The document discusses three hypotheses about language acquisition: 1) The Innateness Hypothesis proposes that humans are pre-wired to acquire language and that the type of language is also determined. 2) The Critical Age Hypothesis suggests there is a critical period for language learning where it occurs quickly and easily, after which grammar becomes more difficult to acquire. Cases of isolated children support this. 3) The poverty of stimulus hypothesis notes that children seem to know aspects of grammar without being taught, and they don't produce ungrammatical sentences, indicating the influence of Universal Grammar.