The aim of this presentation is to find out what mechanisms or principles are involved in grammaticalization, in order to gain a better understanding of what drives the process. Grammaticalization has usually been looked at from a diachronic perspective, which focuses on small shifts on the level of language output. Here, the process will be considered from a synchronic viewpoint, examining the circumstances under which it takes place. Special attention will be paid to speaker/hearers, who initiate the process and are ultimately responsible for the spread of any new grammatical construction. It is argued that the factors that influence processing must be the same in both language acquisition and change. Iconicity, especially in the form of (structural) analogy, is considered to be a basic and domain-independent principle that steers language learners and remains active in the language use of adult speakers and in change.
