7. Language-internal variation
According to standard procedures in sociolinguistics, testing mutual intelligibility between closely related speech varieties is one important way of finding out whether the varieties are to be treated as dialects of the same language or as distinct languages. Determining whether one is dealing with two distinct languages or two dialects of one and the same language, however, is a considerable problem for synchronic linguistics. As shown in a classic sociolinguistic contribution by Wolff (1959) for two members of the Ijo family (southern Nigeria), testing intelligibility sometimes raises problems, because judgements may also depend on speakers’ attitudes and their willingness to understand the other variety. Also, intelligibility judgments may be determined by the degree of exposure to other lects, as the collection of differences between individuals (idiolects), or differences between social groups (sociolects) as well as regional differences (dialects) are sometimes called. It is the study of this latter aspect of language, in particular dialectal differences, which shall occupy us in the present chapter.