About the Authors

Masahiko Morita

mor@bcl.esys.tsukuba.ac.jp

Affiliation Department of Intelligent Interaction Technology, Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Ibaraki, Japan

Shigemitsu Morokami

Affiliation Faculty of Letters, Aichi Shukutoku University, Nagakute, Aichi, Japan

Hiromi Morita

Affiliation Graduate School of Library, Information and Media Studies, University of Tsukuba, Tsukuba, Ibaraki, Japan

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: MM. Performed the experiments: SM HM. Analyzed the data: HM. Wrote the paper: MM. Prepared the figures: SM.