Produced Speech Rhythm Depends on Predictability of Stress Patterns

If speakers repeat a phrase, their speech tends to be highly rhythmical. In a similar task without repetition, no such rhythmicity was found. This study investigates whether stress predictability, varied between tasks, affects speech rhythm. Results show that a regular speech rhythm emerges in repeated phrases (with highly predictable stress pattern), but not in other tasks without repetition (medium and low predictability of stress). For all tasks, the presence or absence of stress shift in a phrase partly depends on its global rhythmical pattern. A clear speech rhythm emerges only if a speaker can predict the upcoming stress pattern, and use this information to optimize the temporal organization of his output speech.