Fossilization (language acquisition)

Fossilization, in linguistics and second language acquisition (SLA), refers to the often-observed loss of progress in the acquisition of a second language (L2), following a period where learning occurred.

The number of second language learners who are considered to develop nativelike fluency in an L2 is generally assumed to be small. At some point in the learner's path of development, no further learning appears possible, with their performance apparently impervious to both further exposure to the L2 and explicit correction of errors. Because the L2 now appears 'set in stone', the term fossilization was used to describe this point.

There is no particular level that can be identified at which learners appear to fossilize, though it is more often observed in intermediate proficiency levels and above. A famous case study concerns 'Patty', a Chinese woman in Canada studied for many years by linguist Donna Lardiere. Patty has an extremely high level of comprehension of English, but her spoken language is typically missing inflections such as the -s applied to the verb in sentences like she dances. These errors seem to resist correction and have not disappeared despite many years in an English-language community.

Whether fossilization is inevitable, very likely or avoidable has long been discussed in SLA. While some scholars have argued that nativelike fluency in an L2 is not possible beyond a certain age (the critical period hypothesis), others argue that fossilization is a result of a learning environment that is far from ideal, or a mind that has reached subconscious conclusions that are difficult to unlearn, meaning that a nativelike level of ultimate attainment is possible in the right conditions. The general trend has been for the estimated proportion of learners able to master an L2 in such a way as to be indistinguishable from a native speaker to have increased over the years.