As Emily Sohn noted on Discovery News, a 13-year old Croatian teenager awoke from a one-day coma last week. Her partial recovery was welcome news, but there was a strange twist: she could no longer speak her native tongue but instead communicated in German, a language she had recently been studying in school. (Some news reports claim that she awoke speaking fluent German, but this is unconfirmed and highly dubious.)

Though curious, this phenomenon is not unheard of, and seems to be a case of what’s called bilingual aphasia, in which one language is lost when another is gained.

This is not the only case of supposedly mysterious and unexplained phenomenon involving language. Subjects like demonic possession and reincarnation often involve claims of xenoglossia, or the sudden acquisition of a new language. A related phenomenon is glossolalia, also known as speaking in tongues (such as during charismatic religious services).

For example, in the most famous alleged case of reincarnation, a Colorado woman named Virginia Tighe claimed in 1952 to have been a 19th century Irishwoman named Bridey Murphy in a previous life. Under hypnosis — and in an Irish accent — Tighe related memories of her previous existence in early 1800s in Cork, Ireland.

Yet the Bridey Murphy story soon fell apart under a close examination of the facts, as many of her claimed memories did not fit historical facts. Yet her defenders insisted that something unexplained must be afoot, because Tighe spoke with an Irish accent yet had never been to Ireland.

The mystery vanished (and, with it, the “best case” for reincarnation) when it was revealed that as a child Tighe often visited an Irish immigrant neighbor (named Bridie Murphy), from whom she picked up details about Ireland, along with an exposure to an authentic Irish accent.

In other cases, people who are suspected of being possessed by demons (and subsequently subjected to exorcisms) are sometimes said to speak in languages they never learned—even dead languages such as Aramaic, from the time of Jesus. Sensationalized depictions of this appear in films such as The Exorcist. Most people can pick up foreign accents of modern languages from TV and films, but what about dead languages? Is that possible?

As it turns out, no. In cases of xenoglossia, the unknown “language” that a person is speaking turns out to be no language at all. Though it may sound like a mysterious language—complete with convincing cadence and intonations—it is really only gibberish. Yet xenoglossia or glossolalia speakers are not necessarily faking.

Dr. Karen Stollznow, a linguist and researcher at the University of California, Berkeley, explains that “though glossolalia is the utterance of feigned language, this is not to say the subject intends to deceive. Instead, this phenomenon is more psychological than linguistic (a kind of localized mass hysteria). MRI studies have shown that when people speak in tongues they are using the emotion parts of the brain, rather than the linguistic centers.”

As for the claims that modern folks suddenly begin speaking fluently in ancient tongues they’ve never heard, these reports are always unverified. Stollznow adds, “It would be very, very easy for any halfway competent historical linguist to determine whether a case of speaking in tongues is cognitive access to a foreign language known to the subject, or if they’re talking gobbledygook.”