Vocal effort modulates the motor planning of short speech structures

TL;DR

This study investigates how vocal effort influences the timing of motor planning in speech, showing that increased effort extends planning delays, especially for plosive consonants, through experimental and modeling approaches.

Contribution

It demonstrates that vocal effort modulates speech motor planning timing, providing new insights into the relationship between effort and speech production.

Findings

Delays in speech onset correlate with transition durations for plosive consonants.

Vocal effort impacts the timing of motor planning in speech sequences.

Mathematical models support effort as a key factor in speech motor planning.

Abstract

Speech requires programming the sequence of vocal gestures that produce the sounds of words. Here we explored the timing of this program by asking our participants to pronounce, as quickly as possible, a sequence of consonant-consonant-vowel (CCV) structures appearing on screen. We measured the delay between visual presentation and voice onset. In the case of plosive consonants, produced by sharp and well defined movements of the vocal tract, we found that delays are positively correlated with the duration of the transition between consonants. We then used a battery of statistical tests and mathematical vocal models to show that delays reflect the motor planning of CCVs and transitions are proxy indicators of the vocal effort needed to produce them. These results support that the effort required to produce the sequence of movements of a vocal gesture modulates the onset of the motor plan.