1. MIT Media Lab, Cambridge, MA 02139, USA.
2. Department of Robotic Science and Technology, Chubu University, Kasugai, Aichi 487-8501, Japan.
3. Department of Computing, Imperial College London, London SW7 2AZ, UK.
4. Chair of Embedded Intelligence for Health Care and Wellbeing, University of Augsburg, 86159 Augsburg, Germany.