To Predict or to Memorize: Prominence in Inaugural Addresses

The assignment of phrasal prominence has been variously attributed to syntactic structure, part of speech, predictability, informativity, and speaker's intent. A recent account asserts that prominence is memorized on a by-word basis as Accent Ratio (AR), the likelihood that a word is accented (Nenkova et al. 2007). We examined whether AR outperforms the traditional predictors, in particular syntax and informativity, and if not, whether the traditional predictors shed light on the variance left unexplained by AR. We used a corpus of spoken American English consisting of the first inaugural addresses of six recent American presidents, hand-annotated for stress by two native English speakers. Regression models fitted to the data revealed that AR, syntax, and informativity all independently matter. Dividing the data into high-prominence and low-prominence tokens further revealed that AR and informativity are significant among low-prominence words, but only syntax is significant among high-prominence words. We conclude that although AR is a highly successful predictor, certain aspects of phrasal prominence require reference to syntax and informativity