From 1941 to 2009 there have been over 60 documented cases of people who abruptly begin speaking in what their families and friends perceive as foreign accents. The condition known as Foreign Accent Syndrome was long thought to be psychiatric or even imagined, until Gurd et al. from Oxford University found a physiological basis. Namely, in a number of cases of patients diagnosed with Foreign Accent Syndrome, brain scans revealed substantive damage to areas postulated to coordinate linguistic ability.
Individuals suffering from Foreign Accent Syndrome (FAS) report that speaking is labored and forced, akin to people suffering speech impediments. Despite sensationalist and unlikely claims including a case of a Croatian who spontaneously spoke fluent German (more on this coming soon), FAS patients do not actually adopt a foreign accent. Instead, researchers hypothesize that damage to the brain results in difficulty pronouncing certain tones/pitches/phenomes, resulting in modified speaking patterns.
Notably, brain damage might impair the ability to pronounce terminal “r” sounds, endowing non-Bostonians with the characteristic, terminal “r”-less Boston accent. Though other key features of the accent may be missing, people who interact with the FAS patient likely experience pareidolia (which, though unrelated, is attributed to the “Face on Mars” photo).
Clinicians postulate the disorder likely results from physical trauma to the brain or from stressful experiences including stroke.