Japanese Lexical Variation Explained by Historical Contact Patterns

We assemble a set of methodologies using theories in variationist linguistic and GIScience, and tools used in historical GIS to analyse spatial variation in Japanese dialectal lexicon. Based on historical dialect atlas data, we calculate a linguistic distance matrix across survey localities. The linguistic variation expressed through this distance is contrasted with several distance based measurements utilised to estimate the potential of language contact across Japan historically and at present. Besides, administrative boundaries are tested for their separation effect. Aggregate association measures within linguistic variation can challenge previous notions of dialect area formation. Depending on local geographies in spatial subsets, great circle distance, travel distance and travel times explain a similar proportion of the variance in dialectal variation despite the limitations of the latter two. While they explain the majority, two further contact estimations have lower explanatory power: least cost paths implemented to model contact before the industrial revolution, based on DEM and seafaring, and a linguistic influence index based on the law of gravity. Historical domain boundaries and present day prefecture boundaries are found to have a substantial effect on dialectal variation. However, the interplay of boundaries and distance is yet to be identified. We claim that a similar methodology can address spatial variation in other digital humanities, given a similar spatial and attribute granularity.