Prof. Yair Neuman of
Ben-Gurion University of the Negev sent me this paper:
Computerized assessment of syntactic complexity in Alzheimer’s disease:
a case study of Iris Murdoch’s writing. Serguei Pakhomov, Dustin Chacon, Mark Wicklund, Jeanette Gundel
Behavior
Research Methods March 2011, Volume 43, Issue 1, pp 136-144
Understanding
the paper in depth requires broader linguistic knowledge than I have, but it's main
ideas are quite interesting.
Apparently,
it's possible to track signs of cognitive impairment/ decline (as occurs in Alzheimer's disease, for example) by written or
oral language analysis that measures aspects like syntactic complexity of
the sentences, idea density, use of referring
expressions and discourse coherence.
The early
linguistic signs of Alzheimer's disease are manifested in semantic declines. Semantically "empty" speech
characterized by overuse of pronouns has been noted as one of the distinctive
features of the disorder, as well as semantic deficits affecting one's ability
to determine semantic relatedness between concepts. Cognitive declines in Alzheimer's disease are
also associated with poorer performance in tasks related to working memory,
especially in the more advanced stages of the disease. Syntactic complexity in healthy people is associated
with working memory demands and is predictive of the processing time in
sentence comprehension.
Iris Murdoch is an Irish philosopher and
writer, and is certainly one of my favorite writers. Murdoch lived in 1919-1999, and published 25
books and philosophy works. Her first
book was published in 1954 and her last – four years before her death – in 1995. I especially like her book "The nice and
the Good" and warmly recommend it.
In
1997 Iris Murdoch was diagnosed with Alzheimer's disease. This diagnosis was confirmed after her death
by pathology results.
Iris
Murdoch's books are especially suitable for linguistic analysis because she
resisted any editing of her writing prior to publication, so it's safe to
assume that her books are representative of her actual language production.
There are
several manual and computerized methods for semantic and syntactic text
analysis. For example, it's possible to
count the average number of words per sentence, the average number of clauses
per sentence, the proportion of times ten most common words in each text are
repeated within the space of five words, etc.
This study
used computerized methods to analyze the syntactic complexity in four Iris
Murdoch books: her first book
("Under the Net"), published in 1954, "The Sea, The Sea", published
in 1978, "The Green Knight" , published in 1994 and "Jackson's
Dilemma", published in 1995. The researchers
analyzed 20 randomly selected passages (that did not contain dialogues) from
each book.
A clear
pattern of decline in sentence length, number of clauses per sentence and other
measures of syntactic complexity was found across the four books.
Syntactic
complexity declines are present in healthy elderly people (particularly older
than 74). Iris Murdoch was 75 years old
when "Jackson's Dilemma" was published and 74 years old when
"The Green Knight" was published.
Thus it's difficult to tease out the effect sizes
of normal aging and Alzheimer's disease (since there are no age and education based
norms for written output).
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