Head motion during dialogue speech and nod timing control in humanoid robots

Head motion naturally occurs in synchrony with speech and may carry paralinguistic information, such as intention, attitude and emotion, in dialogue communication. With the aim of verifying the relationship between head motion and the dialogue acts carried by speech, analyses were conducted on motion-captured data for several speakers during natural dialogues. The analysis results first confirmed the trends of our previous work, showing that regardless of the speaker, nods frequently occur during speech utterances, not only for expressing dialogue acts such as agreement and affirmation, but also appearing at the last syllable of the phrase, in strong phrase boundaries, especially when the speaker is talking confidently, or expressing interest in the interlocutor´s talk. Inter-speaker variability indicated that the frequency of head motion may vary according to the speaker´s age or status, while intra-speaker variability indicated that the frequency of head motion also differs depending on the inter-personal relationship with the interlocutor. A simple model for generating nods based on rules inferred from the analysis results was proposed and evaluated in two types of humanoid robots. Subjective scores showed that the proposed model could generate head motions with naturalness comparable to the original motions.