Ever met someone who seemed eloquent enough but came across as semi-literate on Facebook? Or have you ever said a grammatically correct sentence out loud but written down something entirely different?
The reason for that, according to new research from Johns Hopkins University, is because the brain separates our ability to speak and write - so much so that it is possible to damage one part but leave the other unaffected.
"Actually seeing people say one thing and - at the same time - write another is startling and surprising. We don't expect that we would produce different words in speech and writing," said lead author, cognitive scientist Professor Brenda Rapp. "It's as though there were two quasi-independent language systems in the brain."
To find this out, the team studied five people who had aphasia after a stroke. Four of them had difficulty writing grammatically correct sentences, but they did not have an issue speaking. One individual had the opposite problem.