I just finished William Labov’s Principles of Linguistic Change: Social Factors, which is a detective story. No, really. You don’t expect a linguistic tome to have the literary quality of suspense, but this book does. It’s organized around the central puzzler of historical linguistics: why does language change? Why do people bother with sound changes, especially when everyone agrees that they’re destructive if not positively evil? It takes the whole book to create a framework to answer the question.
Rather than keep you in suspense, I’ll quote Mark’s summary:
◘ The leaders of sound change are almost always women; they’re often a generation ahead of the men.
◘ Women keep advancing a sound change in a linear fashion; men’s advance is stepwise. The obvious interpretation is that men don’t pick up the change from their contemporaries, but from their mothers.
◘ There’s a typical curvilinear function of class: neither the lower class nor the upper class are in the forefront of change, but those in the middle– even more specifically, the upper working class.
◘ Nonstandard variants often peak in adolescence. So older speakers may retreat from a change.
◘ There’s only a very small contribution from ethnicity or neighborhood (except to the degree that these correlate with class).
◘ A phoneme doesn’t change all at once; some words are leaders, some laggards. For some reason, the tensing of short a in Philadelphia strongly affected the word planet, while Janet remained lax. (This is reminiscent of the effect of Trojan horse words in gender change.)
He also “was able to identify individuals who were in the forefront of sound changes in Philadelphia”; go to the link for the exciting details. (Via Sentence first.)