Grammar as a Maturational Controlled Behavior: Minimality in Development and Impairment

In his seminal book on the Biological Foundations of Language, Eric Lenneberg proposed that a critical period similar to the one necessary for maturational controlled behaviors applies also to language acquisition (Lenneberg 1967). The notion of a critical period, a maturational stage during which the nervous system is sensitive to specific aspects of the environment, has been considered crucial for language acquisition theories based on the assumption of a biologically predetermined language faculty that needs to be activated by favourable internal and environmental circumstances. Chomsky wrote: