Curvilinear principle

[1] First proposed by William Labov,[2] the curvilinear principle departs from traditional nineteenth century notions that language change generally originates in the highest or lowest classes of society.

[4] 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.

He studied a series of "new and vigorous" vowel changes, including the fronting and raising of (aw) and (ey) and the centralization of (ay).

[6] The distribution of linguistic variation in Trudgill's study thus abides by the curvilinear principle because members of the central classes led the change.