Distinguishing Contact-Induced Change from Language Drift in Genetically Related Languages

Languages evolve, undergoing repeated small changes, some with permanent effect and some not. Changes affecting a language may be independent or contactinduced. Independent changes arise internally or, if externally, from non-linguistic causes. En masse, such changes cause isolated languages to drift apart in lexical form and grammatical structure. Contactinduced changes can happen when languages share speakers, or when their speakers are in contact. Frequently, languages in contact are related, having a common ancestor from which they still retain visible structure. This relatedness makes it difficult to distinguish contact-induced change from inherited similarities. In this paper, we present a simulation of contact-induced change. We show that it is possible to distinguish contact-induced change from independent change given (a) enough data, and (b) that the contactinduced change is strong enough. For a particular model, we determine how much data is enough to distinguish these two cases at p < 0.05.