This paper presents a compensation study looking at the production of emphatic accent. Studies of motor control reveal a pattern of goal-oriented compensation. In bite-block studies, rapid compensation for perturbation of jaw movement is exhibited in the movement of the lips to achieve closure and of the tongue to achieve appropriate vowel formants. When the movement of one articulator is constrained, the others compensate to achieve the functional target. The multiple joints involved in hand position (shoulder, elbow, and wrist) cooperate in a similar fashion, suggesting that this compensatory behaviour is a general property of skilled action.
In the current study, we investigated the acoustic parameters used to express contrastive emphasis in English. We wished to see whether constraining one acoustic correlate of contrastive emphasis, f0, would elicit a compensatory increase in the other correlates, duration and amplitude. We constrained f0 in two separate manipulations: by eliciting sentences in whispered speech (removing f0 information altogether), and by eliciting pitch accents in the context of sentence-final question intonation (leaving less f0 range available with which to express contrastive emphasis).
The whisper manipulation had no effect on duration or amplitude: they varied with contrastive emphasis by the same magnitude in whispered statements as in normally-spoken statements. The question manipulation showed a sympathetic effect. The f0 correlate of contrastive accent was reduced in questions relative to statements (as expected). Rather than compensating for this loss, both the duration and the amplitude correlates were also reduced in questions. This pattern of sympathetic variation in physically independent parameters does not appear to have a parallel in the motor control literature, either for speech or for other skilled actions.