Know how brain separates ability to talk, write

Ever wondered why someone who cannot write a grammatically correct sentence may be able say it aloud flawlessly? This is because writing and talking are independent systems in the brain, says a new research.

"Actually seeing people say one thing and -- at the same time -- write another is startling and surprising. We do not expect that we would produce different words in speech and writing," said lead researcher Brenda Rapp, professor at Johns Hopkins University in the US.

"It is as though there were two quasi-independent language systems in the brain," Rapp said.

The researcher found it is possible to damage the speaking part of the brain but leave the writing part unaffected -- and vice versa -- even when dealing with morphemes, the tiniest meaningful components of the language system including suffixes like "er," "ing" and "ed."

The team studied five stroke victims with aphasia, or difficulty in communicating.

Four of them had difficulties writing sentences with the proper suffixes, but had few problems speaking the same sentences. The last individual had the opposite problem -- trouble with speaking but unaffected writing.

The researchers showed the individuals pictures and asked them to describe the action. One person 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 findings showed that although the human ability to write evolved from our ability to speak,writing and speaking are supported by different parts of the brain -- and not just in terms of motor control in the hand and mouth, but in the high-level aspects of word construction.

The study appeared in the journal Psychological Science.