In India, Nigeria or the Philippines, juggling two, three or four languages every day is completely ordinary. Specialists such as psycholinguist François Grosjean estimate that more than half of humanity is bilingual or multilingual. The 'one country, one language, monolingual citizens' model is largely a fairly recent European habit.
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.