Planning Socially Expressive Mobile Robot Trajectories.

Many mobile robotics applications require robots to navigate around humans who may interpret the robot's motion in terms of social attitudes and intentions. It is essential to understand which aspects of the robot's motion are related to such perceptions so that we may design appropriate navigation algorithms. Current works in social navigation tend to strive towards a single ideal style of motion defined with respect to concepts such as comfort, naturalness, or legibility. These algorithms cannot be configured to alter trajectory features to control the social interpretations made by humans. In this work, we firstly present logistic regression models based on perception experiments linking human perceptions to a corpus of linear velocity profiles, establishing that various trajectory features impact human social perception of the robot. Secondly, we formulate a trajectory planning problem in the form of a constrained optimization, using novel constraints that can be selectively applied to shape the trajectory such that it generates the desired social perception. We demonstrate the ability of the proposed algorithm to accurately change each of the features of the generated trajectories based on the selected constraints, enabling subtle variations in the robot's motion to be consistently applied. By controlling the trajectories to induce different social perceptions, we provide a tool to better tailor the robot's actions to its role and deployment context to enhance acceptability.

Exploring the determinants of the graded structure of vocal emotion expressions.

We examined what determines the typicality, or graded structure, of vocal emotion expressions. Separate groups of judges rated acted and spontaneous expressions of anger, fear, and joy with regard to their typicality and three main determinants of the graded structure of categories: category members' similarity to the central tendency of their category (CT); category members' frequency of instantiation, i.e., how often they are encountered as category members (FI); and category members' similarity to ideals associated with the goals served by its category, i.e., suitability to express particular emotions. Partial correlations and multiple regression analysis revealed that similarity to ideals, rather than CT or FI, explained most variance in judged typicality. Results thus suggest that vocal emotion expressions constitute ideal-based goal-derived categories, rather than taxonomic categories based on CT and FI. This could explain how prototypical expressions can be acoustically distinct and highly recognisable but occur relatively rarely in everyday speech.

Multimodal indices to Japanese and French prosodically expressed social affects.

Whereas several studies have explored the expression of emotions, little is known on how the visual and audio channels are combined during production of what we call the more controlled social affects, for example, "attitudinal" expressions. This article presents a perception study of the audovisual expression of 12 Japanese and 6 French attitudes in order to understand the contribution of audio and visual modalities for affective communication. The relative importance of each modality in the perceptual decoding of the expressions of four speakers is analyzed as a first step towards a deeper comprehension of their influence on the expression of social affects. Then, the audovisual productions of two speakers (one for each language) are acoustically (F0, duration and intensity) and visually (in terms of Action Units) analyzed, in order to match the relation between objective parameters and listeners' perception of these social affects. The most pertinent objective features, either acoustic or visual, are then discussed, in a bilingual perspective: for example, the relative influence of fundamental frequency for attitudinal expression in both languages is discussed, and the importance of a certain aspect of the voice quality dimension in Japanese is underlined.