“Sometimes changes in language behaviour do not seem to be explainable in terms of a gradual build-up of fluency through practice. These changes have been described in terms of restructuring (McLaughlin 1990). They seem to be based on some qualitative change in the learner’s knowledge. Restructuring may account for what appear to be bursts of progress, when learners suddenly seem to ‘put it all together’, even though they have not had any new instruction or apparently relevant exposure to the language. It may also explain apparent backsliding, when a systematic aspect of a learner’s language incorporates too much or incorporates the wrong things. For example, as we saw in Chapter 2, when a learner finally masters the use of the regular -ed ending to show past tense, irregular verbs that had previously been used correctly may be affected. Thus, after months of saying ‘I saw a film’, the learner may say ‘I seed’ or even ‘I sawed’. Such overgeneralization errors are not based on practice of those specific items but rather on their integration into a general pattern.”