Some errors produced by SL learners are due to the actual strategies that the learners use. These can be such techniques as imitating others, guessing, hyperregularization, etc. This will force them to improvise. They will have to circumlocute, coin words, approximate, etc. Selinker and Lamendella distinguish between fossilization and and stabilization of interlanguage terms.
Fossilization refers to permanent retention of non-native interlanguage forms.
Fossilization is more likely to occur if the students are not motivated to change. There have been several studies of native-speaker reactions to interlanguage. Irritation refers to the effect that the interlanguage has on the native speakers Vocabulary errors seem to be the most easily recognizable to native speakers. Thus, global errors should be corrected while local ones, perhaps, should not be. Cohen suggests a comprehensive system for error selection, with 4 areas of analysis 1.