What cycles when and why
Certain kinds of grammatical markers show heightened propensities for turnover cross-linguistically. Some, like negatives, are widespread, while others, such as distributives, are rarer. Several factors might underlie these propensities. Most cycles involve two sets of processes: grammaticalization and renewal. Grammaticalization processes, which can result in phonological erosion, semantic generalization and abstraction, and pragmatic weakening, are generally driven by frequency. The resulting form/function mismatches can trigger renewal, stimulated by expressive need and the availability of resources for new markers. These factors are first investigated in negative, demonstrative, pronominal, reflexive, and distributive cycles from languages of the Iroquoian family, indigenous to eastern North America. Another potential factor, language contact, is then explored, with examples from languages indigenous to western North America.