Speech production is always accompanied by facial and gestural activity. The present study is part of a broader research project on how head movements and facial expressions are related to voice variations in different speech situations. Ten normal subjects were recorded while reading aloud, answering yes/no questions, and dialoguing with an interviewer. Rapid rising-falling eyebrow movements produced by the subjects as they spoke were associated with Fo rises in only 71% of the cases. This suggests that eyebrow movements and fundamental frequency changes are not automatically linked (i.e., they are not the result of muscular synergy), but are more a consequence of linguistic and communicational choices. Note also that 38% of the eyebrow movements were produced while the subject was not speaking. Thus, eyebrow movements may also serve as back-channel signals or play a role in turn-taking during conversation.

Following our work on the relationship between eyebrow movements and the fundamental frequency of the voice, this article presents the results of a study on this phenomenon, and also on the temporal location of rapid eyebrow movements with respect to speaking turns during dialogue. We used an automatic movement-acquisition system coupled with the simultaneous, synchronized recording of the vocal production. This procedure permits an objective analysis of eyebrow movements in relation to the vocal production. The data obtained showed that the speakers' rapid eyebrow movements were associated both with turn-taking (occurring right before or right after speaking turn onset) and with changes in the fundamental frequency. These findings suggest that rapid eyebrow movements are mainly linked to motivation and the intention to communicate, and may also act as a focus marker in speech.

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