in
  insane v. eat) and consonants (the p in
  psychology v. practice).
• Evidence from lexical decision studies and
  proofreading studies suggest that people will
  access phonemic information even when it
  decreases performance,
• Indicates they may be accessing the information
  automatically.
• That suggests speech recoding is an automatic
  process.

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Evidence for visual access

• Deaf readers. People who are deaf are probably
  not using speech recoding, but they can still
  learn to read.
• Proofreading studies involving deaf children
  detect about the same number of silent and
  pronounced "e"s, while hearing children detect
  fewer silent than pronounced "e"s.
• This suggests that reading by deaf people
  involves direct visual access, rather than speech
  recoding, to translate the written symbols into
  their meaning.

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Word identification is fairly automatic
BLUE
GREEN
BLACK
GREEN
RED
RED
GREEN
BLACK
RED
The Stroop Effect (Stroop, 1935)

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Ellis Young Model of Reading
Schematic of the Dual Route Model of Reading
Acquisition  
PRINT
Letter Recognition
Graphemic Parsing
Visual Input Lexicon
Grapheme to Phoneme
Semantic System
Phoneme Level
Speech Output Lexicon
Phonemic Blending
Spoken Response
Route 1 Route
2 Route 3
Source Ellis Young (1995)
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Evidence for phonological and visual access

• Acquired dyslexia or alexia. Some people who have
  suffered left hemisphere brain damage have
  specific reading deficits.
• These deficits result in accurate silent
  reading, but impaired reading aloud.
• However, the articulatory system doesn't seem to
  be the source of the difficulty, because they can
  repeat words if someone says the word first.
• There are different types of dyslexia/alexia
  e.g. deep, phonological and surface.

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Strokes

• Most common type of brain injury
• Disruption of blood supply to the brain
• burst artery (haemorrhage)
• blocked artery (blood clot)
• Paul Broca (1860s)
• right handed people - language problems occur
  after damage to the left hemisphere of the brain
• left hemisphere responsible for language
  abilities (incl. reading and writing)
• Aphasias
• Disorders affecting the comprehension or
  production of language
• Different types depending on which aspects of
  speech processing have been impaired (Ellis
  Young, 1988)
• When reading problems are the predominant
  symptom Acquired Dyslexia

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Acquired Dyslexia

• Carl Wernicke (late 18th Century)
• Neurologist
• Mid-1970s
• Cognitive Neuropsychology
• What do these patients tell us about
• The way in which we access the meaning of a word
  in reading?
• The way we read a word aloud
• Can we explain the data from these patients in
  terms of models of normal cognitive function?
• Ellis Young (1988) Dual-Route Models
• Should we abandon them?
• Single word reading
• Models of word recognition
• box and arrow flow diagrams
• Connectionist models

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Shallice Warrington (1980)

• Patients differ in terms of severity of
  impairment but more importantly, the nature of
  the reading disability varies
• Peripheral Central Acquired Dyslexias
• Peripheral Dyslexia
• Damage to the visual analysis system
• Perception of letters in words is impaired
• Central Dyslexias
• Damage to processes beyond the visual analysis
  system
• Comprehension and/or pronunciation of written
  words

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Peripheral Dyslexias Neglect Dyslexia

• Ellis, Flude Young (1987)
• Patient VB
• Stroke affected right hemisphere
• Speech unimpaired
• Problems reading
• Sometimes (12) the patient omitted the first
  letter
• CAGE gt age LEVER gt ever
• More commonly the first letter was substituted
• ELATE gt plate PEACH gt beach
• LIQUID gt squid a kind of sea creature
• Visual problem
• Identification of words spelled aloud to her
  excellent
• Rotation of passage of text 90 degrees
  improvement
• Errors involved replacements rather than
  deletions
• FABLE as table not able BEAT as heat
  rather than eat

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Peripheral DyslexiasNeglect Dyslexia

• Riddoch, Humphreys, Cleton Fery (1991)
• Problem arises from failure to attend to left
  side of words
• JB
• GROSS as cross BOUGH as slough
• to left of words performance improved
• Supports attentional theory
• Different types of Neglect Dyslexia
• Reviewed by Ellis, Young Flude (1993)
• Attentional Dyslexia (Shallice Warrington,
  1977)
• Letter-by-Letter Reading (Patterson Kay, 1982)

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Central DyslexiasNon-Semantic Reading

• WLP (62yr old female progressive dementia incl.
  memory loss)
• Schwartz, Marin Saffran (1979)
• Schwartz, Saffran Martin (1980)
• 7/20 correct matches of animal names to pictures
• 18/20 correct animal names read aloud
• Not reading via meaning
• Could read nonwords irregular words
• Comprehension of written words poor
• Impaired Semantic System

