Dealing with ‘non-geographic’ lexical heterogeneity when deriving dialect maps from lexical data

In dialectometry several approaches exist to automatically generate dialect maps on the basis of calculated dissimilarities between locations (using survey data). Examples for Dutch are Heeringa (2004), who calculates dialect maps on the basis of aggregated phonetic dissimilarities, and Spruit (2008), who calculates dialect maps on the basis of aggregated syntactic dissimilarities. In both examples the automatically generated maps bare a strong resemblance to reference dialect maps compiled by expert dialectologists. However, obtaining similarly succesful results on the basis of lexical information has proved to be far more difficult, in spite of the existence of a long research tradition and the availability of authorative, well studied lexical dissimilary measures (most notably the gewichteter Identitätswert, Goebl 1984).