Shepherds on La Gomera in the Canary Islands communicate across long distances and over rough terrain with shrill whistles that represent Spanish word syllables. For example, those who know this “Silbo” language and are separated by a ravine can transmit a message like, “Meet you at the hilltop at three o’clock.” A team of Spanish and American psychologists studying Silbo has found that the whistlers’ brains treat the sounds as language, whereas the brains of Spaniards who do not know Silbo do not. This is clear evidence, says David Corina of the University of Washington, that “the language-processing regions of the human brain can adapt to a surprisingly wide range of signaling forms.”

Corina and Manuel Carreiras of the University of La Laguna in the Canaries used functional neuroimaging to watch the subjects’ brains while they listened to recorded Silbo, spoken Spanish and nonsense whistling. The temporal regions of the left hemisphere associated with spoken-language function became active when whistlers heard Silbo sentences, which did not happen for Spanish speakers who do not understand Silbo. Unfortunately, few shepherds live on La Gomera today, and most have cell phones. Silbo is dying out.