Analysis of Human Nodding Behavior during Group Work for Designing Nodding Robots

Nodding has various communicative functions in humans, such as agreement, emphasis and turn-taking and can also create various positive impressions in communication by the person exhibiting the behavior. The ultimate aim of our research is to facilitate communication by implementing nodding behavior in robots. This study analyzed videos of human conversations in groups and focused on three aspects of people's nodding behavior as they listened to others: 1) Time period to complete a nodding cycle and each nods, 2) Time delay before initiating a nodding response, and 3) Number of continuous nods used at one time. We found that: 1) The mode time period to a nod was 0.27 s, with 96% of all nods occurring within 0.17~0.57 s. 2) The mode time delay before initiating a nodding response was 0.30 s, with 95% of all nods occurring within -0.78~1.4 s. 3) Fewer than six continuous nods were used 97% of the time - one nod, 55%, two nods, 24%, three nods, 12%, four nods, 3.0%, and five nods, 2.1%. Ultimately, the research findings serve as guidelines for implementing accurate human nodding behavior in robots.