http://dailynews.yahoo.com/headlines/hl/story.html?s=v/nm/19980902/hl/br9_1.html
NEW YORK, Sep 02 (Reuters) -- The timing of events described in a
sentence affects how the brain processes
and understands that sentence, researchers say.
Comparing levels of brain activity involved in reading sentences
beginning with the words ``before'' or ``after,'' a
team of researchers have concluded that the ``'before' sentences require
additional computations.''
Their findings appear in the September issue of the journal Nature.
Dr. Thomas Munte and others at the University of California, San Diego
in La Jolla, California, explain that ``our
experiences in the real world suggest to us that time unfolds
sequentially, with current events sometimes causing
future events.''
Although this concept of the linear progression of time has infiltrated
human language, the researchers point out that
many linguistic constructions do not follow this basic rule.
They focused on two common constructions -- sentences beginning with
either ``before'' or ``after.'' Sentences
beginning with ``after'' follow real-world cause-and-effect chronology
-- ``After the rain, the grass grew.'' However,
sentences which begin with ``before'' reverse this order -- ''Before the
grass grew, it rained.''
Does the brain take longer to process language describing events
presented in reverse order? The authors had
healthy subjects read 120 sentences, half of which began with ``after''
and half with ``before.'' All of the subjects
were hooked up to electrodes which recorded brain activity at specific
sites.
``At sites on the left frontal scalp, the responses to 'before' and
'after' sentences diverge(d) within 300 milliseconds,''
the authors report, with the nonsequential (before) sentences taking
longer to process than the sequential (after)
sentences.
They speculate that 'before' sentences ``are more demanding of (the
brain's) working memory.'' The brain has to
re-order the events occurring in the sentence before the meaning (rain
helps grass grow) can be fully processed and
understood.
Previous research supports this theory. The authors note that damage to
working memory has been implicated as a
possible cause of ``the comprehension deficits that adults with
Parkinson's disease experience with 'before'
compared with 'after' sentences.''
Munte and his colleagues believe that their findings ``show the power of
a single word not only to express a concept
but also to affect sentence processing in real time.''
SOURCE: Nature 1998;395:71-73.
Copyright © 1998 Reuters Limited.
--
Judith Richards, London, Ontario, Canada
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