Around 1260, King Louis IX founded a hospice in Paris for 300 poor blind people. It was called the Quinze-Vingts: fifteen twenties. Medieval French often counted in scores, saying 'six-vingts', six twenties, for 120. In everyday French, only 'quatre-vingts', four twenties, survives for 80. The institution still exists today as the Quinze-Vingts National Ophthalmology Hospital in Paris.
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.