In 1934, the second edition of Webster's New International Dictionary welcomed 'dord', defined as 'density' in physics and chemistry. The trouble: no such word exists. A slip reading 'D or d', meaning the abbreviation 'D or d' for density, had been filed as a word by mistake. In 1939, an editor noticed that 'dord' had no etymology and uncovered the blunder. Lexicographers call such intruders 'ghost words'.
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.