Speaker sincerity influences F0-coupled head motion in spontaneous monologues

Abstract

Movements of the head during speech serve multiple communicative purposes, including perceptual enhancement of prosodic F0 contours. However, it remains uncertain how much of any correlation between head movement and F0 may be due to physiological coupling mechanisms exerting effects on glottal tension. In this work, six native speakers of American English (3F) were videorecorded during production of spontaneous monologues lasting 90 seconds. Each speaker extemporized twice on two topics chosen from a list (e.g., "video games waste time"). One of these they agreed with ("sincere"), and the other they pretended to agree with ("insincere"). Speaker head movements were quantified as displacement/rotation of a six DOF rigid body from the videos using OpenFace (Baltrušaitis, 2018). F0 for each speaker was converted to semitones relative to the median value for that speaker. Results show larger semitone excursion range but smaller head movement range for the sincere condition, with no significant differences in syllable rate across conditions. LME models predicting absolute semitone changes from head displacement show significant positive slopes for main effects of movement and sincerity, and an additive interaction for sincere productions. These differences suggest that, while head movement correlates with F0 overall, speaker sincerity can interact with the relation.