Thursday, May 26, 2011

Studies supporting phonological deficiences in Dyslexia

Hamalainen, J. A., Leppanen, P. H. T., Eklund, K., Thomson, J., Richardson, U., Guttorm, T. K., Witton, C., Poikkeus, A. M., Goswami, U., Lyytinen, H. (2009). Common variance in amplitude envelope perception tasks and their impact on phoneme duration perception and reading and spelling in Finnish children with reading disabilities. Applied Psycholinguistics, 30(3), 511-530. DOI 10.1017/S0142716409090250
"Our goal was to investigate auditory and speech perception abilities of children with and without reading disability (RD) and associations between auditory, speech perception, reading, and spelling skills. Participants were 9-year-old, Finnish-speaking children with RD (N = 30) and typically reading children (N = 30). Results showed significant group differences between the groups in phoneme duration discrimination but not in perception of amplitude modulation and rise time. Correlations among rise time discrimination, phoneme duration, and spelling accuracy were found for children with RD. Those children with poor rise time discrimination were also poor in phoneme duration discrimination and in spelling. Results suggest that auditory processing abilities could, at least in some children, affect speech perception skills, which in turn would lead to phonological processing deficits and dyslexia."

"one- and two-ramp rise time discrimination and AM [amplitude modulation] detection thresholds were associated in children with RD, and the interaction between group status and rise time sensitivity explained significant additional variance in spelling performance." 

In plain English, amplitude modulation is important for speech perception. Children must learn to discriminate speech sounds that they hear to identify meaningful speech units. Children with dyslexia show evidence of insensitivity to speech sounds. 

"Further, performance in the rise time tasks was associated with phoneme duration discrimination, which in turn, was associated with spelling. This could indicate a possible developmental route whereby basic auditory skills could affect spelling performance in children with RD, as indicated by the path analysis. However, the current study measured only a limited number of speech perception and auditory processing skills. Further studies are needed to fully understand the relationship between auditory processing and reading disabilities, taking into account the development of auditory, speech perception, phonological, and reading and spelling skills, using both behavioral and brain activation measures."

Note on this study: Perhaps children with well-developed orthographic knowledge do better on phoneme discrimination tasks because they have the aid of spelling knowledge. Back to the question - is it phoneme sensitivity that matters or phoneme identity in learning to read?

Fraser, J., Goswami, U., Conti-Ramsden, G. (2010). Dyslexia and specific language impairment: The role of phonology and auditory processing.  Scientific Studies of Reading, 14(1), 8–29 DOI: 10.1080/10888430903242068

"We explore potential similarities between developmental dyslexia (specific reading disability [SRD]) and specific language impairment (SLI) in terms of phonological skills, underlying auditory processing abilities, and nonphonological language skills. Children aged 9 to 11 years with reading and/or language difficulties were recruited and compared to chronological-age controls on phonological skills (rhyme awareness, rhyme fluency, phoneme awareness, phonological short-term memory), nonphonological language skills (vocabulary, grammatical morphology, sentence processing) and auditory processing of rise time and intensity. The SRD children performed poorly on all phonological awareness tasks and had significantly poorer rise time perception. The SLI children showed consistent impairments in phonological and nonphonological but not auditory skills. The SLI/SRD group showed consistent impairments across phonological and nonphonological skills and auditory processing. It is concluded that there is substantial overlap between these disorders at the level of phonological skills and auditory processing, and shared variance with nonphonological language skills."

Strengths of SRD students: 
average to high intelligence
average - good vocabulary scores (Richardson, Thomson, Scott, & Goswami, 2004)
sufficient semantic-processing skills (Nation & Snowling, 1998)
accurate at recall (Kahmi&Catts, 1986)

-some found to have poor grammatical morphology skills (perhaps linked to insensitivity to inflected endings). (Joanisse & Seidenberg, 1999) hmm. . . 
-poor orthographic knowledge
-Rise times in speech envelope correlated with  onsets of syllables, particularly stressed syllables (p. 11).


  • Standardized tests Block Design and Picture Completion subtests of the Wechsler Intelligence Scale for Children (3rd ed. [WISC–III]; Wechsler, 1992)
  • Phoneme awareness. 
    • Phoneme  deletion task (McDougall, Hulme, Ellis, & Monk, 1994; see Pasquini et al., 2007).
    • Rhyme oddity. A rhyme oddity task (Thomson & Goswami, 2008)
    • Rhyme fluency. Rhyme fluency (Nation & Snowling, 1998b)
    • Phonological short-term memory. PSTM (Pickering and Gathercole, 2001)
  • Vocabulary. Receptive vocabulary was assessed using the British Picture Vocabulary Scale (BPVS; 2nd ed.; Dunn, Dunn, Whetton, & Burley, 1997). Expressive Vocabulary subtest of the WISC–III (Weschler, 1992).
  • Semantic skills. CELF–III  word associations task (semantic fluency).
  • Grammatical morphology.
    • generate past tense inflection
    • notice and correct grammatical errors in a sentence.
  • The past tense elicitation task (Marchman et al., 1999).
  • The sentence correction task was an adapted form (Kamhi and Catts (1986).
  • Sentence processing. Recalling Sentences subtest of the CELF–III (Semel et al., 2000)
  • Auditory Processing Skills Three (Richardson et al., 2004; Corriveau et al., 2007)
    • Intensity Task (AXB)
    • Rise Time From a Carrier Task (2 Ramp Rise)
    • Amplitude Envelope Onset Task (1 Ramp Rise)
  • Sentence correction task  (Kamhi and Catts, 1986).
"-Phonological measures played the greater predictive role in reading development . . .
-Basic auditory measures of rise time processing (2 Ramp Rise and 1 Ramp Rise) showed elevated thresholds in all three groups with developmental difficulties . . .
-The children with reading difficulties only were not impaired in the grammatical morphology,
sentence correction, and sentence recall tasks, or in receptive vocabulary" (p. 26)
-"Phonological skills were strong concurrent predictors of language skills, and nonphonological skills were significant predictors of reading ability" (p. 27).

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