Acquisition and Learning
Definition
Ellis (1997:3) defines second language acquisition as "the way people learn a language other than their mother tongue, inside or outside a classroom", thus conflating the two terms acquisition and learning. Other writers however, have distinguished between the two, defining them so that:
Acquisition refers to the process of assimilating a language non-consciously through exposure to that language rather than by formal instruction, conscious understanding of rules etc (learning).
Example : A child acquires, rather than learns, their L1.
The Acquisition/Learning Hypothesis
One of the five hypotheses in the Monitor Model proposed by Krashen in his work in the 70s and 80s. Krashen suggested that, in the L2 situation, acquisition and learning were two distinct neurological processes. He also claimed (and this is where the hypothesis becomes most controversial) that only acquired language is available for fluent, spontaneous use and that acquisition cannot be affected by learning - ie "learning" the language will not replace or speed up acquisitional processes. He suggested that the ability to acquire language is not lost at puberty, as advocates of the critical period hypothesis would claim, but remains possible throughout adulthood.
Criticisms :
Many writers would argue that, on the contrary, conscious "noticing" and deep cognitive processing is not only an aid to L2 acquisition but also essential for it. Thus the two terms again merge, taking us back to Ellis' definition.
Further reading
Baker, C. and Prys Jones, S. Encyclopedia of Bilingualism and Second Language Acquisition
Ellis, R. Second Language Acquisition, OUP