Bilingualism-induced language change: what can change, when, and why?

Abstract Contact between languages has become increasingly recognized as a major source of historical change, as linguistic properties are introduced from one language into another. Yet contact does not necessarily lead to such changes. In fact, arguably most of the properties that contrast between two languages in contact at a given place and time do not change. This paper argues that historical and contact linguistics should now look more systematically at different kinds of bilingualism rather than contact per se and should incorporate recent sociolinguistic and psycholinguistic findings from this literature, since these can help us understand both when change occurs and when it does not. In this context we build on the general model of bilingualism, CASP (short for “complex adaptive system principles”), proposed by Filipović and Hawkins and explore its predictions for whether and when changes will occur in one or the other language of a bilingual. In the event that the relevant speech community comprises monolinguals in addition to bilinguals, these changes may then spread to the wider community when social and demographic circumstances favor this. The paper gives illustrative data supporting CASP’s predictions for change in both language usage and grammar among bilinguals.