SIGNS OF CHANGE?

Variation should be considered as a constitutive property of language use. One finds considerable variability in the use of particular constructions within languages, and individual speakers, too, make variable use of the options offered in a language. This observation applies to grammatical aspects of a person's linguistic knowledge as well as to grammar-external ones, although the variation space of the former is arguably more limited than that of the latter. The nature and the extent of linguistic variation are an issue of crucial importance for studies striving for insights into how grammars change over time: in linguistic ontogenesis, in first language (L1) acquisition, in studies of development across generations in diachronic linguistics, or in cases of language attrition or loss. Such endeavours to investigate grammatical change are typically based on comparisons of linguistic samples gathered at different points in time, and variation across samples is interpreted as a plausible indication of change over time, although this need not necessarily be the case, for variability across speech samples can be caused by other factors as well.

Native speakers are able to explore, to a larger or to a lesser degree, the variation space defined by situational (register), social (sociolectal) and even regional (dialectal) varieties of their language. It can be argued that in doing so they switch between varieties in much the same way as bilingual speakers switch between their languages. Consequently, the observed variability reflects alternations in the use of such varieties rather than diachronic change within a lect, although each of them is, of course, subject to change over time – the fourth dimension of the variation space.

In this book, we intend to pursue this last issue, change over time. We must therefore ask how it is possible to determine whether variability in use indeed reflects changes of this sort. In fact, since we are almost exclusively concerned with the question of how to account for changes in grammatical systems underlying language use, focusing on morphosyntactic constructions, the crucial question is whether instances of variation observed in language use actually indicate variation within a linguistic system rather than, for example, switching between systems, as illustrated by the possibility of alternate uses of lects.