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					What phonological deficit?
   Franck Ramus and Gayanesh Szenkovits
        Different theories regarding
          developmental dyslexia
   Different theories co-exist in an attempt to capture the
    mechanisms which cause developmental dyslexia- the
    magnosystem hypothesis, the temporal processing
    impairment and the phonological deficit theory. (Habib
    2000)
   Here we will focus on the phonological deficit theory and
    try to present it in a different light.
   In Ramus own words:‘’ The present paper is, at last,
    about a first significant attempt to get to grips with the
    phonological deficit’’
Phonological cognitive architecture
            assumed


                    Banana



     Ba                      Ba
      The 3 main dimensions to the
     phonological deficit rolled into 1
1. Poor phonological awareness          (phoneme deletion task -
    say ‘rock’ without ‘r’ – ‘ock’).
2. Poor verbal short term memory( poor digit span -
    1425367 – 1425???).
3. Slow lexical retrieval ( rapid automatic naming task -
    ….. Owl).
 The poor performance of dyslexics in verbal
  tasks is related to one or more of these
  dimensions.
 The three dimensions have something in
  common: They all implicate phonological
  representations, each in its own way.
    The phonological representations
     in developmental dyslexia are
               degraded
   The most commonly accepted hypothesis regarding the
    phonological deficit in dyslexia is that the phonological
    representations are degraded (Fuzzier, or noisier, or are not
    sufficiently categorical and preserve to many acoustic or allophonic details).
 Nevertheless, there is much more to phonology than
  these three dimensions.
 First, the locus and the nature of the phonological deficit
  must be explicitly defined. Moreover, the vast knowledge
  on phonology is seldom brought to bear on the
  phonological deficit hypothesis. Secondly, the
  phonological deficits predict deficits in heard language (
  Ramus 2001).
    In search of a locus-experiments
   In all the presented experiments, subjects are dyslexic
    and non dyslexic adults.
   In the first set of experiments, there was an attempt to
    find the deficient levels of phonological representations
    depicted in the suggested cognitive model.
 Lexical and sublexical levels were contrasted using words versus non-
  words.( ton vs. zan)
 Input and output pathways were contrasted by comparing repetition (both)
  tasks with auditory discrimination task (only input representations).
   Results show deficiency in both lexical and sublexical
    levels and both pathways. Furthermore, a substantial
    impairment in the input pathway. Short term memory
    load was an important factor.
     Representations vs. working
    memory processes-experiments
   Why do dyslexics fail to discriminate and repeat verbal
    material, when the short term memory load is
    significant?
   Could be because their phonological representations are degraded.
    Alternatively, it could the phonological representations are intact but the
    short term memory is limited.
   An experiment of phonological similarity was run to
    differentiate between the explanations.
   The more phonologically similar a sequence of words are the harder it is to
    recall the sequence. If the phonological representations of dyslexics are
    degraded ,there will be a different in the similarity effect compared to
    controls.
   Dyslexics show the same similarity effect as controls.
   Thus, short term limitations are argued for.
             Universal or hypernative
             phonology-experiments
   Language specific phonological representations are
    acquired very early in life by a child.( rice – lice)
   As the developmental dyslexia deficit is congenital, one known hypothesis is
    that dyslexics incompletely acquire the specific phonological category of
    their language. Thus, their phonology is less specific to any particular
    language.( Mody et al 1997)
   Thus, one prediction is that dyslexics will be able to
    perceive and perhaps produce foreign speech sounds.
   An experiment was performed using dyslexic French
    speakers, who were tested in discrimination and
    repetition of foreign Korean voicing categories.
   Again there was an assessment of short term memory load, by
    contrasting conditions of one foreign nonwords compared to
    conditions with two or three nonwords.
           Universal or hypernative
            phonology-continued
   The results showed that dyslexic were similar in
    performance to controls in single nonwords, but not in
    the two or three non word sequence.
   The results suggest that dyslexics are equally unable to
    represent foreign speech sounds as controls. Group
    differences appear only when short term memory load
    increases.
   Thus this is compatible to the hypothesis that
    phonological representations of dyslexics are intact and
