Hyperpolyglots

Michael Erard's review mentions Giuseppe Mezzofanti, "the nineteenth-century Bolognese cardinal who was reputed to speak between thirty and seventy languages, ranging from Chaldaean to Algonquin" — Babel No More: The Search for the World's Most Extraordinary Language Learners. More:

He spoke them so well, and with such a feather-light foreign accent, according to his Irish biographer, that English visitors mistook him for their countryman Cardinal Charles Acton. (They also said he spoke as if reading from The Spectator.) His ability to learn a language in a matter of days or hours was so devilishly impressive that one suspects Mezzofanti pursued the cardinalate in part to shelter himself from accusations that he had bought the talent from Satan himself.

Today, the author suggests, "no one succeeds in switching from Abkhaz to Quechua to Javanese in the way Mezzofanti was said to," but mentions someone I almost knew, a Catholic who used to live across town from me in Pohang teaching at the Protestant Handong Global University, and whose book, Historical, Literary, and Cultural Approach to the Korean Language, the best on the subject, graces my shelf:

Among the more impressive workhorses is Alexander Arguelles, who, at the time of his first meeting with Erard, is an unemployed academic and jogging enthusiast living in California. Arguelles reads novels in Dutch, writes and reads classical Arabic, and translates Korean for cash on the side. But he also spends twelve hours every day learning languages and obsessively cataloguing his progress. In his case, the hyperpolyglottism appears to be simply compulsive behavior.