1. Synsophy Project, Communications Research Laboratory, Kyoto 619-0289, Japan
2. Graduate School of Information Science, Nara Institute of Science and Technology, Nara 630-0101, Japan
3. Research Center for School Education, Naruto University of Education, Naruto 772-8502, Japan
4. School of International Cultural Relations, Hokkaido Tokai University, Sapporo 005-8601, Japan
5. School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan