Timing of smile suppression during the articulation of labials in smiled speech

Past studies have shown that opposing forces on the lips can be reconciled by suppressing a smile during speech-related lip closure movements [Liu et al., 2020, ISSP]. However, the exact timing of this suppression on the smiling posture remains unknown. The purpose of this study was to determine the onset and duration of smile suppression during labial production in smiled speech. We collected video footage of participants reading sentences that contain labial sounds (/m, f, v, b, p, w/) under three facial posture conditions (neutral, smile, laugh), and extracted short video clips of the labial sound productions. We then analyzed the extent of lip spreading in each facial posture condition using OpenFace 2.0 [Baltrušaitis et al., 2018, IEEE]. Our preliminary results show that smile is suppressed in the smiling and laughing conditions, with attenuation beginning approximately 300ms prior to labial sound production, and continuing for about 600ms regardless of conditions. Further analysis will investigate the duration of suppression after the offset of labials and will be conducted on more participants.