Scripts, Layout and Segmental Awareness

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Scripts, Layout and Segmental Awareness

• Richard Sproat
• SALA 25
• September 15-18, 2005
• University of Illinois at Urbana-Champaign

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Overview

• Computational model of script layout
• Application to Brahmi-derived scripts
• Implications for phonemic awareness
• Are readers of Indian scripts aware of phonemes?
• A computational model of scriptal influence on
  phonemic awareness
• Further issues phonology or writing?

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Computational Theory of Writing Systems

• Relation between writing and language is a
  regular relation (in the sense of formal language
  theory)
• Writing tends to represent a consistent level of
  linguistic representation
• Glyphs are combined via a small set of
  two-dimensional catenators

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Two-Dimensional Catenators
95 of Chinese Characters ever invented consist
of a semantic and a phonetic component
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?
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Brahmi-Derived Indic Scripts
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Properties of Indic Scripts

• Glyphs are arranged into orthographic syllables,
  called aksara -CV- CV- CV -
• Within each aksara
• consonant sequences are first composed together
  using various script/glyph-dependent catenators
• then vowels are arranged around the consonant
  glyphs using various catenators
• Word-initial vowels are written in a full form
• A consonant (sequence) written with no vowel
  symbol is understood to have an inherent vowel

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Devanagari Vowels
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Kannada Diacritic Vowels
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(No Transcript)
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(No Transcript)
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g(x) graphical expression of phone x
gr(x) reduced form
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Script Index Feature Vectors
expressed,catenator,reduced,fused,complex,transpa
rent
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Summary of Formal Treatment

• The theory explicitly treats Indic writing
  systems as segmental
• At an abstract level, symbols are just catenated
  together the particular mode of catenation is
  only an issue of rendering.
• Cf. text transmission standards such as Unicode.
• But do Indic writing systems behave segmentally?

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Alphabets and Segmental Awareness

• A Claim Readers of non-alphabetic writing
  systems have no conscious awareness of segments
• investigations of language use suggest that many
  speakers do not divide words into phonological
  segments unless they have received explicit
  instruction in such segmentation comparable to
  that involved in teaching an alphabetic writing
  system (Faber, 1992)
• According to Faber, only Western alphabets, which
  represent both vowels and consonants inline,
  count as alphabetic
• Indic scripts are not alphabetic, so readers
  should not have segmental awareness

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Fabers Criteria

• Faber classifies scripts according to two main
  criteria
• Are all segments represented?
• Are all segments represented linearly with vowels
  and consonants on a par (versus with some being
  diacritics)

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Fabers Classification of Scripts
Korean
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Ethiopic (Geez)
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Is Segmental Awareness a Biproduct of Literacy in
an Alphabetic Script?

• Recently literate Portuguese speakers outperform
  illiterates on phonemic segmentation
• Japanese school children are less able to perform
  segmental manipulation tasks than their American
  counterparts
• Chinese readers who have been exposed to the
  pinyin transliteration system outperform Chinese
  readers who have not had this exposure.
• Conclusion literacy per se is not sufficient for
  phonemic awareness to develop. One needs an
  alphabet.

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Segmental Awareness in Korean(Sohn, 1987)
Vowel switching
o
a
This is not expected on Fabers account
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Segmental Awareness in Indian Languages

• Padakannaya (2000) tested awareness of syllables
  and phonemes
• Syllable manipulation rhyme recognition,
  syl.deletion,syl. reversal even illiterate
  speakers can handle these.
• Phoneme manipulation ph. oddity, ph. deletion,
  ph. reversal these cause problems for
  readers of non-alphabetic writing systems.
• Compared sighted children, who learned the
  Kannada script with blind children who learned a
  purely alphabetic Kannada Braille.
• Blind children consistently outperformed sighted
  children on segmental manipulation tasks.

