In 1911, French ear, nose and throat doctor Étienne Lombard described a reflex: as background noise rises, we speak louder, without realising it. He used it to unmask people faking deafness, who raised their voices despite themselves. We now know the voice also rises in pitch and vowels get longer. This 'Lombard effect' also exists in many animals: birds, bats, monkeys and whales all call louder amid the din.
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.