Hildegard of Bingen (1098–1179), nun, composer and scholar, left behind a strange glossary: the 'Lingua Ignota', the unknown language. It holds over a thousand invented words, glossed in Latin and sometimes German, for God, angels, body parts, plants and tools, along with a 23-letter alphabet of her own design. Nobody knows what it was for. It is one of the oldest known constructed languages.
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.