The English go future, a quintessential example of grammaticalization, has shown layering with will since at least 1490. To date, most synchronic evidence for this development comes from dialects where be going to represents a sizable proportion of the future temporal reference system. However, in the United Kingdom in the late twentieth century there were still dialects where be going to was only beginning to make inroads, representing a mere 10–15 per cent of future contexts. These varieties offer an effective view of the early stages of grammatical change.
Statistical analysis of nearly 5,000 variable contexts reveals that the use of be going to is increasing across generations, but at different rates, depending on location and orientation to mainstream norms. Major patterns of use mirror previous findings: be going to is favoured for subordinate clauses. However, other widely reported constraints conditioning be going to are radically different across age groups, exposing contrasts between incipient vs later stages of grammaticalization. In the most conservative dialects be going to is strongly correlated with negatives and questions especially in the first person singular. This suggests that these contexts may have been the ‘trigger’ environments for redistribution of meaning of the incoming grammatical form (Hopper & Traugott 1993: 85). The fact that strong effects of negatives and questions endure in contemporary urban varieties (Torres-Cacoullos & Walker 2009) confirms that grammaticalization begins in very specific syntactic contexts, and impacts on the system for generations to come. In contrast, other reported constraints – resistance of be going to in the first person singular and extension to inanimates and far future readings – emerge across generations, suggesting they are later developments.
Taken together, these findings demonstrate how synchronic dialects show us incremental steps in the grammaticalization process. Comparative sociolinguistic analysis thus offers insights into which patterns define the point of grammaticalization itself; which derive from systemic processes; which can be attributed to discourse routines and collocations; and how these factors converge in shaping the evolution of grammar.