[1] Advanced Telecommunications Research Institute International, Kyoto, 619-0299, Japan
[2] Department of Psychology, Queen's University, Kingston, Ont., Canada
[3] ERATO, Kawato Dynamic Brain Project, Kyoto, 619-0299, Japan
[4] ATR Human Information Processing Research Laboratories, Kyoto, 619-0299, Japan
[5] Digital Human Laboratory, National Institute of Advanced Industrial Science and Technology
[6] Human Information Science Laboratories