1. School of Intelligence Science and Technology, Peking University, Beijing, China
2. Department of Computer Science, University of Manchester, Manchester, U.K.
3. Cognitive Architecture for Collaborative Technologies Unit, Istituto Italiano di Tecnologia, Genoa, Italy
4. Graduate School of Engineering Science, Osaka University, Toyonaka, Japan
5. Department of Information Technology, Uppsala Social Robotics Lab, Uppsala University, Uppsala, Sweden