Unraveling the Overall Picture of Japanese Dialect Variation: What Factors Shape the Big Picture?

We studied the Japanese dialect by calculating aggregated PMI Levenshtein distances among local Japanese dialects using data from 2400 locations and 141 items from the Linguistic Atlas of Japan Database (LAJDB). Through factor analysis, we found the latent linguistic variables underlying the aggregated distances. We found two factors, the first of which reflects a division into five groups, and the second of which reflects the long-standing East/West cultural contrast in mainland Japan, also known as the AB division. In the latter division, the eastern group includes the Okinawa islands. We paid special attention to the Tokyo dialect, which is associated with Standard Japanese. In a second factor analysis, only distances to the Tokyo dialect were considered. Although the patterns represented by the four factors vary, they consistently show that dialects geographically closer to Tokyo are more similar to the Tokyo dialect. Additionally, the first three factors reflected the similarity of the Hokkaido varieties to Tokyo’s local dialect. The results of the factor analyses were linked back to the individual variation patterns of the 141 items. A more precise analysis of Tokyo’s position within the Japanese dialect continuum revealed that it is situated within a region of local dialects characterized by relatively small average linguistic distances to other dialects. This area includes the more central area of mainland Japan and Hokkaido. When the influence of geographical distance is filtered out, only the local dialects of Hokkaido remain as dialects with the smallest average distance to other local dialects. Additionally, we observed that dialects geographically close to Tokyo are most closely related to it. However, when we again use distances that are controlled for geographical distance, the local dialects on Hokkaido stand out as being very related to the Tokyo dialect. This probably indicates that the Tokyo dialect has had a relatively large influence on Hokkaido.