The effect of rate reduction on signaling prosodic contrasts in dysarthria

To understand how reducing speaking rate alters prosodic contrasts in speakers with dysarthria (DYS) and healthy controls (HC).

Seven male speakers with DYS (mean age = 34.9) and 7 age- and sex-matched HC (mean age = 36.9) produced identical phrases with affirmative (A), contrastive stress (CS) or question (Q) intonation at habitual and slow rate within a naturalistic game. Relative (word-to-word) changes in peak fundamental frequency (F0), intensity, and duration were compared across conditions, groups, and rates.

For some contrasts, rate reduction differentially affected the speaking groups, with HC exaggerating and speakers with DYS dampening some prosodic cues. Rate reduction diminished the Q contrast for both groups, with reduced peak F0 differences for HC and reduced word duration differences for HC and with DYS speakers. Slow rate also resulted in decreased lengthening of the final word for all three contrasts, thereby diminishing the Q contrast while exaggerating the CS and A contrasts.

Although slow rate may improve segmental intelligibility, it may inadvertently dampen prosodic contrasts for some DYS speakers, thereby impacting communication effectiveness and naturalness. Implications for designing interventions that balance trade-offs between prosodic modulation and segmental clarity are discussed.