In 2018, researchers from MIT and Harvard analysed an online English grammar quiz taken by nearly 670,000 people. Their conclusion: the ability to learn a new language's grammar stays strong until about age 17, then declines. But to reach native-like fluency, it's best to start before about 10, because the learning itself takes years. It's never too late to learn, but perfection gets rarer. A 2022 reanalysis, however, disputes such a sharp cut-off.
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.