Prosodic adaptations to pitch perturbation in running speech.

PURPOSE: A feedback perturbation paradigm was used to investigate whether prosodic cues are controlled independently or in an integrated fashion during sentence production.
METHOD: Twenty-one healthy speakers of American English were asked to produce sentences with emphatic stress while receiving real-time auditory feedback of their productions. The fundamental frequency (F0) of the stressed word in each 4-word sentence was selectively shifted in a sensorimotor adaptation protocol. Speakers experienced either an upward or a downward shift of the stressed word, which gradually altered the perceived stress of the sentence.
RESULTS: Participants in the Up and Down groups adapted to F0 shifts by altering the contrast between stressed and unstressed words differentially, such that the two groups deviated from each other in the perturbation phase. Furthermore, selective F0 perturbation in sentences with emphatic stress resulted in compensatory changes in both F0 and intensity.
CONCLUSIONS: Present findings suggest that F0 and intensity are controlled in an integrated fashion to maintain the contrast between stressed and unstressed words. When a cue is impaired through perturbation, speakers not only oppose the perturbation but enhance other prosodic cues to achieve emphatic stress.