1. John A. Paulson School of Engineering and Applied Sciences, and the Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, USA.
2. Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
3. Department of Physics and Munich School of BioEngineering, Technical University of Munich, Garching, Germany.
4. Institute of Robotics and Mechatronics, German Aerospace Center, Oberpfaffenhofen, Germany.
5. Cognitive Robotics Department, Delft University of Technology, Delft, The Netherlands.