Mutual intelligibility and similarity of Chinese dialects

Distance between languages is used as a criterion when arguing about genealogical relationships between languages. The more languages resemble each other, the more likely they are derived from the same parent language, i.e., belong to the same language family. However, it is difficult to quantify the distance between languages one-dimensionally since languages differ along many structural dimensions (e.g. phonetics, phonology, morphology, syntax). It is unclear how the various dimensions should be weighed against each other. Therefore, we select a single criterion — mutual intelligibility. Mutual intelligibility is an overall criterion that may tell us in a psychologically relevant way whether two languages are similar/close. Useful work on structural measures of difference between related languages has been done, for instance, at Stanford University (for Gaelic Irish dialects, cf. Kessler 1995) and at the University of Groningen (for Dutch and Norwegian dialects, Heeringa 2004), using the Levenshtein distance measure. This is a similarity metric that computes the mean number of string operations needed to convert the phonetic transcription of a word in one language (variety) to its counterpart in another language (variety). This measure was then used to build a tree structure (through hierarchical cluster analysis) which largely matched the language family tree as constructed by linguists.