Critical Period Effects

The Robustness of Critical Period Effects in Second Language Acquisition by Robert M. DeKeyser (2000)

New Words
-His articles provided the main impetus for change.
-The town has a sizeable Sikh population.
-Virtually all students will be exempt from the tax.

Main points
Fundamental Difference Hypothesis (Bley-Vroman, 1988)
Adults need to consider a structure of a second language and to use verbal-analytic problem-solving mechanisms for explicit learning because they have mostly lost the ability to learn it. On the other hand, children learn a language through language-specific mechanisms of implicit learning. The hypothesis suggests only adults who have a high level of verbal ability will succeed in getting a second language competence.
Critical Period Hypothesis (Lenneberg, 1967)
-Those who are older than a certain age (17) are worse at learning both pronunciation and grammar of a second language than younger people.
-The concept is controversial.

Conclusion
-Fundamental Difference Hypothesis is correct.
-Language-learning aptitude is important to succeed in acquiring a second language.
-Ideal age for language learning exists.