Motion Capture of Emotional Body Language in Narrative Scenarios

We interact with the world we live in by moving in it. The interaction is versatile and includes communications through speech and gestures, which serve as media to transmit ideas and emotions. A narrator, be it a professional actor on the stage or a friend telling an anecdote, expresses her ideas (the content) and feelings (the emotional colouring) through the choice of words and syntactical structures, her prosody, facial expressions and body language. Our present focus is on emotional body language, which became a field of intensive research several decades ago. Before psychopsysical experiments or trajectory analysis can take place, a set of mocap (motion capture) data has to be accumulated. This can be done with different equipment setups and by now human motion can be captured fairly precisely at a high frame rate. One of the major decisions for the researchers however is the choice of scenarios according to which the actors are to perform motion. This question is especially tricky when we deal with emotions, since the problems of sincerity and naturalness come into play. There are several ways to induce emotions and moods in people, but for motion capture the socalled imagination technique has been used most frequently. The actors are asked to evoke an emotion in themselves by recalling a past event. The main drawbacks of this technique in mocap are the following: (1) it is still impossible to ensure that the emotions are sincere and the motion is natural and not artificial or exaggerated; (2) the emotional categories often rapidly succeed each other in random fashion; (3) the emotional scenarios can be very abstract and taken out of context.We have developed an experimental setup where the emotional body language can be captured in a maximally natural yet controlled manner. The participants are asked to imagine they are narrating a fairy-tale to children. They perform several tasks on the text before their acting in recorded. The setup allows the actors to narrate the story at their own pace, move freely and does not require them to learn the text by heart, yet the recorded data can be easily extracted and processed after the motion capture session. The resulting extracted data can then analysed for various features or used in perceptual experiments