Reactive feedback control and adaptation to perturbed speech timing in stressed and unstressed syllables

Abstract

This study examines speakers’ reaction to focally applied temporal real-time auditory feedback perturbation in a word-initial unstressed syllable (Unstressed condition) and a similar word-medial stressed syllable (Stressed condition) in a three-syllabic word. Speakers compensate locally in both conditions for the perturbed syllable’s nucleus (V; compressed by the perturbation) but not for the complex onsets (CC; stretched by the perturbation). The perturbation of the first, unstressed syllable causes a global slowing down of all segments following the perturbation (syllable two and three), while the perturbation in the Stressed condition elicits local adjustments only in the perturbed (second) syllable. When viewed in a larger prosodic context, the timing strategy in the Unstressed condition indicates that speakers aim to keep relative durations within the word constant when the word-initial onset is auditorily stretched, leading to a compensatory pattern for both CC and V in word-proportional durations. In the Stressed condition, increasing the stressed vowel’s duration seems to be of the highest priority, causing all other segments to take up a shorter portion within the word. Adaptation effects of the stressed vowel indicate a durational representation on the segment level. Further adaptation effects additionally suggest a representation of timing/coordination in larger prosodic units. Complementary investigation of aperiodicity, spectral skewness, and intensity (RMS) indicates that spectral properties can change along with compensatorily increased duration.