Mental effort associated with habitual, breathy, fry, and twang voice quality measured via the Borg CR10 and the NASA TLX

Objective. Patients participating in voice therapy commonly report high mental effort when learning and implementing a novel voice production technique: “I really have to concentrate to do this.” Consequently, they have difficulty practicing and implementing a target voice quality when tired or distracted, or when participating in a conversation that requires attention. Although mental effort plays an important role in voice therapy adherence, it has received little empirical investigation in voice science, and no scale exists to assess it in the voice clinic. Therefore, the purpose of this study was to examine the validity of an adapted Borg CR10 scale in measuring mental effort associated with intentional alteration of voice quality.
Methods/Design: The Borg CR10 was experientially anchored for mental effort. Ten participants were asked to count aloud for 30 second periods in their habitual voice as well in 3 non-habitual voice qualities: breathy, fry and twang. To examine concurrent validity, they completed the single-item Borg CR10 mental effort adaptation and items from the NASA-TLX (an existing 6-item scale) after each voice quality. For discriminant validity, participants also assessed their vocal effort on these scales.
Results: Both vocal and mental effort were consistently rated significantly higher for the three target voice qualities than for habitual voice quality; with significant, strong correlations between the Borg CR10 and NASA-TLX items, indicating good concurrent validity. As evidence of discriminant validity, For discriminant validity, vocal and mental effort were moderately correlated, indicating that these are separate but related constructs, as hypothesized.
Conclusions: the Borg CR10 adaptation for mental effort has potential for use in the voice clinic. Further investigation is needed in the relationship between vocal and mental effort.