This is known as the critical period hypothesis.

He claimed that children before their critical period were less severely impaired by brain damage.

The critical period hypothesis ..

GK: It is a valid criticism that degrowth is stuck to the modernist and Western perception of a linear time. As I have argued elsewhere though (in my article ‘The utopianism of degrowth’ with Hug March) the spatio-temporal dialectics of degrowth are interesting. The idea is that we take seeds from the past to produce the future now. Think, for example, of urban gardens. These are a commons. Commons is an idea coming from the pre-capitalist past. But at the same time when we are working on an urban garden in common we are prefiguring a different future, now and in a concrete space. The linear evolution of time where the future follows the past and is an improvement of it, somewhat breaks down in this way. I don’t think it becomes a circle though, and maybe that’s fine.

Phonological acquisition seems to be more sensitive to the critical period than that of grammar.

A concept of 'critical period' for language acquisition

That is to say, instead of using a label of age as the critical period for language acquisition, one would be more correct to say the critical period for language acquisition occurs between certain stages of development.

'A critical Period for Learning to Pronounce Foreign Language?' Applied Linguistics.

Period hypothesis for second language acquisition david birdsong... the case of chelsea: a new test case of the critical period for language acquisition.

A time to speak: a psycholinguistic inquiry into the critical period for human speech.

is known as the critical period hypothesis.

This is another way of saying that conscious knowledge cannot penetrate your visual module or language module or any other subconscious module.

Basically, Fodor’s arguments are somewhat similar to that of Chomsky or the proponents of UG Theory in that the external input per se may not account for language acquisition and that language acquisition is genetically predetermined.

Critical Period Hypothesis & Language Acquisition by …

All of these criticisms of the past studies show how difficult it is to connect brain functions and language acquisition.Moreover, the different methods for the research on the CPH have also resulted in varieties of inconsistencies.

Case Study of Isabelle - Critical Period Hypothesis

However, a recent survey disputes his claim because children with Down's syndrome have a build-in endpoint to their ability (Gleitman 1984).Secondly, the theory of brain's lateralization at the age of two, with the critical period set by Lenneberg (1967), is also criticized.

Critical Period Hypothesis: Children with no language

It was recorded that her syntax created sentences such as 'the woman is bus the going' and 'banana the eat.'All these cases of children reared in isolated environments reveal the difficulties of learning a language after the critical period.

The Critical Period Hypothesis ..

By the age of eight and one half Isabelle was not easily distinguishable from ordinary children of her age.It is reasonable to consider that she was able to acquire her language because she started learning before the critical period came to an end.The second case was Genie, who was found at the age of about fourteen (Curtiss, Fromkin, Krashen, Rigler, and Rigler 1974).