The nativist theory, championed by Noam Chomsky, posits that humans are born with an innate capacity for language acquisition, equipped with a "language acquisition device" (LAD) in their brains. This framework suggests that children possess an inborn biological predisposition to learn language, allowing them to rapidly acquire complex grammatical structures even with limited exposure. This theory highlights the critical period hypothesis, emphasizing a specific window for effective language learning, and is supported by observations of effortless language acquisition and the "poverty of the stimulus."