Children acquire language spontaneously without being explicitly taught how. Their mastery of sounds passes through stages determined by a progression from unmarked to more marked sounds, unmarked ones also being those most commonly found in languages and least likely to erode over time, as discovered by founding linguist Roman Jakobson. Their mastery of other aspects of grammar proceeds along with their ability to master rules, rather than simply memorize. It was once thought that children learned to speak simply by imitating adults: They hear adults saying words, and then they pick up words. However, modern linguists have found that it is something apparently innate to the species, and thus it proceeds according to basic aspects of ...