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Phoneme Reversal
Kids start learning English
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Phoneme Awareness and Graphic Prominence

• Phonemic awareness in Kannada and other Indic
  writing systems is affected by how noticeable
  the components are (Padakannaya et al, 1993)
  this varies cross-scriptally.
• Thus, Hindi speakers find it hard to treat
  anusvara and repha as separate segments.
• But this is easy for Kannada speakers

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Diacritics Cross-Scriptally

• In Devanagari, anusvara is a diacritic
• Also find it easier to delete /y/ in
  than /r/ in
• Diacritics are less salient than non-diacritics
  in other scripts. E.g. work of van Heuven (2002)
  for Dutch
• Errors in placement of diaeresis e.g. Bedouïen
  Bedouin have no effect on word recognition,
  unlike errors in letters, which have a
  significant effect.
• But diaeresis is required according to the Dutch
  spelling conventions without the diaeresis
  Bedouien should be pronounced b?duj? rather
  than (correct) beduin

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Phonemic Awareness and

• Hindi speakers find it easier to delete /d/ in
  doshii than they do /n/ in nadii
• Vaid and Gupta (2002) show that (inline) /i/ in
  Devanagari seems to be treated as a separate
  segment in reading.

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Vaid Gupta (2002) Evidence for Devanagari as
an Alphabet

• Studied naming latencies in Hindi-speaking adults
  and naming errors in Hindi-speaking children for
  words containing short /i/.
• Single C /tilak/
• Heterosyllabic C
  /masjid/
• If D. is a syllabary then misorder should
  only cause problems if the C sequence contains a
  phonological syllable boundary (syllable-delimited
  view).
• If D. is an alphabet then both /tilak/ and
  /masjid/ should cause problems
  (phoneme-delimited view)
• Both /tilak/ and /masjid/ show slower naming and
  higher error rates than forms not including short
  /i/.
• This is consistent with Devanagari being an
  alphabet.

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Vaid Guptas Results Naming
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Vaid Guptas Results Errors
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Kannada Reduced Consonants

• Padakannaya suggests an explanation for why
  deleting in should be
  harder than deleting the .
• He notes that in cases where there is an explicit
  vowel, this is generally ligatured with the
  .
• So the is more opaque than the
• This is not wholly satisfactory

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Proposed Model

• The ease/difficulty with which a segment is
  available for conscious manipulation is directly
  related to two factors
• The visual prominence of the graphemic
  representation of the segment
• The complexity of the editing operations involved
  in transforming the graphic form of the stimulus
  into the graphic form of the response
• How to compute edit distance?

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An Alternative Explanation Edit Operations
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Edit Operations rakta ? rata

• Delete
• Move up to inline position
• Change into full form glyph

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Edit Operations rakta ? raka

• Delete

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Edit Operations rakti ? rati

• Delete
• Move up to inline position
• Change into full form glyph, linking with

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Korean Vowel Switching
hobak (pumpkin)
habok
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Formal Model

• Cost of an edit operation is given by
• We could hope to quantify the ?s by regression
  against real psycholinguistic data

Movement cost
Deletion cost
Substitution cost
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Prominence and Similarity

• Need some measure of what it means to be a
  diacritic
• Also need a measure of similarity to quantify the
  cost of substituting one glyph form for another

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Similarity Metric for Glyphs

• 26 subjects took part in a web-based survey
• Task was to rate pairs of glyphs on a 5 point
  scale of similarity
• Least similar 1
• Most similar 5
• 153 pairs of glyphs were judged from 3 scripts
  Devanagari, Kannada and Malayalam

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Some Dissimilar Glyphs
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Some Similar Glyphs
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Are we really talking about phonology?

• Are peoples judgments of the number of sounds in
  a word influenced by
• Number of phonemes?
• Number of letters?
• Answer seems to be that both are relevant
  (Scholes, 1993)

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How many sounds in a word?

• Scholes gave explicit instructions
• at has 2 sounds
• cat has 3 sounds
• Used a verification test to make sure people had
  mastered the task

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Results
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So

• No question that judgments about segments are
  influenced by spellings of words
• But speakers still have some sense of the
  underlying phonological structure
• In Indian languages, we might assume that
  speakers knowledge of phonemes is influenced by
  the layout of symbols, but tests of phonemic
  awareness are at least in part targeting
  phonological knowledge.
• Explanation of phonemic awareness behavior seems
  to lie in understanding the graphical properties
  of the scripts involved.