Chapter 16
Interactions between Speech Sound
Disorder and Dyslexia
Beate Peter
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Introduction
• Written language is acquired several years after spoken
language
• This is true for all types of representing speech sound with
symbols (logographic symbols, alphabetic script,
syllabaries)
• In English, the relationship between alphabetic symbols
and speech sounds is extraordinarily complex
• The purposes of this chapter:
– Describe the core and associated characteristics of dyslexia
– Show how dyslexia and speech sound disorder (SSD) are related
– Consider possible subtypes and shared substrates in dyslexia
and SSD
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The Written Code of English
• “pleaf,” “meng,” “shextine”: these are all
pseudowords you can decode if you know the
regular orthography of English
– Unambiguous phoneme/grapheme relationship for
“m, n, f”
– Two symbols, one sound for “sh” (digraph)
– One symbol, two sounds: “x”
– Rules:
• The magic e makes the vowel say its name (“makes,”
“name”)
• When two vowels go walking, the first one does the talking
(“sea,” “road,” “rain”)
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• More complex grapheme/phoneme relationships
– One phoneme can be represented by several
graphemes
• /i/ can be represented with “ea” (“sea”), “ee” (“see”), “ie”
(“believe”), “ei” (“receive”), or “e” + consonant (C) + “e”
(“cede”)
– One grapheme can stand for several phonemes
(although this occurs less frequently)
• “th” before a vowel is used to represent both /θ/ (“thistle”)
and /ð/ (“this”)
– English has a deep (“opaque”) orthography
– Examples for shallow (“transparent”) orthographies
are Spanish and Italian
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• English contains many sight words that must be memorized because they
do not follow standard rules
– “have,” “done,” “gone” all defy the magic e rule
– “bread” defies the rule about the two vowels going walking
– “caught,” “sought,” “draught,” “laugh,” and “should” are full of silent letters
and other irregularities
• Reasons for these irregularities
– English has many grandparents
•
•
•
•
Anglo-Saxon: “answer”
Vikings: “horse,” “wagon,” “sell”
French: “indict,” “jury,” “sovereign”
Latin and Greek: “-tion,” “bio-”
– English orthography does not reflect historical changes in pronunciation
patterns
• “knee,” “knife,” “honor” used to be pronounced without silent letters
• “Thus an intelligent child who is bidden to spell debt, and very properly
spells it d-e-t, is caned for not spelling it with a b because Julius Caesar
spelt the Latin word for it with a b.” (George Bernard Shaw, 1942)
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• Mastery of any alphabetic writing system requires
– Phonemic awareness so that units of sound can be associated
with units of spelling
– Knowing that letters are arranged in directional sequences
– Knowing that printed words represent sentences and concepts
– Knowing how to hold a book
• Mastery of English also requires
– Learning the complex sound/letter relationships
– Automatized recognition of sight words by shape
– Understanding that each word consists of at least one syllable
and that each syllable contains one vowel (both in sound
structure and spelling)
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Dyslexia
•
Dyslexia is specific disability that interferes with the acquisition of written
language
– at the word level,
– characterized by deficits in accurate and/or fluent word recognition, decoding, and spelling.
– These difficulties are not associated with variations in cognitive ability or quality of reading
instruction,
– and they are thought to have a neurobiological origin. (International Dyslexia Association)
•
What dyslexia is NOT:
– A 10-year-old boy who had been kept from going to school and could not read in 4th grade.
(Lack of access to instruction)
– A girl in 5th grade who could read words without problems but could not answer questions
about paragraphs she read. (Perhaps poor inferencing skills or memory problems)
– A girl in 6th grade who also had difficulty following orally presented information. (General
comprehension deficit)
•
•
In the past, poor readers only qualified for extra help if their reading scores were
lower than their verbal or nonverbal IQ scores (discrepancy criterion).
Alternative: Response to Intervention (2004 Reauthorization of the Individuals
with Disabilities Education Act (IDEA) )
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Associated Behaviorally Observed
Deficits
• NOTE: Not all associated traits might be present in the same
individual!
