In Kuşköy, a mountain village in northern Turkey, people talk across valleys by whistling Turkish. A 2015 study showed that whistled Turkish draws on both hemispheres fairly evenly, whereas spoken Turkish relies mostly on the left. The physical form of the signal, it turns out, matters to the brain.
Speech has no gaps between words. In 1996, researchers played 8-month-old babies a continuous stream of made-up syllables for just two minutes. The infants picked out the 'words' by tracking which syllables tend to follow one another. That's probability calculation, done without a calculator or any visible effort.
On La Gomera, Silbo Gomero turns Spanish into whistles that carry for several kilometres across deep ravines. Once close to vanishing, it has been taught in schools since 1999 and was added to UNESCO's Intangible Cultural Heritage list in 2009. Researchers count around 70 whistled languages around the world.