1. John A. Paulson School of Engineering and Applied Sciences, Harvard University, Allston, MA, USA
2. Media Lab, MIT, Cambridge, MA, USA
3. Harvard University, Allston, MA, USA
4. Department of Computer Science and Artificial Intelligence, University of the Basque Country, Donostia-San Sebastian, Spain
5. Department of Computer Science, Boston College, Chestnut Hill, MA, USA