SPOKEN WORD PROCESSING

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SPOKEN WORD PROCESSING

• AIMS OBJECTIVES
• The aim of this lecture is to review models of
  spoken word recognition/production.
• At the end of the lecture you will have learned
  about
• The definition of a morpheme
• Mortons model of word recognition
• Lexical and nonlexical processing
• The meaning of the term aphasia

• CORE READING
• Parkin, A. (2000). Essential Cognitive
  Psychology. Psychology Press, Chap 10.
• SUPPLEMENTARY READING
• Hickok, G., Poeppel (2000). Towards a
  functional neuroanatomy of speech perception.
  Trends in Cognitive Sciences, 4(4), 131-138.
• Ellis, A. and Young, A. (1996). Human cognitive
  neuropsychology. Psychology Press, Chapter 78.

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Brocas area expressive
Wernickes area receptive
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Wernickes speech sample

• Doctor Why did you come to hospital?
• Patient Never, now mista I wanna tell you this
  happened when happened when he rent. His - kell
  come down here and is - he got ren something. And
  he roden all these arranjen from the pedis on
  from is pescid.

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Brocas speech sample

• Doctor Why did you come to hospital?
• Patient AhMondayah Dad and Pauland
  Dadhospital. Twoahdoctorsand thirty
  minutesand yesahhospital. Wednesdaynine
  oclockdoctors. Two doctorsand ahteeth.
  Yeahfine.

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The lexicon

• Mental lexicon
• our internalised knowledge of words
• this is sometimes thought of as a dictionary.
• Paivio referred to the representation called a
  logogen word form

• Lexical access codes
• processes of word identification
• can be visual, phonological or semantic.

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Morphemes

• Aphasic patients
• Do not understand spoken words but are not deaf
  and can read words OK.
• Pure word deafness cases.
• Wernickes aphasia refers to problems
  understanding morphemes lexical.
• Brocas aphasia refers to problems producing
  words.

• The smallest unit of language that has a meaning
  is called a morpheme a word.
• single words - dog, fly
• plurals -s, past tense -ed
• Some words have more than a single morpheme
• e.g., Handgun

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Spoken word recognition

• Morton (1970) proposed a stage model of auditory
  word recognition distinguishing between 3 phases

• Auditory analysis system
• identifies phonemes in the speech wave.
• Auditory input lexicon
• identifies phonological properties of known words
  i.e. logogens.
• Semantic system
• identifies the meanings of known words.

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Non-lexical pathway no logogens
Lexical pathway logogens
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Mortons logogen model

• Each word is represented by a logogen.
• Logogen is literally from
• logus word
• genus birth

• A device that collects information that a word is
  represented in long term memory.
• No semantic or meaning information in the
  logogen.

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Threshold mechanism

• A threshold criterion is used by the spoken word
  recognition system.
• A logogen is activated by data driven input and
  contextual information.

Spoken input
Lexicon is arranged by frequency
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Pure word deafness

• Hempel and Stengel (1940).
• 34 year old patient who fell from a bus.
• First thought to be deaf
• Make use of lip reading.
• Perception of nonverbal environmental sounds
  intact e.g. a cow mooing.

• I can hear you dead plain but I can't understand
  what you say. The noises are not quite natural.
  I can hear but not understand.
• Vowels are detected better than consonants.
• Slowing the rate of speech can improve
  performance.

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Blumstein et al (1977)

• Word meaning deafness patients were asked to
  discriminate between "da and pa".
• Sounds distorted so that the acoustic properties
  fell on to a continuum.

• Controls show a clear point when their
  discriminations of phonemes change.
• Pure word deafness patients had "fuzzier" phoneme
  boundaries compared with normal age matched
  controls.

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Fuzzier boundary
Hear DA?
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perceptual analysis
logogen analysis
Wernickes aphasia
Brocas aphasia
Deep dysphasia Repeat wordsgtnonwords
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Wernickes aphasia
temporal

• Comprehension of morphemes becomes impaired
  (dog/dogs).
• Speech is fluent, but full of neologisms
• these are nonlexical forms e.g. fep.
• Grammatical structure is usually preserved.

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hat
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Brocas aphasia

• Comprehension of morphemes is normal.
• Speech is non-fluent, slow and laboured.
• Grammatical structure is absent (agrammatism).

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Summary

• Spoken word recognition and production involves
  lexical and nonlexical processes.
• Data from aphasia patients particularly those
  with Brocas and Wernickes aphasia supports the
  model.