Here's why he believes this:
* Poverty of the Stimulus Argument: Chomsky argues that the input children receive from their environment (the language they hear spoken around them) is insufficient to explain the complexity of the languages they eventually learn. The input is often incomplete, ungrammatical, and lacks crucial information. This leads to the "poverty of the stimulus" argument, suggesting that children must rely on innate knowledge to fill in the gaps.
* Universality of Language: All languages share fundamental structural properties, like syntax and grammar. Chomsky believes this universality points to an innate blueprint for language acquisition.
* Rapid Language Acquisition: Children acquire language at an incredibly fast rate, often mastering the basics of their native language by age 5. This rapid learning suggests a biological predisposition for language.
However, Chomsky does acknowledge the importance of environmental factors. While UG provides the foundation for language, it needs to be triggered and shaped by interaction with the environment. Children learn the specific vocabulary, sounds, and grammar of their native language through exposure and interaction.
In summary, Chomsky's view on language acquisition is nativist, emphasizing the role of innate factors. However, he acknowledges the role of the environment in shaping and refining the language faculty.
It's important to note that Chomsky's theory has been both influential and controversial. There are alternative theories of language acquisition, such as connectionist models and usage-based theories, which emphasize the role of learning and experience more strongly. The debate about the relative contributions of innate and environmental factors continues to be an active area of research in linguistics and cognitive science.