Brett Smith for redOrbit.com – @ParkstBrett
Written and oral language may seem like they come from the same part of the brain, but a new study in the journal Psychological Science has found that separate systems in the brain are responsible for our ability to speak or write.
In the study, researchers discovered a person can sustain damage to the speaking part of their brain, but have the writing part unaffected, vice versa. The researchers said this even holds true for morphemes, the smallest meaningful aspects of the English language that includes suffixes like “-er,” “-ing” and “-ed.”
“Actually seeing people say one thing and — at the same time — write another is startling and surprising,” said study author Brenda Rapp, a professor of cognitive science at Johns Hopkins University. “We don’t expect that we would produce different words in speech and writing.”
“It’s as though there were two quasi-independent language systems in the brain,” she added.
Studying aphasia
The study team set out to understand how the brain is organized with respect to reading and spelling. More specifically, the team said they wanted to know if written language was based on spoken language in people who are literate.
To reach their conclusion, researchers worked with five stroke victims with aphasia, a condition marked by communication problems. Four participants had trouble writing sentences with the correct suffixes, but had few difficulties speaking the same sentences. The last volunteer had the reverse problem.
The study team asked individuals to describe actions being shown in a series of pictures. One participant would say, “The boy is walking,” but write, “the boy is walked.” Or another would say, “Dave is eating an apple” and then write, “Dave is eats an apple.”
The team said if written language is based on spoken language, then they should see similar errors in speech and writing. However, researchers saw that people don’t always write what they say.
“We found that the brain is not just a ‘dumb’ machine that knows about letters and their order, but that it is ‘smart’ and sophisticated and knows about word parts and how they fit together,” said Rapp. “When you damage the brain, you might damage certain morphemes but not others in writing but not speaking, or vice versa.”
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