• Auditory perception of nonspeech sounds that were presented
rapidly
• Phonological processing skills (dissect words into parts, deleting
sounds, moving sounds)
• Phonological short-term memory: nonword repetition tasks
• Retrieving word forms from long-term memory, e.g., in rapid
naming tasks
• Slowed processing speed
– Children with dyslexia had slower response times than typical controls
during motor, visual, lexical, grammatical, and phonological measures
as well as in rapid naming (Catts, Gillispie, Leonard, Kail, & Miller,
2002)
– Everyone seems to have a built-in speed limit across various timed
tasks and children with poor reading scores have slower speed limits
than children with average reading scores (Peter & Raskind, 2011)
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Associated Anatomical and Physiologic
Deficits
• Brain structures
– Grey matter
• Abnormal neuron migration to cortical layers
• Planum temporale in left and right hemisphere equal in size (typically, it is
smaller in the right hemisphere)
– White matter
• Left hemisphere in temporoparietal tracts
• Corpus callosum
• Brain functions
– Underactivation in the left fusiform gyrus (occipitotemporal system)
where visual information is processed to facilitate word recognition
– Underactivation in the left superior temporal gyrus (temporoparietal
system (where phonological information is processed)
– Underactivation or overactivation in the left inferior frontal gyrus
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Brain activation in typical readers
Inferior frontal gyrus,
including Broca’s area
(articulatory
recoding)
Temporoparietal
system, including
planum temporale,
angular gyrus
(phonological
processing)
Occipitotemporal
system, including
fusiform gyrus (word
recognition)
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Brain activation in readers with dyslexia
Inferior frontal gyrus,
includes Broca’s area:
over- or
underactivated
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Genetic Findings
• Strong evidence of a genetic etiology
• Causal gene(s) not yet identified
• Nine major candidate regions on
chromosomes 1, 2, 3, 6, 15, 18, and X
• New regions continue to be identified
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Demographics of Speech Sound
Disorder and Dyslexia
• Miles: first-grader with massive difficulties in speech and
also in learning to read: coincidence or due to the same
deficit?
• SSD
– 15.6% of three-year-old children (Campbell et al., 2003).
Criterion: 75% intelligible speech
– 3.8% in 6-year-old children (Shriberg et al., 1999). Criterion: 1.14 SD in a 20-item articulation test
– 1.1% in Australian 1st – 6th graders, using teacher report and SLP
report (McKinnon et al., 2007)
• Dyslexia
– 5% to 9% of school-age children (reviewed in Francks et al.,
2002; Pennington & Bishop, 2009; Peterson et al., 2007)
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Simple view of reading (Gough & Tunmer, 1986
Good word
recognition
Poor word
recognition
Good listening
comprehension
(Beyond single
words:
Comprehend text
better when it is
read to them)
Dyslexia
Poor listening
comprehension
Specific
comprehension
deficit (hyperlexia)
Mixed
comprehension
deficit
Subtypes by reading skill
Intact word recognition but impaired decoding: “phonological dyslexia
Intact decoding but impaired word recognition: “surface dyslexia”
Both skills impaired: “deep dyslexia”
Sight words can be trained; persistent difficulty with decoding is seen more
frequently in children with dyslexia
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SSD and Dyslexia Comorbidity
• SSD alone (not including childhood apraxia of speech, CAS): no
elevated risk of developing dyslexia in school years (Lewis et al.,
2004)
• CAS alone: substantial difficulties with reading and spelling (Lewis
et al., 2004)
• SSD + phonological deficits: substantial difficulties with reading and
spelling, regardless of whether language impairments were seen
(Bird et al., 1995)
• SSD that persists into the school years: lower scores in reading,
reading comprehension, spelling, and math, compared to children
whose SSD had resolved prior to entering school (Nathan et al.,
2004)
• SSD + language impairment: substantial difficulties with reading and
spelling (Sices et al., 2007)
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Substrates Common to Speech
Production and Literacy Skills
• Phonological awareness and processing
• Sequential processing (possibly)
• It is possible that there is a shared genetic
etiology
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Connections
• It is possible that certain SSD subtypes are
more susceptible to reading difficulties.
Chapter 15 focuses on SSD subtypes.
• Chapter 22 describes professional settings
where speech-language pathologists join
service teams working with children who
struggle with reading and spelling
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Concluding Remarks
• SLPs frequently work with children with SSD
and/or language impairment who also struggle
with written language
• Good coordination among the team of service
providers can enhance treatment efficacy, for
instance when the underlying deficit is in
phonological awareness and processing
• Additional research is needed to better
understand the biological aspects of SSD and
dyslexia comorbidity
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