CONTEXT PREDICTABILITY OF WORDS IN NORM AND SCHIZOPHRENIA

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CONTEXT PREDICTABILITY OF WORDS IN NORM AND
SCHIZOPHRENIA
Tatiana Petrova (tatianapetrova4386_at_gmail.com) Mar
ia Gutman (mariagutman_at_yandex.ru)

• St. Petersburg State University

ACKNOWLEDGMENT This research was supported by
grant from Russian Foundation for Basic Research
(No. 06-06-80152)
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INTRODUCTION

• Schizophrenia is a complex disorder
  that is frequently manifest in language and
  related cognitive dysfunction (Kuperberg GR,
  Caplan D. Language dysfunction in schizophrenia.
  In R.B. Schiffer, S.M. Rao, and B.S. Fogel (eds)
  Neuropsychiatry, 2nd edition, 2003 444-66.
  Philadelphia, PA.)

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INTRODUCTION

• A review of the literature on
  language disorder in schizophrenia (Maher 1972
  DeLisi 2001 Kuperberg, Caplan 2003) and
  investigations of our Laboratory provide evidence
  for widespread deficits in comprehension,
  production, attention, and cerebral
  lateralization of language.

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THOUGHT DISORDER

• Perhaps the most extreme and obvious
  manifestation of a language disorder in
  schizophrenia is the abnormal speech produced by
  some patients. This disturbance is heterogeneous
  and has traditionally been termed thought
  disorder. Some authors (Thomas 1995, Chaika
  1982) argue for the replacement of the term
  formal thought disorder with communication
  disorder.

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THOUGHT DISORDER

• Here are some fundamental questions
  that have been discussed in many papers
• Is it truly a disorder of thought or one of
  language?
• Is it characterized by problems in the content or
  the form of speech or both?
• Is it unique to schizophrenia?
• How has it been classified and studied?

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RESEARCH GOALS

• The purpose of the present study was to test
  context predictability of words in norm and
  schizophrenia, and to reveal whether the type of
  the text influences on its perception and
  comprehension.

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Two types of the text were used

• DYNAMIC TEXT
• event type predicates
• (denote the dynamic action)
• sequence of events following swiftly on one
  another

• STATIC TEXT
• process type predicates
• (denote the static action)
• descriptive sentences

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• Test samples were chosen from the works of
  Hemingway.
• This choice has a number of foundations
• the samples are of the same length (151 words in
  the dynamic text and 148 words in the static
  text)
• these samples are complete text fragments
• they are not of the big size
• they are quite demonstrative examples of dynamic
  and static texts correspondingly
• these fragments are not archetype texts known by
  Russian people
• they are autosemantic.

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METHOD

• Cloze-test technique first described by Taylor
  (1953) was applied. Texts were mutilated by
  deleting words at set intervals (every six word
  was deleted). Because of the inherent redundancy
  in language (not all elements of a message need
  to be apprehended for some comprehension to
  occur) it should be possible for the reader to
  fill in some, if not all.

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SUBJECTS

• 32 schizophrenic patients
• 15 males, 17 females
• mean age 36,5 (1,64) years
• illness average duration 16,7 (1,2) years
• All were diagnosed on the basis of
• International Classification of Diseases , 10th
  Edition
• (WHO World Health Organisation, Geneva, 1992)
• All schizophrenic subjects were in-patients at
  psychoneurologic dispensary ?7 and
• insane hospital ?3 of St.Petersburg

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SUBJECTS

• The control group consisted of 32 healthy
  subjects
• (16 males, 16 females) balanced by age, gender,
  education level, etc.
• All the patients were examined to evaluate
  attention, memory and IQ.
• All subjects were right-handed. The primary
  language of all subjects was Russian.

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DATA ANALYSIS

• Lexical items inserted by the subjects
  were analyzed and classified. The inserted word
  was in one of the five categories below when
  compared with the original
• 1. adequate
• identical to the original
• different, but synonymous with original word
• 2. containing a syntactic mistake
• grammatical mistake
• punctual mistake
• 3. containing a semantic mistake, when inserted
  word breaks
• sentence semantics
• text semantics (or coherence of the text)
• pragmatic component of the text
• 4. containing both (syntactic and semantic)
  mistakes
• 5. refusal

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RESULTS

• 1. Schizophrenic patients performed
  significantly worse than controls in
  reconstructing both dynamic and static texts
• filling the gaps, schizophrenic patients used to
  create their own context rather than to
  reconstruct the original text
• syntax and semantic-syntactic relations were
  highly impaired and the patients used context
  predictability less effective than controls
• patients were not able to establish formal
  logical and causal connections. They couldnt
  concentrate and suppress irrelevant associations.

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RESULTSInserted items in the dynamic text
schizophrenic patients controls
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RESULTSInserted items in the static text
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RESULTS

• Variation of inserted items was significantly
  higher in the texts reconstructed by
  schizophrenic patients
• Reconstructing the text schizophrenic patients
  used only the right context of this text. They
  didnt notice the left context.

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RESULTS

• 2. Context predictability of words was
  significantly higher in the dynamic text for both
  groups of subjects. Coefficient of agreement of
  inserted words suggested by the subjects was also
  higher for the dynamic text. Its much easier to
  predict the sequence of events than the elements
  in the static (descriptive) text.

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RESULTS

• 3. Women demonstrate much better
  ability to reconstruct the dynamic text. There
  were no differences between men and women in
  reconstructing the static text. Hence, we can
  conclude that the background knowledge helps to
  comprehend the text and to predict words in it.
  Though this conclusion is true only for the group
  of healthy subjects. So, disease factor is more
  significant than gender factor in case of
  schizophrenia.

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CONCLUSION

• Static texts are less predictable than dynamic
  ones.
• Our data strongly support the view that
  schizophrenic patients are not able to gain as
  much advantage from the redundancy of language
  (both semantic and syntactic) as the normal does.

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