Noam Chomsky is an American linguist, philosopher, cognitive scientist, historical essayist, social critic, and political activist who is regarded as”the father of modern linguistics”. In 1957, Chomsky introduced the concept of language acquisition device (LAD) which was used to account for the language acquisition competence of human beings. He believed that the acquisition of the first language is the function of the human brain or an innate structure. The introduction of UG or Universal Grammar is also credited to Chomsky.

Chomsky believed that humans are born with:

1. LAD, a set of language learning tools.

2. LAD is an abstract part of the human mind which enables humans to acquire and produce language. 

3. Since they are equipped with LAD, children can acquire rules of a language through hypothesis testing

4. LAD transforms these rules into basic grammar. 

Universal Grammar is a theoretical concept propounded by Chomsky who states that, “the human brain contains an innate mental grammar that helps humans acquire language.” According to Chomsky, “the LAD explains why children seem to have the innate ability to acquire a language and accounts for why no explicit teaching is required for a child to acquire a language.” He stated that LAD is, “separate from other faculties of cognitive activity….Input is needed, but only to ‘trigger’ the operation of the language acquisition device.”

About Universal Grammar, Nowak et al. summarize:

“Children acquire their mental grammar spontaneously and without formal training. Children of the same speech community reliably learn the same grammar. Exactly how mental grammar comes into a child’s mind is a puzzle. Children have to deduce the rules of their native language from sample sentences they receive from their parents and others. This information is insufficient for uniquely determining the underlying grammatical principles (4). Linguists call this phenomenon the “poverty of stimulus” (5) or the “paradox of language acquisition” (6). The proposed solution is universal grammar.”

Chomsky rejected Skinner’s Behaviorism Theory because he felt that there is more to language acquisition than stimulus-response. He rejected the idea of operant conditioning due to the poverty of the stimulus. He also believed that the theory was lacking and believed that innateness was an important aspect of language acquisition.