Head Nodding and Hand Coordination Across Dyads in Different Conversational Contexts

This paper aims to explore what different patterns of head nodding and hand movement coordination mean in conversation by recording and analysing interpersonal coordination as it naturally occurs in social interactions. Understanding the timing and at which frequencies such movement behaviours occur can help us answer how and why we use these signals. Here we use high-resolution motion capture to examine three different types of two-person conversation involving different types of information-sharing, in order to explore the potential meaning and coordination of head nodding and hand motion signals. We also test if the tendency to engage in fast or slow nodding behaviour is a fixed personality trait that differs between individuals. Our results show coordinated slow nodding only in a picture-description task, which implies that this behaviour is not a universal signal of affiliation but is context driven. We also find robust fast nodding behaviour in the two contexts where novel information is exchanged. For hand movement, we found a non-significant trend toward low-frequency coordination during two-way information sharing in the Meal Planning task, but no effects survived correction for multiple comparisons. Finally, nodding varied across contexts, and our exploratory analyses did not provide evidence that it indexes stable individual differences in social traits. We interpret these results in terms of theories of nonverbal communication and consider how these methods will help advance automated analyses of human conversation behaviours.