In this final chapter, we take a look at the possible sources or causes of linguistic change. Of course, we have discussed the causes of change throughout the book, but in this chapter we address the issue of causes more directly and more generally. In broad outline, we consider factors internal to language as causes of change in contrast to external causes, in particular the influence of other languages. In this way, Section 11.1 on internal sources contrasts with Sections 11.2 and 11.3, which deal with situations of languages in contact. In Section 11.1 we will look briefly at some theoretical approaches that address issues of diachronic change, in particular Naturalness Theory in Section 11.1.1 and generative theories in Section 11.1.2. In Section 11.1.3 we consider briefly whether child language is a plausible source of linguistic change. After the sections on language contact, in Section 11.4 we consider the idea that language is a complex adaptive system, in which dynamic factors inherent in the speaker, listener, and context produce change.
Internal sources: language use
This section will first review the approach presented in the previous chapters, drawing together some common mechanisms and general patterns that have been identified across the different types of change. The approach taken here recognizes the role of language use in creating and propagating change and conforms to usage-based theory so we will call it the usage-based approach. Next, the discussion turns to other proposals, in particular that coming from Naturalness Theory, which proposes that language structures change to become more natural or less marked. Finally, we consider the generative approach, which hypothesizes that language change occurs in the language acquisition process.