About the Authors

Hirokata Fukushima

hirof@ardbeg.c.u-tokyo.ac.jp (HF); khiraki@idea.c.u-tokyo.ac.jp (KH)

Affiliations Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan, Japan Society for Promotion of Sciences, Tokyo, Japan, Department of Psychology, Keio University, Tokyo, Japan

Satoshi Hirata

Affiliation Great Ape Research Institute of Hayashibara Biochemical Laboratories, Inc., Tamano, Japan

Ari Ueno

Affiliations Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan, Department of Human Relations Studies, School of Human Cultures, The University of Shiga Prefecture, Hikone, Japan

Goh Matsuda

Affiliation Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan

Kohki Fuwa

Affiliation Great Ape Research Institute of Hayashibara Biochemical Laboratories, Inc., Tamano, Japan

Keiko Sugama

Affiliation Great Ape Research Institute of Hayashibara Biochemical Laboratories, Inc., Tamano, Japan

Kiyo Kusunoki

Affiliation Great Ape Research Institute of Hayashibara Biochemical Laboratories, Inc., Tamano, Japan

Masahiro Hirai

Affiliations Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan, Japan Society for Promotion of Sciences, Tokyo, Japan, Department of Psychology, Queen's University, Kingston, Ontario, Canada

Kazuo Hiraki

hirof@ardbeg.c.u-tokyo.ac.jp (HF); khiraki@idea.c.u-tokyo.ac.jp (KH)

Affiliation Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan

Masaki Tomonaga

Affiliation Section of Language and Intelligence, Primate Research Institute, Kyoto University, Inuyama, Japan

Toshikazu Hasegawa

Affiliation Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan

Competing Interests

Four authors are employed by Hayashibara Biochemical Laboratories, Inc. However, the company had no role in study design, consultancy, data collection and analysis, decision to publish, or preparation of the manuscript. The authors declare their full adherence to all PLoS ONE policies on data sharing and materials.

Author Contributions

Conceived and designed the experiments: HF SH AU GM MH KH MT TH. Performed the experiments: SH KF KS KK. Analyzed the data: HF. Contributed reagents/materials/analysis tools: HF GM. Wrote the paper: HF SH AU GM MH KH.