Who is the researcher that developed nativist approach and universal grammar to explain how children learn their language skills?

The researcher who developed the nativist approach and universal grammar to explain language acquisition is Noam Chomsky.

Chomsky's theory posits that humans are born with an innate capacity for language, a "language acquisition device" (LAD), which contains the universal principles of grammar common to all languages. This innate knowledge allows children to quickly and easily learn the specific rules of their native language.