Final answer:
The Critical Period hypothesis suggests there's a specific window for optimal language acquisition. Evidence includes case studies of individuals like Genie, who experienced language deprivation, and research.
Step-by-step explanation:
Two arguments in favor of the Critical Period hypothesis in language acquisition are the following:
- Case studies of language deprivation such as the well-known case of Genie, provide empirical evidence that there is a limited window for language acquisition. After being isolated without linguistic input for most of her childhood, Genie's subsequent language development was stunted, particularly in the aspect of grammar, indicating a potential critical period for grammar acquisition.
- Age-related maturational constraints are evident in studies like those by Johnson and Newport (1989), which show that the ability to learn a second language with native-like proficiency declines after puberty. This decline suggests that there is an optimal period during which the neural plasticity required for language acquisition is at its peak.