    short term memory processes to operating on them
    seem to be impaired.
Phonological grammar-experiments
   This is the whole host of rule like processes that apply in
    speech production when phonological lexical items and
    assembled to make phrases. These phenomena are
    related also to speech perception, as an adaptation to
    native phonological structure.
   Most of these differences are language specific and
    learnt during acquisition of language. Do dyslexic
    children learn them as well as controls?
   In one experiment, assimilations by phonotactic
    constraints were investigated.
    Phonological grammar- continued
   In English, clusters like [dl] or [tl] can never occur in the begging of a word.
    The consequence is when subjects hear a non word such as [dla] or [tla],
    they most often assimilate it to the closest legal cluster( [gla] or [kla])
   In such a discrimination task it was found that dyslexics
    listeners fell victims to this perceptual illusion as much as
    controls, hearing [gla] instead of [dla].
   Thus, their speech perception is constrained by the
    same phonotactic of their native language as controls.
   In conclusion, the aspects of phonological grammar that
    was investigated seem perfectly intact.
    Unconscious speech processing-
             experiments
   A problem in psycholinguistics is that tasks require
    attention to the stimuli, and introspection, which may blur
    the effects observed, particularly when the population
    tested have problems with phonological awareness.
   Auditory masked priming have shown phonological lexical representations
    processed unconsciously (hospital- nurse).
   A new question can be how efficient are unconscious
    lexical access to phonological representations in
    dyslexics?
   A masked priming tasks in dyslexics replicated the results of controls.
   The results support the notion that phonological
    representation in dyslexics are not degraded and
    dyslexics rely on them and not on the acoustical level.
             A new hypothesis
 Findings converge to a conclusion: the phonological
  representation of dyslexics are normal.
 Although, subjects do have a phonological deficit
  measured by traditional tests: nonword repetition and
  rapid naming tasks.
 It seems that short term memory load is paramount to
  the deficiency of dyslexics in different tasks studied:
  such as digit span or phonological awareness tasks,
  which require holding segmented phonological units in
  short term memory and conscious access to those
  representations.
 An alternative explanation for the phonological task
  deficits is phonological access.
     A new hypothesis-continued
   Phonological access:
   Verbal short term memory requires access to
    phonological representations to copy them into buffers,
    then access for them retrieval, as well as to access input
    representation to copy them to output representation.
   Phonological awareness tasks involve conscious access
    to phonological representations, which may place special
    demands on the system.
   Rapid naming tasks require fast access to lexical
    representations.
   Thus, dyslexics seem to fail in tasks that are particularly
    demanding in phonological access.
                     Discussion
   Are the subjects dyslexic enough? Yes, the subjects had
    a history of reading disability. Furthermore, their
    performance in phonological tasks (digit span, rapid
    naming) did not match controls.
   Is working with adult subjects enough? It can be argued
    that children may have deficient phonological
    representations, but these are recovered in adulthood. A
    replication study with children is needed. This criticism
    steel don’t explain why representations have recovered,
    and additional load on phonological access have not.
   Other past articles have been coarse in defining the
    phonological deficit as shown here.
           Discussion- continued
   Its seems that deficient phonological access can be
    viewed as an executive function deficiency. This is a
    specific type of executive function, specific in processes
    and in modality.
   In relation to sensory theories, others have found that
    dyslexic never seem to have a problems in perceiving a
    certain kind of stimulus, be it auditory or visual: rather
    the difficulty is related to task requirements, and
    specifically to tasks that demand short term memory, or
    when the stimulus is noisy.
   Dyslexic can be viewed as people with dysfunctional
    sensory presentation access: most just to phonology and
    others also to other domains: visual or auditory.
                          But…
   Dyslexia: a deficit in visuo-spatial attention, not in
    phonological processing (vidyagaskar et al. 2010)
   Speech Perception Abilities of Adults With Dyslexia: Is
    There Any Evidence for a True Deficit?( Hazan
    et al. 2009)




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