Whenever I hang out with Brits or Aussies I have to stop myself from speaking with their accents. No, this embarrassing habit does not mean I have foreign accent syndrome. Rather people with the syndrome start speaking with a foreign accent following a severe brain injury that affects the speech area of the brain. This phenomenon made the news recently after a British woman's migraine caused her to start speaking with what sounds like a Chinese accent. You can listen to her in this video.
CNN also interviewed an American woman who unwillingly adopted a British accent. Although she was born in Indiana and never even visited England, she's now using British phrases and mannerisms to go along with her accent. Science says that foreign vocabulary and syntax are not a result of the injury. In fact, people with foreign accent syndrome do not really acquire a foreign accent, but rather their speech has been impaired in a way that it sounds like it. So if a stroke causes someone to lose the ability to pronounce "Rs," you might think she sounds Bostonian when she says she's going to "pahk the cah"!