Language develops through a process of innate abilities interacting with environmental influences. Children are born with an innate language acquisition device that gives them the ability to learn the structure of any human language. According to Chomsky, this includes a universal grammar consisting of principles common to all languages. Vygotsky also viewed language development as a social process, where children acquire language abilities through interaction with others. Stages of language acquisition begin with pre-linguistic sounds and progress to single words, word combinations, and eventually grammatically complex speech over the first 5-6 years of life.