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Central DyslexiasSurface Dyslexia

• Marshall Newcombe (1973)
• Reliance on sublexical route
• i.e. letter-sound conversion
• visual analysis system to the phoneme level
• Misread irregular words as regular words
• ISLAND as izland SUGAR as sudgar BROAD as
  brode
• Better reading of regular words
• Regularisation errors to irregular words
• Patterson, Marshall Coltheart (1985)
• Dual-route reading model
• Damage to the visual input lexicon
• Damage to the speech output lexicon
• Ellis Young (1988)

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Central DyslexiasPhonological Dyslexia

• Dont generally have the same speech (aphasic)
  problems as Deep Dyslexics
• Poor reading of nonwords relative to real words
• The problems with nonwords is not usually as
  severe as it is in Deep Dyslexia
• JD (Farah et al, 1996) 25-30 nonwords 75-80
  words
• WT (Coslett, 1991) 25 of nonwords 90 of words
• AM Patterson, 1982) 8 of nonwords 85 or words
• WB (Funnell, 1983) 0 of nonwords 90 of words
• No semantic errors in reading
• Some visual errors in reading (less than in Deep
  Dyslexia)

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Central DyslexiasPhonological Dyslexia

• Several patients (though not all) have problems
  reading function words
• AM 90 content words 70 function words
• JD 75 content words 90 function words
• WB 90 content words 90 function words
• Several patients (though not all) have problems
  reading low imageable content words
• JD 88 HI image words 55 LO image words
• AM 90 HI image words 90 LO image words
• WB 90 HI image words 90 LO image words
• Comprehension of written words is poor in some
  patients and good in others
• WB poor at picture-word matching and deciding
  whether toast cake or bread
• AM virtually 100 on tasks of this kind
• WT was poor at comprehending abstract words

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Central DyslexiasPhonological Dyslexia

• Explanations
• Impairment to the non-lexical reading route
• All patients, though variable in terms of
  severity
• Impairment to lexical routes
• Lexical-semantic route? (WB, WT poor
  comprehension of written words but not AM)
• Lexical non-semantic route? (AM function word
  deficit JD low imageable word deficit but not
  in WB or WT)
• At least one of the two lexical routes is
  preserved.
• It is therefore clear that the deficit in reading
  unfamiliar words can persist even when patients
  whose reading comprehension of familiar words
  is remarkably well preserved (AM).
• In surface dyslexia, however, one can observe the
  reverse of this.

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Deep Dyslexia

• Marshall Newcombe (1966, 1973)
• Patients are unable to read unfamiliar words or
  nonwords correctly e.g. BLASP
• Demonstrate no ability to match words and
  psuedohomophomes (FOX PHOKS)
• Their reading of familiar words is much better.
  However, they are particularly poor at reading
  function words (e.g. because) and words of low
  imageability
• High Imageability Low Imageability
• mouth cause
• hospital purpose
• horse moment

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Deep Dyslexia

• Visual Paralexias
• Participants make a preponderance of visual
  errors often referred to as visual paralexias
• An error in response to a written word
  paralexia
• An error in response to spoken word
  paraphasia
• When a participant makes a visual error, they
  respond with a word that is visually similar to
  the word they are trying to read
• i) DUGgtbug ii) PAMPERgtpaper iii) WASgtwash
  iv) UNIVERSALgtuniversity
• The error can occur at
• The start of the word (i)
• The middle (ii)
• The end (iii, iv)
• Response is of higher imageability than target
• Semantic Paralexias
• BOAT gt SHIP ILL gt SICK
• Sometimes both visual semantic
• SYMPATHY gt ORCHESTRA

The error can involve Substitution (i,
iv) Omission (ii) Addition (iii)
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Video

• Reading for Meaning
• A Case Study of Deep Dyslexia
• Funnell, E., Humphreys (Eds)

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Deep Dyslexia

• Level of impairment in Deep Dyslexia
• Right Hemisphere Reading (e.g. Coltheart, 1980,
  1987 see also Morton Patterson, 1987 Michel et
  al, 1996 Weekes et al, 1997 Price et al, 1998
  Coltheart, 2000)
• Severe Left Hemisphere Damage
• Relying on rudimentary right hemisphere reading
  system (can only deal with high imageability
  words)
• Why should such a system exist?
• Why the partial recovery in Klein et als
  patient?
• Why do some patients make semantic errors in
  picture naming as well?

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Research in Practice

• http//www.dyslexia-inst.org.uk/assess.htm