Hayaki, John Mitani, Linda Marchant, Kazuhiko Hosaka, Akiko Matsumoto-Oda, Michio Nakamura, Noriko Itoh, Tetsuya Sakamaki and Nadia Corp. We are indebted to our field assistants, in particular, Ramadhani Nyundo, Rashidi Kitopeni, Rashidi Hawazi, Mtunda Hawazi, Mosi B. Kasagula, Hamisi B. Kasagula, Mosi Hamisi, Kabumbe Athumani, and Mosi Matumla. We are indebted to Naomi Miyamoto for assistance in editing 212 Discussion video clips. We thank Frans de Waal for constructive comments on this project and Aiko Hiraguchi and Kaoru Hashimoto for encouragement. Field research was supported by funds from the JSPS International Scientific Research Program, Global Environment Research Fund of the Ministry of Environment, the Leakey Foundation, Grant-in-Aid for JSPS Fellows. References Adang OMJ Teasing in young chimpanzees. Behaviour 88:98122 Albrecht H, Dunnett SC Chimpanzees in West Africa. Piper,