What makes speakers omit pitch accents? An experiment

The present paper reports on an experiment which was set up to examine whether we can make a speaker either accent or de-accent particular words by systematically varying the objective probability that a particular referent will be mentioned (and therewith the referent's predictability for speaker and listener). In the experiment each of 24 speakers was asked to watch a visual display, showing a very simple configuration of letter symbols, and to describe orally each change in the current configuration to a listener. By manipulating the letter configurations shown on the display, the objective probability that the speaker would mention a particular letter could be controlled. Letters could either move around on the screen (moving letters) or remain fixed and serve as spatial reference points (fixed letters). Objective probabilities were 0.5 and 1 for both moving letters and fixed letters. The main findings were the following: (1) When a referent is fully predictable to speaker and listener there is a high proportion of ellipsis, particularly for the moving letter, which was always referred to from subject position. (2) The probability that a word referring to a letter will be accented appears not to be immediately controlled by the predictability of the referent. The controlling factor is rather the preceding linguistic context. More specifically, the probability of accenting, being close to 1 the first time a specific referent is mentioned, sharply decreases when the same referent is mentioned for the second time in a row, and decreases again when this same referent is mentioned three or more times in a row. However, as soon as the competing referent is mentioned once, in the same role (moving or fixed letter), the probability of accenting jumps up again. (3) The probability of accenting is systematically lower for the moving letters in subject position (average 0.32) than for the fixed letters in predicate position (average 0.52). In view of these findings, de-accenting, defined as conspicuously omitting an accent on a word that, for grammatical reasons, otherwise would have been accented, is interpreted as a device which can be used by a cooperative speaker for helping the listener to find the intended referent as easily and quickly as possible. It is supposed that speakers not using this device systematically give their listeners a harder time.