William Labov has spent decades studying dialects of English in America, and what his studies reveal are results contrary to common assumptions about dialect in America.
Among those results is that, contrary to popular assumption, broadcast television and radio, and other mass media, are not causing dialect diversity to decrease. Dialects across large regions are not changing to become more alike, but in some ways more different. This includes Northern Inland, Midland, and Southern dialects. Changes in these dialects have progressed somewhat in step with each other--but not in the direction of becoming more similar. Sound changes have arisen and are still arising that produce misunderstandings between primary speakers of one dialect and another. Thinking of language as a means of communication, it seems unexpected that dialects would move further apart when speakers of those dialects are communicating directly with each other as well as consuming the same national media. Labov looks at what seem to be the causes of this seemingly strange development.
