Sally Thomason gave a plenary talk, "Contact-induced language change and typological congruence", at the 38th Annual Meeting of the Berkeley Linguistics Society in February; she gave a revised version of this talk at a New York University colloquium on March 2.
Questions are frequently raised about whether typological congruence facilitates contact-induced language change and, conversely, about whether certain kinds of contact phenomena are rare or even nonexistent in situations where the languages in contact are very dissimilar typologically. This paper provides tentative answers to these questions. I argue that although there is no simple correlation like "more congruent languages = more feature transfer", it is true that some features -- perhaps most notably in the inflectional morphology -- are more easily transferred between typologically congruent languages. However, attitudinal factors may counteract any tendency toward increased homeogenity in the structures of (for instance) closely-related languages in contact, so that one cannot predict with any confidence that more similar languages will become even more similar over time. Moreover, profound contact-induced changes often affect typologically dissimilar languages, especially when the agents of change are fluent in both the source language and the receiving language. And finally, when speakers in a contact situation deliberately change their language(s), there seems to be no established effect of typological congruence on the process of change.