Curvilinear principle

In sociolinguistics, the curvilinear principle states that there is a tendency for linguistic change from below to originate from members of the central classes in a speech community's socioeconomic hierarchy, rather than from the outermost or exterior classes.

Defined by William Labov, the curvilinear principle departs from traditional nineteenth century notions that language change generally originates in the highest or lowest classes of society. Instead, it states that variant forms leading to language change are typically introduced and motivated by the intermediate groups—the upper-working class and lower-middle class.

The principle can be seen as one response to an important question in sociolinguistics known as the embedding problem, a problem "concerned with determining regular patterns in both the linguistic and the extra-linguistic context of change." In other words, the embedding problem seeks to identify other changes or factors that have a non-coincidental relationship with the actual linguistic change. The curvilinear principle identifies such a non-trivial factor by proposing that a speaker’s class can indicate the degree to which he or she motivates linguistic change.

The principle's name refers to the curvilinear correlation that results from plotting the variation of a linguistic variable with respect to the class of the speakers. Because the lowest and highest classes generally tend to use newly emerging forms less frequently than central classes, data points representing variable usage resemble a concave curve when connected on a graph.

In The Philadelphia study, William Labov examined a series of linguistic variables in various stages of speech integration in order to evaluate whether the interior classes were, in fact, the innovators of linguistic change. In order to determine each speaker’s social position within the community, Labov created a socioeconomic status index based on education and occupation, each ranked on levels from 0 to 6, where 6 was the highest level of education or occupation. He studied a series of “new and vigorous” vowel changes, including the fronting and raising of (aw) and (ey) and the centralization of (ay). The research found that members of the upper working class and lower middle class used these variables more frequently than members of either the lower or upper class. This corroborated his curvilinear hypothesis because the middle classes were leading the use of these "new and vigorous" linguistic changes.

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