In their first months, bottlenose dolphins develop a unique 'signature whistle' that they often keep for life. Studies in 2006 and 2013 showed they recognise these signatures even when played in a synthetic voice, and respond when they hear a copy of their own whistle. It's one of the closest things to a personal name in the animal world.
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.