Children are born knowing a Universal Grammar

Children acquire their first language(s) with the help of a Universal Grammar (UG), a set of rules that children are born knowing that govern how all human languages work. The innate presence of a UG in children's brains is the best way of explaining why children learn language in the way that they do as well as why typical children easily become fluent in their first language(s) without any formal teaching. There is a host of evidence to support the theory of Universal Grammar. First, humans are the only species that we know of that have language, so there must be something innately within us allowing us to learn language fully that is missing from other animals, plants, etc.^[2] Second, every language appears to share certain properties, and there are examples of distant, completely unrelated languages, like Japanese and Quechua, that look remarkably like one another.^[3] Third, if two children are exposed to different varieties of the same language--or even if one of the two has little to no exposure to certain sentence structures--both children will yield the same understanding of the language and its rules.^[2] Lastly, regardless of the culture in which a child is raised or the language(s) learned, all children go through the same stages of language learning in the same order.^[2] There have been many more arguments put forth in support of the UG hypothesis over the years, but the core point of all of them is this: even with minimal exposure and little to no correction and instruction, children learn language and its rules through their innate Universal Grammar.