Does the use of two languages by bilinguals inevitably bring about grammatical change? Does switching between languages serve as a catalyst in such change? It is widely held that linguistic code-switching inherently promotes grammatical convergence - languages becoming more similar to each other through contact; evidence for this, however, remains elusive. A model of how to study language contact scientifically, Bilingualism in the Community highlights variation patterns in speech, using a new bilingual corpus of English and Spanish spontaneously produced by the same speakers. Putting forward...