Change and continuity in the functions of the American English modals

Analysis of over 5,000 tokens of modals in written representations of spoken American English since 1824 shows that there have been significant changes, in terms of both the modals used and the functions of modal expressions. Around the time of the Civil War, the modals must, should, may, and shall dropped drastically in frequency, and at the same time other modals, got to, have to, ought, better, can, and gonna, sharply increased in frequency. The “old” and “new” modals overlap in some general functions, representing obligation, possibility, and future tense. However, within these general functions, the “old” and “new” modals have been characteristically used for different specific types of functions: the “old” modals had usages associated with hierarchical social relationships, with people controlling the actions of other people, and with absolute judgments based upon social decorum, principle, and rules about societal expectations of certain types of people. The “new” modals, on the other hand, are more personal, being used to, for example, give advice to an equal, make an emotional request, offer help, or criticize one's interlocutor. The functional similarity of the various older modal functions as opposed to that of the newer modal functions suggests that the various changes noted all represent different aspects of a single change in the fundamental semantic parameters of the language.